Really poor performance form my 5.7 Mercruiser Horizon MPI - Only just started.....

[davus]

Hi All!

Dave here from Australia.

Ive recently purchased a 7.1 meter Whittley Cruisemater, an Australia built boat, and im now having trouble with holeshot / engine performance. Its a long story, and i've tried a whole bunch of things.

Im mechanically minded, but have not worked on boat motors before.....

I love mechanical work, and love getting my hands dirty. Ill always do as much work on my boat / car myself as i can. I find it very rewarding.

Im hoping to take a moment of your time to give you some background info, and a description of the problem im having.

I bought the boat second hand from a private seller in Australia. It is 7.1 meters long, and is powered by a Mercruiser 5.7 MPI Horizon motor with a Bravo 3 leg. The props (i believe) are 20 inch pitch. The boat itself when fully loaded is a shade over 2 ton from what i can figure out. The engine is cooled via a closed cooling system with heat exchanger.

I have only owned it for about 6 weeks, and have only been out in it twice (apart from the test drive i did, which was extremely short due to the wether).

My family and I took it out for our first outing about 4 weeks ago. We took off cruising at about 30 knots or so. We got about 15 minutes into our journey when the engine overheated. Stopping to check the issue, I found water spraying out of a cracked starboard exhaust manifold. The higher the RPM, the more water we brought on. So we just putted around near shore for the day allowing the bilge to empty out as we went. The engine did not overheat whilst bobbing around at about 5-7 knots. It was quite manageable.

I did a bit of research and came across "high speed overheating"...which seemed to exhibit overheating at high speeds when the exhaust risers were old and clogged with rust. Obviously directly related to RPM and the volume of water being pumped through the raw water cooling system. Indeed i pulled the risers and manifolds off and found them to be in bad shape, so bought brand new OEM mercruiser risers and manifolds for both sides.

While i had the manifolds off, i noticed the exhaust flappere were missing. I presumed they were stuck in the y pipe. I removed the bravo three leg and sure enough there they all were. I hoped this would also contribute to my overheating issue. I cleaned everything up, and put the leg back on........

So then last weekend we took the boat out again, and ended the day with two problems. I still had my overheating issue (bugger!), and now to add to insult, the holeshot is complete garbage (about 30 seconds to get out). Its actually that bad that i dont think id get a skier out of the water at all, and i had to get the wife and kids to move to the front to try and help the nose get down. When getting out of the hole I am trimming right down, and ensuring my trim tabs are not down.

So again i brought the boat home and did a bit of brainstorming as to what the issues could be.

Tackled cooling first. I decided it would either be the raw water impellor (but doubfull of this given we were not overheating at lower speeds), or something wrong with the heat exchanger. I took the raw water impellor out and it was fine......infact almost brand new (which actually gave me a clue). To me, it seemed as though other parts of this boat have not been maintained properly, so I asked myself "why is the raw water impellor in such good condition?".

I tool the end caps off the heat exchanger, and to my delight i found the inlet to be almost completely blocked with fragments and chunks of old raw water impellor. I cleaned it out and put it all back together. I am yet to take the boat back to the water, but i am very hopeful that this was playing a large role in the overheating. Logically it make sense.

So, that brings me to now.

Im hoping someone can give me some advice on why it might be taking so long to get out of the hole, and why the engine performance seems so poor. I have come up with a few theories, but because im so new to boating with a larger boat, im really looking for some guidance and help.

I have done a compression test of the engine, and all cylinders are between 190-200 PSI with the exception of one that is a touch above 140 PSI. Whilst this is not a good thing, i dont think it would be causing my holeshot issues would it? Ive done a leakdown test and confirmed the issue is compression rings.

I have done a fuel pressure test ( not under load of course). Oddly the fuel pressure only get to about 23-25 PSI at idle, and about 28 PSI while cranking. Ive read a number of threads on various websites.......some seem to say these 5.7 V8 are meant to be about 45 PSI, and some are meant to be about 25 PSI. Not sure which is which.?

I have changed all plugs for new NGK Iridium plugs, and have changed all ignition leads for brand new ones.

I have inspected / cleaned the rotor button and distributor cap. The distributor has minimal shaft play. It does however have a vacuum line connector off it that has nothing plugged into it?. Vacuum advance that is not needed?

Last night i had a bit of a brainwave after reading some other forums......and id really love someones advice?. I didnt realise that these engines have a guardian mode. Is it possible that due to the overheating the engine went into guardian mode, and thats why my power was way down? It would seem odd to me given that during the second outage i stopped and started the boat quite a number of times. Not sure if this clears a guardian mode.....?.

Working through the seires of events.....

1) Take the boat out on day 1.
2) Accelerate to full power and boat performs fairly well out of the hole.
3) After 20 minutes boat engine overheats.
4) pulled back and temp came back down again.
5) putted around for the rest of the day at no more than about 20% throttle. No other problems.
6) took the boat out of the water and took it home.
7) changed out manifolds, risers, and exhaust flappers.
8) removed outdrive and removed broken exhaust flappers, then replaced outdrive.
9) put boat back in water and accelerated to full throttle. Immediately noticed sluggish behavior. (remembering the last overheating had been a week before on the prior trip)
10) Even with sluggish behavior still got out of the hole (just!). Engine overheated again after about 7-8 minutes of 25~ knots. I did NOT get an audible alarm, but the light on the dash did come on.
11) slowed right now and waited for engine to cool down.
12) Accelerated again and still had extreme sluggishness.
13) temp started coming back up, and wether was very choppy
14) Call it early and took boat out of water and came home.

So theoretically, IF the motor has gone into guardian mode on the first trip........and IF it requires a service cetner to clear the guardian mode, then could this be my problem?. Or am i way off the mark here? Ive heard of some people clearing it by disconnecting the battery for a few hours. Ive heard of epople having to key start it a number of times before the problem went away, and ive heard of people having to take it to a shop to get cleared. ????

I have made a call to buy rinda diacom pd for it.........but it wont be here for some weeks, and im keen to try and take it out this coming weekend.

So - taking all the above into consideration........can anyone lend a hand as to what might be wrong???.

Thanks so much for any help in advance.

Dave

 

[Fun Times]

Hi there, welcome to iboats!

What year is the engine? Better yet, do you have the engine serial number handy?

 

[davus]

hey Fun Times!..

Thanks for your reply mate

Im not sure what year the engine is (although i would love to know!) ........

The serial number is 0M093415

 

[Fun Times]

I removed the bravo three leg and sure enough there they all were. I hoped this would also contribute to my overheating issue. I cleaned everything up, and put the leg back on........So then last weekend we took the boat out again and the hole shot is complete garbage (about 30 seconds to get out). Its actually that bad that i don't think id get a skier out of the water at all, and i had to get the wife and kids to move to the front to try and help the nose get down. When getting out of the hole I am trimming right down, and ensuring my trim tabs are not down.

One of my first thoughts is maybe you put the celery stick in the wrong position during reinstallation of the drive as that would affect hole shot. The following link will help show you the correct position for celery stick installation, http://www.boatfix.com/merc/Bullet/98/98_16.pdf

Also while you're checking the celery stick installation, you'll want to ensure that the trim rams are not turned 180 degrees out as it could have a very slight affect on hole shot.
In Mercruiser service manual #11, you will want to read sections 5-B page 18 as it shows you the correct way to place the trim rams ends and inner trim rams. http://www.boatfix.com/merc/Servmanl/11/11b5r5x.pdf ....If the "pages" aren't readable, find step 15. Position trim cylinder rear connecting ends as shown near the bottom of the link.

I took the end caps off the heat exchanger, and to my delight i found the inlet to be almost completely blocked with fragments and chunks of old raw water impellor. I cleaned it out and put it all back together. I am yet to take the boat back to the water, but i am very hopeful that this was playing a large role in the overheating. Logically it make sense.

That's a good sign... If it continues to overheat and if you haven't already be sure to back flush the cooling system in case there is anymore debris anywhere else.

I have done a compression test of the engine, and all cylinders are between 190-200 PSI with the exception of one that is a touch above 140 PSI. Whilst this is not a good thing, i don't think it would be causing my hole shot issues would it? I've done a leak down test and confirmed the issue is compression rings.

Doesn't sound like it at this point.

I have done a fuel pressure test ( not under load of course). Oddly the fuel pressure only get to about 23-25 PSI at idle, and about 28 PSI while cranking. Ive read a number of threads on various websites.......some seem to say these 5.7 V8 are meant to be about 45 PSI, and some are meant to be about 25 PSI. Not sure which is which.?

We'll need your exact engine info to know this. But I'd also recommend a new fuel filter to help rule anything out...This will also allow you to inspect the fuel's condition for water or debris.

I have changed all plugs for new NGK Iridium plugs, and have changed all ignition leads for brand new ones.

What spark plug part number did you put in and take out?

I have inspected / cleaned the rotor button and distributor cap. The distributor has minimal shaft play. It does however have a vacuum line connector off it that has nothing plugged into it?. Vacuum advance that is not needed?

Sounds like the vent found on some Mercruiser distributor cap models. If not, we'll need a photo of this.

Last night i had a bit of a brainwave after reading some other forums......and id really love someone's advice?. I didn't realize that these engines have a guardian mode. Is it possible that due to the overheating the engine went into guardian mode, and that's why my power was way down? It would seem odd to me given that during the second outage i stopped and started the boat quite a number of times. Not sure if this clears a guardian mode.....?.

On whatever MPI system you have and if your engine model has it programed into the ECM, the guardian mode should only be activated while the problem is happening...If the problem repairs itself after either returning to idle or engine shut down/key off then the engine should return to normal even if you find it stored in the ECM later on using a scan tool. Clearing the ECM history isn't "really" necessary should the problem correct itself. The scan tool you're about to buy will clear the history without the need for a dealer to clear it.

10) Even[ with sluggish behavior still got out of the hole (just!). Engine overheated again after about 7-8 minutes of 25~ knots. I did NOT get an audible alarm, but the light on the dash did come on.

You'll want/need to confirm that the warning horn system is working correctly by preforming a ground test on one of the sensors. Do you hear a beep at key up? Some engine models offer that feature while some do not.

 

[Fun Times]

hey Fun Times!..

Thanks for your reply mate

Im not sure what year the engine is (although i would love to know!) ........

The serial number is 0M093415

What year is the boat? your engine is a MERCRUISER 350 BRAVO HORIZON 350 MAG BRAVO MPI

The serial number seems to put the year between 2000-02 ish.

Your fuel pressure regulator should put your PSI right at 30 PSI. You have a MEFI 3 ECM.

Also did you remove the props when you took the drive off of the boat?

 

[davus]

One of my first thoughts is maybe you put the celery stick in the wrong position during reinstallation

Just went and had a look at the celery stick to ensure i put it back in the right way, and it is correct. It is positioned as per the bulletin.

Also while you're checking the celery stick installation, you'll want to ensure that the trim rams are not turned 180 degrees out as it could have a very slight affect on hole shot.

I didnt take the rams off completely. I just removed the end off the outdrive leaving hydraulics etc all hooked up. From this i assume they can only go back on one way

That's a good sign... If it continues to overheat and if you haven't already be sure to back flush the cooling system in case there is anymore debris anywhere else.

No problems, great idea. Will see how the overheating goes on the next trip.

Doesn't sound like it at this point.

Good news. I didnt think it would be a major issue either.
Thanks Fun Times - your help is very much appreciated.

We'll need your exact engine info to know this. But I'd also recommend a new fuel filter to help rule anything out...This will also allow you to inspect the fuel's condition for water or debris.

Are you able to tell any more about my engine from the serial number in my previous post?. Id love to know where i can look up the year etc.

You wouldnt happen to know any way of easily getting to the fuel filter? My understanding is that it has a cool fuel system. where is the fuel filter. Is this the unit at the front of the engine on the starboard side? Its in an enclosure that says "do not step"

What spark plug part number did you put in and take out?

The plugs that came out of it were NGK TR5IX. I put these same plugs back in.

Sounds like the vent found on some Mercruiser distributor cap models. If not, we'll need a photo of this.

This isnt my cap off my motor - but this is the exact same type of cap.

On whatever MPI system you have and if your engine model has it programed into the ECM, the guardian mode should only be activated while the problem is happening...If the problem repairs itself after either returning to idle or engine shut down/key off then the engine should return to normal even if you find it stored in the ECM later on using a scan tool. Clearing the ECM history isn't "really" necessary should the problem correct itself. The scan tool you're about to buy will clear the history without the need for a dealer to clear it.

Sounds like hopefully i dont need to take it to someone. Hopefully the combination of me turning it off, disconnecting the battery etc should clear this if it was contributing.

You'll want/need to confirm that the warning horn system is working correctly by preforming a ground test on one of the sensors. Do you hear a beep at key up? Some engine models offer that feature while some do not.

I believe it is. I do hear beep at key up, and in fact now that i think about it, when i did the sea test there was a beep when the engine overheated.......so yes, i believe the warning system is working. It seems however that the siren goes off later than the warning light?. When i took it out the other week, the temp light came on, but the warning beep didnt go off.

Thanks heaps Fun Times. I really appreciate your efforts.

Dave

 

[davus]

hello again

The boat itself is 2001 - however i was under the impression it was repowered. Perhaps not?

When the boat it running, the fuel pressure is definately not getting to 30 PSI - its more like 21-24 PSI.

Where did you get that info on my motor?

Nope - when i took the leg off i left both props on.

Dave

 

[Tail_Gunner]

I beleive you way under in fuel pressure give me a sec..TBI is 30lbs and i am quite sure mpi is 42 That is a horizon engine a bit of a weird duck...opps 30 is small blocks and 42 big block's

https://drive.google.com/file/d/0B3w...Z2s/edit?pli=1

 

[davus]

so from this, given that I have a small block, it seems as though my fuel pressure is almost right. Its not getting to 30 PSI at idle, but then again I haven't taken it for a sea trial with the fuel pressure gauge hooked up.......so it might increase once the load / vacuum comes up a bit?

Cheers

Dave

 

[Tail_Gunner]

Your first stop is 30lbs on the pressure rail...21/24 is almost 30% under pressure and that's unacceptable. Use the link shown above to identify your system and problem solve. It appear's your fuel pump is bad but check three time's and replace once....it's electrical vacum will have no effect on fuel pressure.

If your getting 21/24 at idle it should be or could be worse at 3000 rpm that would cause a severe lean burn.

 

[davus]

thanks Tail_Gunner

Does anyone have any fancy ways of trying to remove the fuel pump?. Its right under the motor and access is a B$%@H!

Dave

 

[Fun Times]

The boat itself is 2001 - however i was under the impression it was repowered. Perhaps not?

The serial number puts your engine in the 2001ish range so that's the guide to follow at this point.
You mentioned above that the fuel filter is covered in a black box? That seems to indicate the engine could be just a little bit older since merc used the filter cover between1997 - late 99 I believe it was...Maybe 2000 too.

The fuel filter will be down low on the starboard front side and it will look like a oil filter.

Where did you get the serial number from? On top of the engine/flame arrestor cover area or a metal tag just above the engine starter? You'll want to look at both just in case. Also we'll need a photo of your ECM to see what design you have.

When the boat it running, the fuel pressure is definitely not getting to 30 PSI - its more like 21-24 PSI.

You'll need to be closer to 30 psi. One test to see if the regulator is working is to remove the vacuum hose either at or near the regulator area and see if the PSI goes up roughly 3-5 psi...The pressure should jump up with the engine running and disconnecting the fuel pressure regulator vacuum hose. The regulator is next to the fuel pump.

Also by blocking off the fuel return line between the fuel regulator and fuel filter base assembly, would test to see if the fuel pump is capable of producing the fuel pressure needed to run the engine properly.

Where did you get that info on my motor?

There's a few online websites that help tell what engine you have as long as we have the full engine, stern drive, or transom assembly serial number depending on what we're working with.

Nope - when i took the leg off i left both props on.

Okay, I was thinking maybe the dual propeller timing was off a bit had you removed them. In some cases, prop timing has been known to affect boat performance.

When I mentioned the cylinder trim rams being 180 out, it's possible for the inner rams to turned even if you didn't fully remove the whole trim cylinder assembly from the boat.. The area to look at would be where the rear cross pin would need to be removed in order to remove the drive. Where item number 20 slides through.
http://www.mercruiserparts.com/Show_...YDRAULIC+HOSES

so from this, given that I have a small block, it seems as though my fuel pressure is almost right. Its not getting to 30 PSI at idle, but then again I haven't taken it for a sea trial with the fuel pressure gauge hooked up.......so it might increase once the load / vacuum comes up a bit?

It should stay close to 30 psi. Before your next trip out, you might want to get an small external fuel tank supply with an outboard fuel primer bulb and see if you get your fuel PSI and performance back. Also try using the primer bulb to put some pressure to the fuel pump and watch the fuel PSI gauge to see if it helps any during all your testing methods.

Does anyone have any fancy ways of trying to remove the fuel pump?. Its right under the motor and access is a B$%@H!

If you have some room to work with down there but need just a bit more, try unbolting the fuel pump bracket assembly from the motor mount and let it hang down lower in the bilge area of the boat.. It's helped me more then once.

Here are your two potential parts catalogs for your engine models that you may have. One is for your engine serial number and the second one would be for the older engine model it kind of sounds like you have.

What parts you should have,
http://www.mercruiserparts.com/selec..._nbr=809488+99
What parts you may have,
http://www.mercruiserparts.com/selec..._nbr=809488+98

PS,^^^ whatever parts catalog you need, the fuel pressure would be the same regardless.

And yes, that is what your distributor cap from Merc should look like with the vent fitting. No hose connects to it though.

Keep us updated and good luck.

 

[achris]

Hi Dave,

Chris is Perth. If you're also in Perth (but, I suspect you're in Melbourne) I can get to you with the Diacom software and do a code read.

First thing I noticed it you took out and put in the wrong spark plugs. Those engines require NGK BPR6EFS, not TR5IX....

But also you need to find out why the fuel pressure is down so far. It does need to be at 30psi. The injectors see that pressure and if it's not there, not enough fuel will be delivered. The fuel filter should be at the front of the engine, low down on the starboard side. It may have some covers on it...

Chris..........

 

[Fun Times]

First thing I noticed it you took out and put in the wrong spark plugs. Those engines require NGK BPR6EFS, not TR5IX...

Thanks Chris, I meant to address this too.

The 5 is actually one plug hotter than what should be in there. It should be a 6 which is cooler than 5.

When looking up other plugs that could work, TR6IX is the one to try....But you're much better off using/sticking with BPR6EFS as it's more affordable and more designed for your engine model.

Here's what looking at the NGK website says,
MERCRUISER 350 Mag MPI Gen+ (0F602000-0M320489) Stern Drive 8 cyl Chevrolet Small Block

Spark Plug

Part No.

Stock No.

Plug Gap

Photo

Standard	BPR6EFS​	3623​	​	​

Spark Plug	Part No.	Stock No.	Plug Gap	Photo
G-Power	TR6IX​	3689​	​	​

 

[davus]

You mentioned above that the fuel filter is covered in a black box?

Yeah its on the starboard side, near the front of the motor with the words "do not step" on it.

The fuel filter will be down low on the starboard front side and it will look like a oil filter.

yepo - found it - thanks

Where did you get the serial number from? Also we'll need a photo of your ECM to see what design you have.

The serial number on the engine cover, matches the serial number on the block just above the starter

You'll need to be closer to 30 psi. One test to see if the regulator is working is to remove the vacuum hose either at or near the regulator area and see if the PSI goes up roughly 3-5 psi...The pressure should jump up with the engine running and disconnecting the fuel pressure regulator vacuum hose. The regulator is next to the fuel pump.

Looks like i must have to bite the bullet and start pulling the pump out. Is the regulator before or after the fuel rail? Im used to working on systems where the pump sucks fuel out of the tank, through the filter, into the pump, out of the pump into the rail, and then through the regulator - effectively providing the restriction to build the backpressure.

There's a few online websites that help tell what engine you have as long as we have the full engine, stern drive, or transom assembly serial number depending on what we're working with.

Are these classified websites? . I did find this one -> http://www.boats.net/parts/search/Merc/Mercruiser/parts.html but it doesnt seem to mention anything about Horizon, nor the year of my engine when i enter the serial.

it should stay close to 30 psi. Before your next trip out, you might want to get an small external fuel tank supply with an outboard fuel primer bulb and see if you get your fuel PSI and performance back. Also try using the primer bulb to put some pressure to the fuel pump and watch the fuel PSI gauge to see if it helps any during all your testing methods.

If you have some room to work with down there but need just a bit more, try unbolting the fuel pump bracket assembly from the motor mount and let it hang down lower in the bilge area of the boat.. It's helped me more then once.

Again - looks like i am going to have to just resign myself to trying to get the pump out

Here are your two potential parts catalogs for your engine models that you may have. One is for your engine serial number and the second one would be for the older engine model it kind of sounds like you have.

What parts you should have,
http://www.mercruiserparts.com/selec..._nbr=809488+99
What parts you may have,
http://www.mercruiserparts.com/selec..._nbr=809488+98

PS,^^^ whatever parts catalog you need, the fuel pressure would be the same regardless.

Cool - thanks

And yes, that is what your distributor cap from Merc should look like with the vent fitting. No hose connects to it though.

At least something is right!!!

Hi Dave,

Chris is Perth. If you're also in Perth (but, I suspect you're in Melbourne) I can get to you with the Diacom software and do a code read.

First thing I noticed it you took out and put in the wrong spark plugs. Those engines require NGK BPR6EFS, not TR5IX....

But also you need to find out why the fuel pressure is down so far. It does need to be at 30psi. The injectors see that pressure and if it's not there, not enough fuel will be delivered. The fuel filter should be at the front of the engine, low down on the starboard side. It may have some covers on it...

Chris..........

Thanks very much chris!. Indeed I am in melbourne .

Ill order some of those plugs and swap them over, however i do keep coming back to the notion that the boat did actually work fine with these plugs in it.......???

Thanks guys.

I do like a challenge, but im starting to get to the end of my tether!!

Dave

 

[davus]

just a quick update.......

I have ordered 8 X BPR6EFS plugs. Delivery in 3 days.

I took the fuel filter off, and emptied it out. Fuel inside didnt look dirty, not too many particles, and no water.

Interestingly, when i put it back on (after i figured out it had to be primed??).....and put the key on accessories the fuel pressure got to spot on 30 PSI. Then when i started it, it fell down to about 23-25. When i gave it a good rev, it bounced up to about 26-27 PSI.

Got dark before i could do anything else.....

Dave

 

[achris]

Now, that starting to sound like a restriction in the supply side. If you can, put a vacuum gauge between the engine and the tank. You don't want to pull any more than 2" of vacuum (at any revs). If you do, start looking for a restriction.... If you don't have a vac gauge or any place to put it, take an outboard engine remote tank out with you and hook that up and see how you go. One other possibility could be if this engine has a boost pump. If it's not working properly, that would also cause the problem you're experiencing...

I know where the "end of my tether is" ... 1600m from the TMS (Tether Management System)..

 

[aerobat]

like mentioned before the guardian should clear itself when the problem is gone. do you have smartcraft instruments and can red the waterpressure ?

i would recommend to start the easy things :

-make sure you have correct plugs
-change fuelfilter
-verify that after you worked on the manifolds you did not messed up the thrlottle linkage - check if full throttle on the lever is also full throttle on the throttle body on the engine.

and check again.


regarding fuelpump /fuelfilter : do you have the fuelcooling system ? maybe its clogged with debris and creates a vapor lock ? if you have a fuelcooler and really want to take it out it works best when you first remove the raw waterpump starbord lower side .

best

 

[davus]

hi guys

achris - I don't have a vac gauge unfortunately, I do have a few good quality petrol containers - so for the purposes of testing on land I might use one of those. I have no idea if the engine has a boost pump? Do you mean a pre pump?.

Im trying to find a way to get into this tank and inspect the pickup......but it seems no small feat to access it!.

aerobat - Nah I don't have smartgauges . Ive replaced plugs and leads, and have checked throttle travel compared to the throttle lever. The butterflies on the TB are certainly openall the way when the throttle lever is fully depressed.

I do have the coolfuel system. I have replaced the fuel filter, and hopefully tonight will be pulling the fuel pump out for inspection, and possibly to hook it up to a different fuel source. For some reason im not convinced that my poor fuel pressure would be causing the sluggish behavior, but im out of ideas at this stage. The engine doesn't miss a beat....no backfiring, no popping, no hesitating.......just a lack of power.

anyone want to buy a cheap boat??! LOL

Dave