Mercruiser 350 MAG MPI - Ticking / Clicking Sound on idle - No power/Not Rev more than 3000 RPM for first 7-10 minutes

[benchircop26]

Mercruiser 350 Mag MPI - Not Rev more than 3000 RPM for first 7-10 minutes

Hi there, i have a Sea Ray 260 Sundancer powered by a Mercruiser 350 Mag MPI 2005. Last year i had some trouble with the engine as it wasn't revving enough and i had to re-boar cylinder heads, etc, etc. Afterwards engine was working perfectly and was very powerful. After 2 weeks or so i had a vibration coming from the sterndrive and to cut the story short i had to change the U-joints. From then on i have this new problem. Once i try to go on plane, engine won't rev more than 3000RPM. Boat will not plane. Engine will keep fluctuating revs, backfiring and also misses for about 7 - 10 minutes. After these 10 minutes the engine will start to get higher revs and working good but there is still a slight missing noise coming from the engine. If i use the boat again on the same day in a span of 5-8 hours it will work normal from the beginning.

Mercruiser professional checked it with the computer and told me that there are no faults. Would really appreciate your help.

 

[alldodge]

It could be as simple as a distributer cap. The reason I bring this up is because you have the crab style cap (most call them crap caps). The caps can look great and most do, but they can start causing misfiring. Not saying this is the issue, just been to many times that was the issue.

Don't think its fuel right now because it goes and comes. That said have you changed the fuel filter this season?

After this, where going to need to check for loose or corroded connections

 

[benchircop26]

Hi AllDodge, thanks for your reply. i will be going back on the boat tomorrow and check the distributor cap. this season i did not change the fuel filter as i changed it last year end of season. But could it be from the fuel side ? As at the beginning the boat was working fine. I was also going to try to feed fuel from a separate tank and also put injector cleaner in it. What do you think ? Will keep you updated. Thanks

 

[alldodge]

It might be fuel, only way to tell is put a gauge on the fuel rail. But still with it being back-n-forth I'm leaning electrical until we get more info.

As before the cap can look great and still be bad, there is no way to tell. As before not saying it is, there is just no signs to know if it is or not

 

[benchircop26]

Hi AllDodge, i went yesterday and changed the distributor cap and rotor and also noticed that the high tension wire from the cap to the coil wasn't that good. i replaced it and solved the problem. The only bad thing that is happening now is that when its revving from 2000 - 3000 its misfiring a lot but then once i acceed 3000 RPM it works great. Thanks a lot for your help

 

[alldodge]

Sounds good

The 2 to 3K rpm misfire might be fuel pressure or vacuum leak related.

 

[benchircop26]

Mercruiser 350 MAG MPI - Ticking / Clicking Sound on idle - No power/Not Rev more than 3000 RPM for first 7-10 minutes

Hi there, last week i when to use the boat as usual and when i started the engine i was listening to a ticking (clicking noise). I tried to diagnose the problem and it sounded that it was coming from the cylinder head area. When i removed one of the high tension wires from starboard side the noise stopped. i put it back again and there it was again. i went to give it a try and the engine was without power and working/sounding very very bad (could not even plane). Today i went on the boat removed all plugs and did a compression test to my surprise all 8 cylinders were 8.5 bar only (2 months ago i did the compression test and were all 10 bar or more). Please note that before this season i opened both cylinders heads, rebored valves etc, etc. What could be the problem please ??? Would really appreciate you help.

 

[79_banshee]

Valve set maybe needed.

 

[alldodge]

Howdy

Don't know if it was a Moderator or not, but your posted started on this thread
http://forums.iboats.com/forum/engin...t-7-10-minutes

which was your previous thread, but then moved here.

I this first thread you discussed some missing going on between 2000 and 3000 rpm. This previous missing if not fixed could have been your motor running lean and now you have damage to the motor. The lean condition would have come from a vacuum leak or lower fuel pressure. This is probably confirmed by the lower compression numbers your seeing now.

Pulling a plug wire off and the ticking stopped would make me think you have a valve which is damaged. Going from 10 bar (145 psi) to 8.5 bar (123 psi) is quite a drop

 

[benchircop26]

Thanks all for the reply. AllDodge i didn't solve the problem i have with the missing going on between 2000 and 3000rpm. Tomorrow Mercruiser mechanic is coming to check the engine out. Hope he will solve all the problems. Will keep you updated

 

[benchircop26]

HI there, last Saturday Mercruiser mechanic came to see the engine. the clicking was just the manifold exausth gasket. Today i've changed it and he had to come again to check regarding lack of power issues. I tried to go again for a ride and at first it worked good (but some backfiring) after i stopped at idle and tried to plane again... the engine started to work very bad again and also not revving more than 3200 (not planning). Would really appreciate your help. Thanks.

 

[alldodge]

I'll go back to previous post, you mentioned you only have 8.5 bar compression, with that low a compression you have lost about 1/2 the HP in that cylinder. The backfiring means you have an intake valve either not fully closing (from incorrect timing or damage to a valve)

GA_Boater could you merge the topic in my post above with this one? Don't know why it was separated but was thinking it should be together.

 

[79_banshee]

Backfiring sounds like a spark or plug issue. I would check or change plugs look over all the wires make sure nothing has rubbed through and take the distributor cap off and check the connections for corrosion. Have you done any of this on this engine lately. I had a 98 gm with the 350 and it was backfiring and running like crap so I took it to a buddy that had the computer to time it cause it was electronically timed but he said it was dead on. It would really run like crap and backfire when the rpms got up around 2700-4000. Once I got home I started to look over everything and notice the distributor cap was cracked at the #1 plug wire when I tryed to pull it off it completely broke. Upon inspection of that cap it looked like the pin that the roter turns on was corroded up pretty bad. Took the cap off and cleaned up an old one I had and put that on as I was tracing my plug wires I was checking to make sure they where on the right plugs the #7 pushed on a little farther on to the plug and clicked. Started the truck and ran like a dream. I also had an s10 with the 4.3 in it and the roter was so worn it would backfire and was real hard to start. Put a new cap and roter on it and that solved that problem. So I would check that over before spending a bunch of money on it.

 

[GA_Boater]

GA_Boater could you merge the topic in my post above with this one? Don't know why it was separated but was thinking it should be together.

AllDodge


Merged the two topics, AD. Thanks. I merged the earlier topic into this one and modified the thread title. Everything is one topic and the post dates look out of sync, but all comments are in this one thread now. So hopefully less confusing.

The OP, benchircop26, started this second topic and cross posted in both. That's how they got separated.

 

[79_banshee]

The distributor bolt may have backed out a bit and the distributor may have turned knocking it out of time. The truck would do that from time to time. I know this is not a truck but the short block of the engine is the same

 

[benchircop26]

Thanks all for your messages. about 2 months ago i changed the distributor cap and also the rotor so they are brand new. The other mystery is that the engine at the beginning is revving normal up to almost 4800rpm. But then once i will put it on idle and try to plane again engine will start to work very badly. if there is a spark or a plug which are not working properly i assume they wont work good from the beginning..... i had some water intrusion could it be a sensor which got wet and is putting the engine on safe mode ?

Thanks in advance

 

[alldodge]

A sensor can cause the motor to be in power reduction mode. but the sensor going on off from water I don't see it.

When I first looked at the issue I was thinking electrical, not with the lower pressure, backfire as motor rpm's come up I'm going toward fuel. Need to check fuel pressure and place a vacuum gauge between the intake and fuel pressure regulator.

Do you know your serial number?

 

[79_banshee]

And if it was a sensor it should through a code. You had said in an earlier post that the mechanic said there was no codes showing

 

[benchircop26]

No Title

Hi there, thanks for your help. Mechanic didn't have time till date to come and check the engine. Today i've noticed a very important thing, that the compression tester i did the test with was faulty and hopefully compression is not the issue of the engine. I went to do a vacuum test as per video per link below (i don't really know what the gauges numbers mean):-

http://sendvid.com/poxkw3yy


Also checked fuel filter and found as per images attached (looks like i had water mixed up with fuel):-

Didn't do the fuel pressure test as i don't know where i have to connect the gauge. Would really appreciate your help.

Could it be a fuel problem (injectors) or plugs problem ???

all Dodge - sorry forgot to take note of the serial number

 

[alldodge]

You have a bunch of crud in the filter for sure. That can cause many issues.

Your idle vacuum shows smooth a steady, just 15 in Hg but steady