mercruiser 3.0 backfiring and running bad

[cbucner]

Hello!
I have a 2000 searay with a 3.0 mercruiser engine.
I've been having problems and never got them fixed.
For starters The boat was running bad , backfiring when i first took it to the water, beeing the first time didn't know too much about these engines.
Anyway the head gasket was blown , I was lucky I could still get to the shore, the puffing noise was comming out of the engine bay.The gasket was shot at piston 1 .
Fixed that , read some more on the service manual , to find out that the timing was off.
got a digital timing light , and then replaced distributor cap, rotor, wires and sparkplugs , as well a new oil change , gas filter carb filters all the tune-up .
I did the timing , it was off , the boat was running like a champ.All good until I took it to the river and I hit some sand bank with the prop, then right away the engine started to backfire again and run like crap again.
It will Idle fine then when you want to take off it hesitates and starts to backfire .'
I checked the timing again, it was perfect.
Next time I took it out it was runing fine , I went few times up and down the river all good, then I stoped for some fishing.
After that I wanted to move to a new location , engine running like crap again.It drives me crazy!!!
Since then it's like that runs fine when cold and even when hot it reaches 190-210 degress since I changed the thermostat.But let's say I stop for 5 mins then runs like crap again.
Itook it out again and this time the alternator gave up this time.I'm at the end with this boat , I never enjoyed it.
I want to fix it because I love the boat but I'm running out of options.
Please help if you guys have any experience with same problems , or sugestions.
Thanks for any replies.

 

[Haut Medoc]

Re: mercruiser 3.0 backfiring and running bad

Welcome to iboats
It appears that you have multiple issues....
It sounds like a carb/fuel delivery issue with regard to the backfire.......
I would change the water separating fuel filter for starters.....
190 is too hot for that engine, i would check the impeller in the drive for signs of wear or overheating.....
I would also check the cylinders for signs of water intrusion, you may possibly have an leaky riser/exhaust manifold.......
Is this a raw water or fresh water cooled system?........
You will need the proper service manuals for the drive & engine....
So, stick around someone will have that info....
In the meantime if you have your seril #, post it up.....
It will let the forum know exactly what package you are trying to repair........JK

 

[ron7000]

Re: mercruiser 3.0 backfiring and running bad

I have a 2002 bayliner with the 3.0. It is a good engine provided you know engines and know how to maintain it. Otherwise It can be very tempermental and give you a headache real fast. In particular pay close attention to the fuel system, you need clean fuel otherwise it'll clog the carb and cause your backfiring and poor performance problems. Check the whole fuel system, all the way into the fuel tank if possible. Check and make sure there's no water or sediment in your tank, because it will make it to the carb and negate any fix you do. The 3.0 from what I hear does not come standard with a water separating fuel filter. Mine did not, had to add it myself. If you don't have one, you should add one. The little screen at the fuel pump and carburetor is not sufficient. Rebuilding the carb is pretty much common maintenance on this motor, if it hasn't been then you're due. Hopefully it's just a dirty carb that's causing your backfiring and hesitation problems, but a head gasket failure indicates something more serious.
head gaskets don't let go for no reason. If it was a 1970 motor with thousands of hours then not as big a deal, but a 2000 motor means you have a problem and you need to find what caused it to let go. At worst you have a warped head or cracked head. And a cause for that could be engine froze over the winter from having water in it. Other reason could be the manifold/riser is leaking water back into the cylinder and it can blow the head gasket on startup, however you mentioned the head gasket let go on #1 cylinder. #1is the front of the engine, the riser is at the rear so I would expect the gasket failure around #4 and #3 cylinder if the riser gasket was leaking. Or your manifold may have a crack in it, also from freezing, and it's leaking into #1. Just a few guesses to give you some places to look.
Also, it is the EST ignition/distributor, correct? are you disabling the advance on the distributor when checking/setting the timing? if not, then your timing is probably incorrect. Timing advanced too much can cause a head gasket to blow, but you should've had many tell tale signs of over-advanced timing: pinging, high operating temperature, white burned or disintegrated spark plugs, and engine runon when shutting off.

correct thermostat is a 160 deg F, a 140F will work also, and you don't want to go higher than 160. If your temp gauge is correct reading at ~ 200F then something's wrong. The only 2 things to really change are the thermostat on the engine, and the impeller in the outdrive. If you've never done the impeller in the drive, then you should. Hitting a sand bar, and if you run in shallow sandy areas, can deteriorate the rubber impeller rather quick.

what is your location?
did you do the work yourself, or have a mechanic or shop do it? When you or they pulled the head, what was the condition of the valves, and valvetrain? Backfiring is also caused by the valves not sealing, for various reasons. Was the head put back on properly and the lifters adjusted properly? Was a compression and/or leakdown done after the head gasket was replaced? I ask because if the valvetrain isn't 100%, then you'll never be able to tune the carb to get good performance.

 

[cbucner]

Re: mercruiser 3.0 backfiring and running bad

The timing was off that's why the head gasket blown.
It was backfiring and I still tried to get to the shore that what caused the gasket to blow.
I did the replacement , I did several engines before not boat engines but reg v6 and v8 engines , I'm not new to these things.
I used the specs in the mercruiser service manual to torque the bolts. everything was done by the book.
the engine it's like new , under 100h on it, the valves and everything else looks like new .
I added myself a water separation filter before i did the tuneup.
I did not check the impeller on the drive , that should be my first check next.
When I did the head gasket I checked the exhaust and the cylinders , they look like new , 160 psi compression on every single one of them.
The exhaust was kinda full of rust but i cleaned it perfect before I intalled it back.I used brand new gaskets and thread teflon for all screws that goes were holes have access to water such as engine block.
The engine runs perfect out of the water.
I run it on a water hose , runs like new, no backfire or anything all the way up to 4500 rpm.
In regards to the advance , yes I put the timing in base mode before I did the timing.
That's why it's driving me crazy!!!
I have to go and buy the drive service manual so I can start with the impeller.
Second I have a ping noise when the backfiring occurs like a sound when you have a electric leak on a coil or a spark if you know what I mean!
I'm thinking it's a missfire on one or more cylinders.
and third I have something like a ratlle noise comming from the back of the engine , like where the coupling in between the engine and the drive is.
It's not bad but when you run you hear it like tic -tic-tic
It's not a valve or lifter noise it's in the back of the engine , if you lift the drive higher the noise is lauder.
I'm thinking it's the U joint or something around there.
I've seen a grease fitting in there but is so hard to reach is under the bearing or whatever it's in there.
The carb I took it out cleaned it perfect, changed all the filters , did not do a rebuild though.
Here's a pic of the engine
http://64.65.22.75/boat/engine.jpg
When I got the boat there was no thermostat, It came from Florida, I installed one but like I said I'm around 190-210 degrees so I think it's the time for an impeller check.
Any other info will be much appreciated.
THanks

 

[cbucner]

Re: mercruiser 3.0 backfiring and running bad

I forgot , I'm in Wheaton IL 60187

 

[Haut Medoc]

Re: mercruiser 3.0 backfiring and running bad

The engine runs perfect out of the water.
I run it on a water hose , runs like new, no backfire or anything all the way up to 4500 rpm.
If it passes a compression test on all cylinders.....
There are not a lot of things that cause backfire....
This suggests a fuel delivery problem.....
Water in fuel, or lean mixture, clogged anti-siphon valve.....
The attitude that the boat sits while in the water may put sediment in the tank & clog the pick up screen....
You didn't say whether the backfire was only occurring under load or all of the time......
The engine isn't doing any work sitting on the trailer, so it is unlikely it would backfire anyway....
I would pulll the plugs & check for signs of water in the cylinders......
Are you positive that you have the wires in the correct firing order? 1-3-4-2?.......JK

 

[cbucner]

Re: mercruiser 3.0 backfiring and running bad

Wires are perfect , like I said the engine runs perfect out of the water, if the wires were bad it wouldn't run perfect.
It starting to backfire when I start to hamer it.
it runs fine until 2300-2500 rpm but then when it's time to get on plane and go above the 2300-2500 rpm starts acting.
Thanks

 

[cbucner]

Re: mercruiser 3.0 backfiring and running bad

Just a question??
What's the best pitch for this 3.0 engine on a 18 foot boat??
I have right now a 21 pitch which came with the boat and I think it's killing my engine.
Thanks

 

[cbucner]

Re: mercruiser 3.0 backfiring and running bad

And to change the water pickup impeller do I have to remove the bottom part of the drive??
Thanks!

 

[Haut Medoc]

Re: mercruiser 3.0 backfiring and running bad

Depends on the diameter & the configuration of your specific hull.....
Over propping is very bad for the engine & will cause all sorts of problems.....
That particular question would best be answered over in the prop forum.....
But I can say this....
You should be able to get 3900-4300 rpms under load, if the engine is properly tuned......
You need to figure out your other problems first, IMHO.......JK

 

[Haut Medoc]

Re: mercruiser 3.0 backfiring and running bad

!And to change the water pickup impeller do I have to remove the bottom part of the drive??
Thanks

Yes you do.......

 

[ziggy]

Re: mercruiser 3.0 backfiring and running bad

i don't know yer oem service manual. but my oem service manual for my 75 mercruiser has a recomended prop section. it's been real close on the two boats i've delt with.......

don't know about yer 3.0 with a 21 ontoit. i got a l6 and i'm doin a 19 on a 19' boat, vhull. gets me perfet wot. had me a 21 ontoit when i got it. couldn't get wot w/o trimin real high, too high......just my uneducated guess that yer pitched to much....... i have the same fear that you have. that i've already had damage to my engine for to much pitch. to much load. mine came that way from the 1st owner. even got two 21's when i got it. dought i'll ever use them again. less it be for a spare and i ain't even gonna do that. i'm gonna use a 17 for that...........at least with a less pitch i can controll when i'm gettin excessive with wot.........bein able to achicve wot is whats critical i think.

ya don't say what drive ya have. i assume a gen2. a 2000. got me a buddy with a gen2. he's gonna change the impeller this year. no overheat probs. yet. from what i read, gen2's have a better impeller life expectancy than the alph1s. still think yer on borrowed time. same with my buddy. read that mercruiser manual. it's got all the info in it for how to R&R that impeller. off the lower comes i think....

are ya fresh or raw water cooled? ya ain't said yet. 140* t-stat for raw water cooled, 160* for fresh water cooled. + 20* to full open i think. point is that it will vary within that 20* between open and closed. on the high side. but needs the correct one for whatever ya got. raw water cooled of fresh water cooled. another clue would be that yer previous owner had the t-stat out. would lead me to think that it was overheatin prior to you gettin it.....

guess i'd be sure ya are hip to timein. specially if yer hearin a tic tic tic whilest under load. ya don't want to be detonatein that baby........

thats my amature boat mech guess.....for a start.....like useuall. if i'm lame in my statements. please correct me, anyone. i'm just a boat mech wanna be......heck. i can't even fix my stupid toyota 4 banger on my 91 toy pu. but that's a different story.....i think...

if ya got a rattle. use a hearin hose to locate it. any ol hose. one end to yer ear, the other locatein the noise....

the way i look at engine diagnoisis is. it's a matter of findin out what works proper, and that ain't the problem. keep lookin till ya find something that don't meet that mercruiser service manual specifications and that may be the problem........good luck......ya'll find the issue in the end i bet. hang in there......patience is a vitue....

if yer manual is in two parts. best get the other half so ya got the facts. ya gots to know the facts before ya can do much diagnoisin or workin on it i'd think......

 

[Don S]

Re: mercruiser 3.0 backfiring and running bad

What is the serial number of your engine. Also, what did you set the timing at? After you set the timing and took it out of base timing, did you check to make sure the advance timing was actually working?
One of the biggest problems with the 3.0L engines (especially the new ones) is the carb is adjusted too lean. Did you try to richen the mixture, or just leave it as is?

 

[ron7000]

Re: mercruiser 3.0 backfiring and running bad

I see you used the same type gasket i used on the thermo housing. ultra copper ?
from your last descriptions, I would agree with don that you either need to tune your carb or clean it out entirely. On my 2002, i've had to do the carb 3 times, just the way it goes. With timing, after setting it to 2 deg *AFTER*TDC in base timing mode, undo the jumper and you should mark around 14 BTDC on the balancer with the timing light. From the manual I referenced for mine, forget which merc number, at 2600-2800 rpm you should get maximum advance of 26 +/-2 BTDC. check that and make sure you don't have some sort of malfunction with the distributor.

when you say cleaned the carb perfect, but did not do a rebuild, I don't know what you mean. My experience is that you need to pull the bowl cover off, clean all that old gasket material off which is the most time consuming p.i.t.a. part of the whole job. Then use a liberal amount of carb cleaner sprayed thru all the internals and preferably compressed air to blow everything out and dry. Being 6 yrs old I would replace the power valve if it hasn't already, if that's not working it'll lean out under throttle and backfire. Use your serial # off the carb flame arrestor and punch it in at mercurypartsexpress.com. You will probably need the more expensive pwr valve, the $20 one, you need to check the carb casting number to know which one of the two that are available. The carb is set to run lean thanks to emissions, I highly recommend upping your main jets from 1.55mm to 1.60 at least, preferably 1.65mm. That should fix any lean problem caused by the carb. The other thing to double check is your valve lash setting. It is 3/4 down from zero lash, I've experimented with that a lot on mine and found if you are less than that it will pop at wide open throttle. And you don't want to be more than 3/4 down of course or your valves will hang open and that'll definitely cause backfiring.

my boat is a 2002 bayliner, 19' model 1952cn, has a cuddy cabin. the drive is a 2.0 ratio and the boat came with a 21" pitch prop and mine screems at 4900-5000 rpm. You're a foot smaller so I would bet a 21" prop is not overpropped for you. You just need to get the motor tuned right and making power.

 

[ron7000]

Re: mercruiser 3.0 backfiring and running bad

i have the same fear that you have. that i've already had damage to my engine for to much pitch. to much load. ..bein able to achicve wot is whats critical i think.

the "your overpropped" mentally is blown way out of proportion on this forum. You're not going to do any damage to the motor if it's tuned fairly well and the boat gets on plane. Overpropped would be having to get everyone to the front of the boat everytime to get on plane, only reaching 3000 rpm, and watching your water temp gauge rise. Hitting 4000 rpm opposed to the "recommended" 4600-4800 rpm is not overpropped. Biggest problem is people don't have their motor running 100% and it doesn't make it to the recommended rpm range because it isn't making full power. For example it may only make it to 4000 rpm for the given prop pitch, then they conclude they are overpropped and go down in pitch to achieve higher rpm instead of fixing the real problem. Next thing you know, everyone's running 15" props and anyone running a 21" pitch or larger is automatically overpropped (joking). It all depends on the outdrive gear ratio, small boats with the 3.0L have a 2:1 gear ratio and run a 19-21" prop. The 6 cylinder engines may or may not run a lower gear ratio, 1.6:1 or 1.8:1 and the prop pitch may or may not change. So you have to factor in the boat hull and weight, and also be sure the motor is 100% and most of the time it isn't.

 

[cbucner]

Re: mercruiser 3.0 backfiring and running bad

I started today by draining the drive oil out.
It's kinda cold here around 35 today and it took forever to drain out.
I have the level monitor for the drive inside the engine bay in top of the alternator and drain that one too, it had some thick oil on the bottom looking more like grease already.I cleaned the container drained everything out and tomorrow I'll remove the botom part of the drive to check my impeller.
I want to take it easy and eliminate every problem that can be one by one.
I'll let you know guys tomorrow what's goin on in there .
I'll take some pics of the engine ser nr and drive ser nr , I think I saw that the ratio is 2.00 on my drive and ser nr of the drive is 0L731625 and transom is 0L832816
I'll pick up the engine one tomorrow.
Thank you guys !!
Can't wait to see what's going on on the impeller area tomorrow.
I'll keep you posted.
THanks again.

 

[cbucner]

Re: mercruiser 3.0 backfiring and running bad

What is that power valve doing on the carb??
Is there any way on checking it??
THanks
I guess is the one with the purple wire, right??

 

[aerwin]

Re: mercruiser 3.0 backfiring and running bad

Wires are perfect , like I said the engine runs perfect out of the water, if the wires were bad it wouldn't run perfect.
It starting to backfire when I start to hamer it.
it runs fine until 2300-2500 rpm but then when it's time to get on plane and go above the 2300-2500 rpm starts acting.
Thanks

 

[aerwin]

Re: mercruiser 3.0 backfiring and running bad

Wires are perfect , like I said the engine runs perfect out of the water, if the wires were bad it wouldn't run perfect.
It starting to backfire when I start to hamer it.
it runs fine until 2300-2500 rpm but then when it's time to get on plane and go above the 2300-2500 rpm starts acting.
Thanks

oops, sounds like the advance in the distributer isint working properly. or the attitude of the boat causes a fuel delivery problem

 

[Don S]

Re: mercruiser 3.0 backfiring and running bad

What is that power valve doing on the carb??
Is there any way on checking it??
THanks
I guess is the one with the purple wire, right??

STOP working on that engine until you have the Mercruiser Service Manual #26 for your engine. You obviously don't have a clue what a power valve is or does, let alone where it's located. That thing on the carb with the purple wire is called an automatic choke.

You also have a 1999 engine and drive on your SeaRay 180BR and your engine serial number is 0L638511.

Have you tried adjusting the idle mixture on the carb. Sounds like it's way too lean. Probably because of the stop on the adjustment.
Gotta' find the fairy tale post so you can read it.