Strange engine starting problem.

[TeamPCBeach]

1999 Doral 300 with twin Merc 5.7 Bravo 3 and Kohler 6kw generator. If we run the generator for a couple of hours the engine compartment gets hot and the STBD engine will not start. Turn the key and get nothing. Engine acts like the throttle is not in neutral. PORT engine starts fine. Turn the generator off, let the blower run for 30 minutes and then the STBD fires right up.

So my questions are

1) Any idea what is causing the STBD not to start due to temperature in the compartment?

2) Should the generator running make the compartment so hot? I don't know what temperature the compartment is getting too, but the fresh water tank heats up so much that I bet the COLD water from the sink is 130-140 degrees.

Thanks in advance.

 

[WhySoSearious?]

Re: Strange engine starting problem.

I would start with the easy stuff -- swap the batteries.

since your starter isn't cranking, check for loose electrical connections or bad batteries.

 

[BSAFlash]

Re: Strange engine starting problem.

I agree with Whysoserious regarding the battery, it is highly unlikely that the starter solenoid would be heated enough to be effected.
The temperatures you allude to in the engine bay are extreme! I can run my generator for hours with no impact on my fresh water tanks, 60Deg C (converting your measurement to English) is more likely an issue with your mixer at the sink allowing hot water to come through with your cold water when you have the tap turned on to cold.

 

[TeamPCBeach]

Re: Strange engine starting problem.

Nope, not the battery. As soon as I let the engine compartment cool down by leaving the generator off for 30 minutes the engine will start. The fresh water temp is HOT. I get the same hot water from the cockpit sink that is only plumbed to the cold water tank. I am thinking it might be the generator water pump impeller. The generator runs fine at anchor, but once I get underway it dies. This coupled with the hot temp is leading me to a bad impeller that can't suck enough water.

Still strange as to what will not let the engine start when the compartment is hot.

 

[BSAFlash]

Re: Strange engine starting problem.

Assuming the layout is the same as the Elegante, the generator exhaust runs across the back of the starboard engine before exiting via a through hull fitting set just above the water line. The fresh water pipes run across the bulkhead, heating of these pipes will result in hot water until enough cool water has passed through to cool the pipe.
Check the cooling system on the generator as you suggest and the heatsheild on the generator exhaust.

 

[TeamPCBeach]

Re: Strange engine starting problem.

That is what I thought was happening, but we used the transom shower and ran several gallons of water out, still hot. I checked the generator impeller yesterday and it was good. The sea strainer did have a lot of silt on the screen so that could have been the cause. It is really strange since the generator does not over heat. Next time we go out I am going to check to see if there is an exhaust air leak anyplace. I also checked the bilge blowers yesterday and both are running and I didn't notice any kinks in the ducting.

 

[WhySoSearious?]

Re: Strange engine starting problem.

i can't imagine the engine bay getting so hot your fresh water tank heats up. can you use a thermometer and see how hot things are in the bay? and you don't have the hot water heater turned on? (no switched lines?)

i've read electronic connections can weaken in hot conditions so make sure your connections/terminals are ok.

i would still swap batteries and see if the problem swaps too. and then swap ignition switches or whatever. trace the current to the starter etc to see if there's a break somewhere.

 

[Lyle29464]

Re: Strange engine starting problem.

I would get a test light and see where you are missing the voltage when it will not turn over.

 

[BSAFlash]

Re: Strange engine starting problem.

Any luck finding the problem TeamPCBeach?
I am still at a loss as to how your water tank heats up, if the same as the Elegante (I think most are) the freshwater tank/tanks are on the other side of the bulkhead and insulated from the heat of the engine bay.
I agree with Lyle29464, use a test light or multimeter to trace the engine start issue, no doubt it will be a simple thing that will only cost a lot if you pay others to find it