3.0l Intermittent Sputtering

[Ciscovet]

Hey guys and thanks in advance for your replies.
I have a 2001 sea ray with a 3.0l mercruiser that i bought at the end of last year. Only recently has it started giving me some issues. The last two out of three times I have had some poor running and sputtering situations.
It starts up without any issues and idles a tad bit high. Now it will sputter/run rough and at full throttle will run at a lower rpm (4800). Feels like there is power loss too. The top end speed is lower as well (28-29 mph). After a while at full throttle the sputtering will go away and the engine will run fine (WOT 5200) and top speed ~34mph for the rest of the day. My thinking was that there was some gunk in the carb that got shot out because the following week the boat ran fine. But this last weekend it started to do the same thing and once again after some time at a higher rpm the boat ran fine.
Now I am really haven't done any engine work but I am not stupid either. I imagine I could probably troubleshoot this problem myself. Any case I want to start working on these things myself to save me some money. In any case I am looking at a couple of things. Probably needs a fuel filter (should have been done at the last marina but who knows), possibly a carb rebuild or sticking choke.
ANy idea?

 

[Oshkosh1]

Re: 3.0l Intermittent Sputtering

Start with the basics...

When was the last tune-up?

Check the plugs, look at the color, they can be a window into the inner workings of the engine. They'll tell you whether it's running lean/rich. Check the gap and overall condition.

Check the cap/wires(resistance should be no more than 14 ohms) also.

My thinking was that there was some gunk in the carb that got shot out because the following week the boat ran fine.

NEVER trust an engine(or any mechanical device) to fix itself...!

Someone here has in their signature(regarding troubleshooting) words to this effect:

"In marine engines, when your first instinct is fuel...check the ignition."

None of the above requires any real mechanical skill...just a little time, some basic tools, a gap gauge and a multimeter.

Good luck!

 

[fat fanny]

Re: 3.0l Intermittent Sputtering

I would suggest getting the merc service manual for your rig and read it cover to cover. If your running that thing at 5400 rpm for any length of time it will not be runnin for much longer max rpm is 4500 to4800 I believe. As mentioned above time for a full tune up plug,wires,cap&rotor,filters and fluids then go through all the electrical connections making sure there all tight and corrosion free then move onto the fuel cells vent to ensure there is no blockage and or debri in it's opening then make sure the anti siphon valve is operating properly. Good luck and post back.

 

[Calebt]

Re: 3.0l Intermittent Sputtering

I had this problem with mine also. went to the shop purchased points, plugs, wires,fuel filter, new cap and rotor set the timing and still had the problem. What fixed it for me was a fuel, water separating filter and some fuel stabilizer in the tank cleared things up for me.