Mercruiser 3.0 Engine Starved When Speeding Up Driving me nuts!!!!

[tommyboym7]

Hey guys, I'm new to this forum and new to boating as of last year but have an Issue driving me nuts with Bayliner 185 with Mercruiser 3.0 engine. Started late last season where boat starts and idles fine as well as revs up RPM fine while sitting. Then once in gear still runs fine but when pushing throttle while in gear to speed up it seems to starve the engine and sputter almost like i'm not getting enough fuel. It would then snap out of it after about 5 minutes of struggling while trying to get up to speed then run fine for the rest of the day. Then it started getting worse and wouldn't snap out of it. Now this year it's doing the same thing again and just struggles while in gear and trying to go faster than a few miles per hour and wants to cut out when giving gas while in gear but fine if in neutral and giving gas or just placing in drive and going very slowly.

Things i've done to try to fix: Additives (sea foam), drained gas and put fresh gas in (non-ethanol) (old gas been using in mower and runs fine), new plugs (several changes), new wires, new fuel filter, new distributor cap and rotar, cleaned carb, new carb fuel line filter, new carb float, new carb needle, checked fuel pickup screen and is clear. Not really sure where to go next with this maybe fuel pump replacement? Just seems like somethings blocking it from getting enough fuel or possibly an intake issue? Any ideas would be greatly appreciated!! All of these things have been done recently.

 

[vroom ZOOM]

to rule out the fuel pump I would recommend doing a fuel pressure test. Also have a look in the adults only section, there is a section in there on how to test your fuel system. Also a possibility is a sticky power valve.

 

[Scott Danforth]

welcome aboard

first, there is no "mechanic in a can" when you went thru the carb, did you chase each passage with a fine wire?

Second, did you clean the tank? fresh gas in a dirty tank means dirty fuel, as the ethanol in fuel is a great solvent to dissolve the crud that was dried in the tank prior.

what is your fuel pressure?

 

[starcentral]

This was happening to my 3.0 Mercruiser as well and drove me nuts but it was only really prominent when I used crappy gas and from then on only put ethanol free premium gas in my boat and the issue went away.

My switching of gas might have just been coincidence. Have you checked air vent on tank? Also try leaving the gas cap open and testing your issue, maybe you have tank pressure issue.

Curious to see what you end up finding.

 

[Middjack]

1984 Glastron Conroy with a 125 HP Mercruiser 3.o. I have a recently refurbished Mercruiser 3.0. It runs, but stalls and backfires despite having a recently rebuilt carb. At 1800 rpms it will stall out. You sometimes can get it past the 1800 rpms mark without stalling and it will run smoothly and operate at full speed. Does anyone know what might be causing the backfiring and stalling at 1800 RPMs?

 

[Rick Stephens]

1984 Glastron Conroy with a 125 HP Mercruiser 3.o. I have a recently refurbished Mercruiser 3.0. It runs, but stalls and backfires despite having a recently rebuilt carb. At 1800 rpms it will stall out. You sometimes can get it past the 1800 rpms mark without stalling and it will run smoothly and operate at full speed. Does anyone know what might be causing the backfiring and stalling at 1800 RPMs?

Start your own thread! Why hijack someone elses?

 

[tommyboym7]

Thanks for replies!! Some good points here, Vroomzoom i'll definitely look at fuel pressure check and sticky power valve. Scott good point, i'm still learning some of this stuff so didn't think of running a fine wire through it. We did check that carb cleaner was making its way through each passage but can definitely run the wire. Also didn't think about tank, had not seen any dirt or debris in gas I pulled out but i'll have to look at cleaning it. I have tried running it with gas cap open and no luck there, as well as have only been running non ethanol gas since i've had it which is only a year and half. Sounds like i've got a little homework here to test a few other things and see what may work, fingers crossed!!!!

I'll be messing with it again this weekend and hopefully one of these suggestions works!!! Will post the result.