Boat running like crap after warmed up

Hello all & Special Request Out to Boat Dr:

First some background. Have owned 1985 Ski Nautique for approx. 10 years. Put on a prestolite electronic ignition about 2 - 3 years after I purchased boat (making elec. ignition 7-8 years old). I don't put alot of hours on the boat (boat has approx 775 hours total hrs). After this years Ice Breaker, I found out that the boat was experiencing some hesitation when throttling up with skier. Suggestion was made that I probably needed to have the carb. rebuilt (my previous mechanic just passed away and he mentioned at the end of the season that it maybe about time). I jumped to it and had an elder mechanic and boater rebuild the carb. At that time, I replaced the water / fuel sep. (a fram canister). Took a short period to get her up and running. Put she did fire up without to much trouble.

Problem is that after she's warmed up, she runs like crap. Rough idle, rough in gear, and hesitation when you push the throttle. If you're attempting to tow skiier, it may stall. Suggestion plugs, cap, rotor, and wires. DONE. Still problems continue. I don't mind spending a little money on her - (Don't get me wrong). I just would like some help doing it systematically and to test things when possible so that I'm not just throwing money at her. I wonder if anyone has some suggestions. My other questions - could it be elec. ignition, coil, or the carb (even though she's been re-built. "re" being part of that key word). It seems to run fairly nice cold (or should I say cool). But after warm-up almost seems to miss, stall, rough idle, hesitation, etc. You can give me a call (440) 915-5900.

Thanks, Matthew Brej (Cleveland, OH - WSWSC)

Have not checked choke plate. Thanks.

I had similar issues with my carb after a rebuild. Check and see if fuel is dripping from the primary venturi's at idle after warm-up. You shouldn't see anything. I had all of your symptoms, sometimes at the sametime, sometimes different ones intermitently. Mine varied so much because the amount of fuel leaking from the venturi's varied substantially from none, to almost enough to flood the engine at idle.

I think you have more than enough info to start here.. choke setting and operation is logical as that is the one thing that is supposed to change on your carb between running cold and running hot.. if nothing changes running once warmed up would certainly be a problem. Float setting or gunk on the needle and seat next best bet as dumping fuel gets worse as the boat runs longer and warms up as well.. and Chris is logical when he says you touched the carb and now it don't work so it is probably the carb.. start there and don't leave there easily...

Able to get back to the boat. Installed washers and lock washer and tightened carb, spacer to intake. When rebuilt, appears gentleman installed two new gaskets put carb wasn't down tight. Ran her and here are the results: Started on first turn. A little out of gear throttle a after start-up to warm her up. Put in neutral idle fine. Backed out of dock. Idled down canal (few minute journey - five minutes or less). At open water, I gave her a little - no problem. Up to around 35 mph and no problems. Back down to check acceleration - no problems nice acceleration. (tested several more times - same result). Good and warm when I came to no wake zone. Idle speed - at first, no problems. Then began to run rough. Turned around - out of no wake zone gave it some gas and about to stall. Let up (didn't stall-out) and gave it a little more gradual. Up to speed no problem. Slowed to idle and hit it again - no problems. Several attempts like this no problem.

Get back to marina channel to idle in and runs rough again. Seems like I lose rpms at in gear idle of 450 - 500 after warm-up. And it goes up about 50 rpm when I take her out of gear.

Any Ideas!!! I'm not great with carbs and don't want to mess it up more that now. Thanks.

Matthew Brej - (WSWSC - Cleveland, OH.)

You are supposed lose rpm's at in-gear idle vs neutral idle due to loading. Sounds like you need to adjust your idle mixture screws at in-gear idle after you get it warmed up. This process has been detailed several times on the site. Increasing your curb idle a tad will help keep it from trying to stall. I keep mine at about 600-650rpm neutral idle, 500+ in-gear idle. But if your idle mixture screws aren't set properly, it will still run rough. Typically 1.5-2 turns out on the idle mixture screws has been right for me.

Matt-


Post a picture of your boat. I wonder if it is one I used to ski behind here.

Tim