# Mercruiser 3.0 I/O wants to die upon acceleration.



## Georgiadawgs78 (Aug 29, 2017)

I've got a mercruiser 3.0 I/o in a pontoon that ran good up until about 4-5 weeks ago. It died out on the water with me and I found the problem to be a broke exhaust rocker arm and s bent intake push rod on the #2 cyclinder. 

So I ordered a new set of arms and rods and sent the head off to be gone through for precautionary reasons. They said everything was good, no bent valves or warped. 

So I put it back together and crank it out of the boat on a pallet and everything seemed to run fine. Throw it in the boat and put the ear muffs to it and it cranks and idles perfect but when you accelerate it either spit and sputters some or will run up to what ever RPMs and run a few seconds then just dies. I can back off of it some and play with the throttle and sometimes it will keep running and some times it sputters and dies. 

Anybody have a clue what might be wrong? As far as I know I got everything hooked back up correctly but there's a chance I got something wrong. I'm a little worried I may have the valves too tight but I adjusted them per the manual and they sounded good from what little experience I have.


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## Georgiadawgs78 (Aug 29, 2017)

I'd also be grateful for any contact info for a good mechanic in the NE Georgia area that may could get it running before this weekend.


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## transfixer (Aug 29, 2017)

Hard to diagnose something like that without hearing it in person, but it sounds like you are running out of fuel ? fuel line kinked or restricted ?


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## Georgiadawgs78 (Aug 29, 2017)

transfixer said:


> Hard to diagnose something like that without hearing it in person, but it sounds like you are running out of fuel ? fuel line kinked or restricted ?



I wouldn't think so but I'll check in the AM. The line from the pump to carb is pre formed metal and the line from tank to the pump is rubber. It's possible it could have got in a bind since I installed it back before we set the motor all the way down.


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## WayneB (Aug 29, 2017)

fuel pressure gauge on, it should have around 6-7 psi for a carburetor.
another issue may be ignition, you can try to troubleshoot with a timing light to see if it just dies when it sputters.
 I'd guess if it's sudden, a fuel filter or restricted line.


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## NE GA Pappy (Aug 29, 2017)

starving for fuel for some reason.


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## Lukikus2 (Aug 29, 2017)

The rubber hose could be calapsing from the inside restricting flow. Ethanol eats them up.


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## Georgiadawgs78 (Aug 30, 2017)

I didn't have time to work on it much but I confirmed the rubber hose was good. Previous owner ran non ethanol and that's all I've ran. I got the valve cover off so I'm going to back off the valves and then try and crank it without putting the cover back on and see if that may fix the issue as that's the only thing that changed really.


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## WayneB (Aug 30, 2017)

to remove head, you either removed carb or removed manifold with carb on it. Check the float and needle.


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## BornNRaised (Aug 30, 2017)

Sounds like the high flow jet in the carb is clogged, possible wrong jet, or float issue.

These are the things I'd be looking at.


 Runs fine at idle- soon as you gas it,  it's starved =carb


You could always double check fuel pump/filter and make sure to use FRESH fuel.


Many times it ends up being dead gas for alot of issues.


Hard to armchair diagnose.


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## Georgiadawgs78 (Aug 31, 2017)

WayneB said:


> to remove head, you either removed carb or removed manifold with carb on it. Check the float and needle.



I took manifold off with carb still attached and didn't mess with any of it. Don't know if that makes a difference but I'm going to work on checking out the carb next. They aren't really my forte. 

 I've ran 3-4 tanks out this year and put only non ethanol gas in it. Some from marina and some from store up the road. Both should be good gas being on or right next to the lake and getting used regular I would think.


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## WayneB (Aug 31, 2017)

I'm thinking the float arm wedged to one side and locked up while manifold was off the engine, just pop the top off carb and see if float arm moves freely. You may also find the fuel line inlet has a filter block inside, if you see where the line fitting goes into a much larger fitting on the carb, break the large one down and see if there's a filter hidden in there.


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## Georgiadawgs78 (Sep 1, 2017)

WayneB said:


> I'm thinking the float arm wedged to one side and locked up while manifold was off the engine, just pop the top off carb and see if float arm moves freely. You may also find the fuel line inlet has a filter block inside, if you see where the line fitting goes into a much larger fitting on the carb, break the large one down and see if there's a filter hidden in there.



I wound up letting another guy take the carb off and clean it but it looked good per him. Finally got the right parts for the carb and the fuel water separator so going to give that a try and see where we wind up.


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## 95g atl (Sep 2, 2017)

if you took the intake manifold off and didn't replace the gasket, could be a bad gasket, not tight bolts, etc.  Causing a LEAN condition when anything above idle speed.

also check timing.
water in fuel.
fuel filter and lines.
spark plug wires not attached or attached to wrong cylinders.

My bet is still on gasket and/or bolts not tight...since you did remove the intake manifold

Good luck


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## Georgiadawgs78 (Sep 4, 2017)

Well either rebuilding the carb or changing the fuel filter seemed to do the trick. Ran it the past two days and so far so good. Only issue now is, and it never did it while I was working on it at the shop or the first few times in the water, but when I go to cut it off it spits and sputters like it wants to try and keep running. It may do it for just a couple seconds or like 7-8 seconds. Seems kind of weird to me. 

Thanks for the suggestions and help!!!


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## Dialer (Dec 26, 2017)

Sounds like timing....


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## NE GA Pappy (Dec 26, 2017)

Dialer said:


> Sounds like timing....



prolly improper idle mixture adjustment and idle speed


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