Engine Stutter - 2000 RPM - 1992 Moomba Supra

Today after many weeks of flawless motor operation, when I was taking the boat up to the normal 3000 RPM for the spin around the lake, I noticed that at 2000 RPM the speed wasn't increasing. When I pushed the throttle further, there was a stutter or chopping noise coming from the motor. So I backed off and tried it a again, and got the same result.

So I let the motor rest of a couple hours and went back out. This time I ran the motor at 2000 RPM for 10 to 15 minutes before increasing the throttle. Got the same feedback. Anything over 2100 RPM, the motor was chattering, almost sound like it was missing.

Any ideas?

Thanks,

dbloom

Start with popping your distributor cap and looking for corrosion. When was the last time the boat had plugs, cap, rotor, etc. done?

Thanks. Doesn't have distributor cap. Was changed over to electronic ignition. Would a fuel filter be a possible culprit? or a dirty carburetor? It's just weird that when it idles, it sounds perfect. All the way up to 2000 rpm, engine is smooth. About 2300 rpm, it stutters. So I revved the engine on the lake the other day without the powertrain engaged. Same issue...

hmmmmm...

Thanks,

Uh, unless you are running a new LS platform or something with coil packs it would still have distributor cap. If not, I'm super curious what you're running as I might want to upgrade!

It wouldn't necessarily have points and condenser or an external coil any more like old school stuff, but would still have a cap and rotor at a minimum.

My first thought is ignition as well, but if it’s not it could be the secondaries in the carburetor aren’t opening (if the carb has vacuum secondaries).

it doesn't have the traditional coil and cap setup .. someone replaced it with a individual coil set up for each plug.. have not pulled it apart to see if there was a bad connection / corrosion issue as of yet...

I did pick up some Sea Foam motor treatment and a fresh 4 gallons of fuel. Dumped both of them in the tank, took her out for a spin, and no more stuttering issues. A buddy of mine was telling me that he'd had the same issue and it was the carburetor. So before I attempted to tear it down and clean it (haven't a clue how to do this), I asked my local NAPA guy what he thought. He recommended the Sea Foam.

Will see how long this lasts. Hopefully for a while ...

Could have water in the fuel.

Quote:

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Originally Posted by dbloom

it doesn't have the traditional coil and cap setup .. someone replaced it with a individual coil set up for each plug..

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This I still want to see.

Ok I will take a pic and sent it. I pulled the coil connectors and everything is good and clean. Pulled the carburator with hope this was the issue, but after paying $350 to have it fixed (it was broken and full of gunk too), this still isn't the problem. The next thing is the plugs? God knows how long they have been in that engine. Lately I have notice a gas smell after the engine warms up for 10 minutes or when I bring it back in from cruising...

Now I get the statement that boats are money pits, but I am enjoying learning all this stuff too ..

Thanks,


DB

Good news! Life is good and the motor is running at 4600 RPM. How? Get the carburetor fixed and put in new plugs!! DuHH!!

Yes, the carburetor was broken in a couple places. Secondary butterflies were not opening; power valve was broken; diaphragm for excelator valve was the wrong size.

Pretty sure the gas wasn't the issue.

She is running awesome now. Just need to figure out where the water is coming from ... do these boats normal leak a little water ??

Thanks,

DB