3.0 Merc Stuttering

[blacklab75]

I have a Searay 1996 Merc 3 that is acting like its starving for fuel. It runs fine at idle but, when I accelarate past 2500 rpms it starts to bog and stutter.

I thought it was bad gas so I topped off the tank (10 gallons) and also put some stabilizer in it. Then, just to be sure I cleaned the carb with some spray and the also the flame arrestor. Went back out and it all seemed to be fine.

However, the next time I took the boat out it ran fine for about a half hour and the stuttering returned. I put some more fresh gas in (five gallons) and tested the boat out in the driveway with the muffs on. It ran fine.

So, I back to the water I go again and it starts stuttering. I also noticed that when it got choppy and the boat rocked the engine would sputter.

I 'm thinking it could be a bad fuel pump. Does it sound like this is whats causing my problems? If so, the current pump does not have a water seperater on it. Can I install a new pump with the water seperator on it as well?

 

[sltintexas]

Re: 3.0 Merc Stuttering

I am no expert but I went through something similar a month ago. I ended up rebuilding my carb and doing a tune up and everything is running great.

if you just sprayed carb cleaner into carb throat you didn't really clean much out. All the internals are what need to be cleaned and you have to rip it apart and clean those out by soaking them in carb cleaner and/or blowing them out with compressed air.

to test fuel pump you will need to get a pressure gauge on the output side of the pump. I'll let those smarter than me chime into what it should read.

From reading other posts others have mentioned loose connection causing the issues if you have it happen during rocking. Again, I'll let those smarter than me chime in with more details.

 

[cr2k]

Re: 3.0 Merc Stuttering

Stutters when it rocks? Huh? Well maybe your fuel tank has water in it and when the boat rocks it stirs up the water and it is sucked up to the carb. And/or your carb has water in it to. Do you have a fuel/water separator?

Pump some fuel from your fuel line in to a clear container and let it sit for 1/2 an hour and see if there is water in it.