Throttle problem 36c

[pathat315]

I am the proud new owner of a 75 36c Hatt. Brought the boat around from Traverse City/Lake Michigan to Lake Erie recently after the purchase. Boat ran perfect except a minor problem. The boat was repowered with new 502 marine power gas engines in 1996. They currently have 350 hours on the meters. Having a problem with occasional throttle up on a hot engine. Pulled into the marina a couple of times on the way down for fuel and lunch. Pulled back out of the marina after sitting for a couple of hours. Boat jumps up on plane then starts to sputter/loss of power at about 3k on the tach. Throttle back to idle then throttle back up and the engine then runs fine. It's and intermittent problem and only happens on a hot engine never when cold. Its also happened once after anchoring out for a couple of hours, then throttling back up for the marina. Only happening on the port engine. I was thinking possibly a vapor lock in the carb. Plugs, wires, distributor look good. Also changed the fuel/water separators. Only happens on throttle up, never while at running cruising speed. I am new to the forum and enjoy reading the posts. Sold a 83 31ft searay for the Hatt. Can't believe the difference in the ride. Most important, the admiral is really impressed. A couple of days were prettly rough on the way down Lake Huron. We would have never left the dock in the searay. No problem with the Hatt. Thanks for any advice/input.

 

[sofarelli]

We had a similar problem on a Trojan and it turned out to be a loose connection in the harness. Just an idea, it may be worth a look.
Mike

 

[jim rosenthal]

This doesn't sound like a problem that is peculiar to a 36 Hatteras, frankly. It sounds like a fuel starvation or ignition problem; on a hot engine it may be vapor in the fuel lines or something like that. If your engines are EFI or if they have electric fuel pumps you might try cycling the ignition on and off a few times before you start the engine. You could also have a problem with fuel boiling or evaporating from the float chamber in the affected carburetor, if you have carbs. Another trick you might try is to open the engine room hatches before you start the boat back up and see if cooling things down helps. Because of the insulation and thick hatches, a great deal of waste heat gets trapped in the engine room after shutdown and cooks everything in there, including the fuel already in the motor. I rigged a large 110v blower in my engine room on a timer, which runs for an hour after the boat is shut down. It moves a lot of heat out of that area. I don't know if this is possible with gas engines, as those blowers are not ignition protected, but opening the hatches for a while may help.
I assume you've checked the throttle cable linkages and they are not binding etc etc Good luck with all this.

 

[MikeP]

It's a a long shot but check the ignition coil. Oil-filled (conventional) coils are famous for weird, intermmitent, hard to figure out ignition problems. They almost always occur when hot with no symptoms when cold. I worked on a car years ago that would cut out when turning aggressively left. It was fine going straight or turning right. The movement of the oil in a hard left turn caused a faulty winding to short out. It worked fine going straight or turning right. New coil eliminated the problem.

It could also be an improperly set float level in the carb. If the setting is too low, there might not be sufficient fuel to keep the main jet supplied as the boat "squats" on acceleration. Once it's up on plane, the problem would go away. But I would expect it to exhibit the same behaviour every time. It wouldn't clear up after reducing the throttle setting and then increasing it again. But again, worth checking.

 

[garyd]

I agree with the coil thought line. Plus the quickest way to eliminate fuel related questions is to plumb a seperate fuel source directly to the carb or EFI. It will need to gravity feed so it has to be above the carb.