Boat slows down but Engine continues to run

[whytes]

I left my wife and kids with the boat at the lake while I went back to work. She called today to say she was going about 35 mph and all of a sudden the boat stopped as if she had quickly pulled the throttle back to neutral. The engine slowed down as if she had quickly pulled the throttle back to neutral. The engine sounded fine. The throttle was in the same position (forward). She moved it back to neutral and put it back in gear and off she went. This happened two more times at speeds between 25 and 30 mph. AFter the third time, she dropped some people off and shut off the boat. Restarted fine and then ran ok. Temperature, oil pressure all ok. She wasn't running aground if that's what you're thinking. It's a deep lake. The engine didn't over rev or run rough or anything odd when it lost power. It just slowed down just like the boat.

Any idea's? This has me baffled. Thanks.

Bayliner 1850 Capri - 4.3 l mercruiser.

 

[Don S]

Re: Boat slows down but Engine continues to run

Sounds like it was running out of fuel for some reason. Try this test.

http://forums.iboats.com/showthread.php?t=167561

 

[whytes]

Re: Boat slows down but Engine continues to run

Thanks Don. She's planning on driving it and taking her chances about getting a tow. Wanted to get some assurance that she won't do any serious damage or that some serious damage has already been done.

 

[whytes]

Re: Boat slows down but Engine continues to run

Wife is back. Have taken boat out several times so I could see the problem. Was fine until yesterday. Here's all the info I have gathered. Any help would be appreciated.

1) Problem originated after baby pulled the kill switch.
2) On occasion, the ignition does absolutely nothing. No click, no beeps, just dead - as if the battery were completely disconnected. I have found that by hitting the trim button, power returns immediately and boat starts without a problem (this has happened 4 times in about 30 to 40 starts). Also note that when the boat is 'dead' the radio is also dead. The only electrical button I have tried was the trim button during this situation.
3) When boat slows or chugs, the engine also slows, it has never stalled. The depth finder goes blank and alarms and the tach pegs out at high end. They immediately return to normal once throttle is pulled back.
4) Boat 'chugs' (actually I believe it goes between a neutral speed and the speed relative to the throttle position) when accelerating very fast.
5) Boat has never stalled. It always runs fine after an incident.

Is there something electrical that would cause the boat to slow - the throttle is via a mechanical cable? It just seems odd that we have all these issues that seem to originate around the throttle area.

Thanks.

 

[tarheelebbtide]

Re: Boat slows down but Engine continues to run

It definitely sounds like an electrical issue of some sort.

 

[AltheaToldMe]

Re: Boat slows down but Engine continues to run

I suggest looking for a loss of ground to the battery.

$0.02.

 

[chiefalen]

Re: Boat slows down but Engine continues to run

Take off and clean all the connections.The grounds also. I can't impress enough the ground issue. I would start with the battery connection, and leave off the the cable till all the other ones are clean. Than after all are clean shoot corrosion pro or some other can grease on the connections. Then reconnect the battery.

That kill switch could be popping in and out. You could for now bypass it. Easy enough to do. It's there to tie to the driver and if the driver falls overboard would kill the motor so the driver and get back in the boat.

I would clean all the filters. Never hurts, and could help.

Good luck !

 

[whytes]

Re: Boat slows down but Engine continues to run

Including all the grounds to all the instruments?

Thanks for the suggestions.

 

[hazwild]

Re: Boat slows down but Engine continues to run

I had the same kind of problem last summer.It was a ground issue. I cleaned them all including all sensor and gage connections. That fixxed it.

 

[Fishermark]

Re: Boat slows down but Engine continues to run

While cleaning - make sure the main engine plug for the wiring harness is in good shape without any corrosion at the terminals. Some dielectric grease wouldn't be a bad idea as well. Also - is the main plug clamped down? Instead of just plugging it in, add a hose clamp to it as well.