Runs fine for an hour or so then the problems start.

[oil can]

so i am a boating junky and love working on them. i have been trying to help my neibor with his 1988 21 ft sea ray. it has a 4.3 and i belive alpha one. the problem is when he goes out everything works well boating is good and then a half our or more in to the trip the boat starts to have running problems.... it looses power hesitates coughs then eventualy it dies. from what he tells me if he just lets it sit for a while he can fire it up and carry on his marry way. what im wondering is may there be something in the engine compartment that is electrical that is getting hot that would cause this? the motor its self runs cool no temp problems there. the whole deal just seems odd and i love a chalenge.

what are your thoughts?

ohh and thanks in advance.

 

[Lyle29464]

Re: Runs fine for an hour or so then the problems start.

An electrical component can do that. I have had a rotor do it. pop the cap. put ice on it for 30 seconds and its started right up.

fuel vent plugged can do that. Just open gas cap. May need to take a meter with you. see where you lose the voltage.

 

[ktbarrentine]

Re: Runs fine for an hour or so then the problems start.

Let's start on page 1C-5....

http://boatinfo.no/lib/mercruiser/manuals/mercruiser7.html#/40

 

[oil can]

Re: Runs fine for an hour or so then the problems start.

An electrical component can do that. I have had a rotor do it. pop the cap. put ice on it for 30 seconds and its started right up.

fuel vent plugged can do that. Just open gas cap. May need to take a meter with you. see where you lose the voltage.

i told him i would go out on the boat with him and i was going to take my volt meter and check a few things. the gas cap is an easy one one and could be a good easy place to start definitly.... so far i have just been going off of the things he has told me that he has tried..
thanks for the replie.

 

[oil can]

Re: Runs fine for an hour or so then the problems start.

Let's start on page 1C-5....

http://boatinfo.no/lib/mercruiser/manuals/mercruiser7.html#/40

I saw this manualy in a thread search i did. it is kinda hard to read beings everthing is so small.... could you give me an idea what is on that 1c-5 page so i can get closer?

 

[oil can]

Re: Runs fine for an hour or so then the problems start.

ok so i went back in to that manual and finaly found the zoom feature. i looked threw it again and the section you mentioned was the two barrel carb section. the one he has is the four barrel rochester... but from what i gather you think its a carb deal. but why cold start great and run fine for an hour or so? whats changing in the carb... i guess im not following where you are going with that?

 

[ktbarrentine]

Re: Runs fine for an hour or so then the problems start.

I saw this manualy in a thread search i did. it is kinda hard to read beings everthing is so small.... could you give me an idea what is on that 1c-5 page so i can get closer?

Use the "plus" sign at the bottom of the screen (towards the left) to zoom in. Works great. There is too much info there to transcribe. A wealth of knowledge. The "arrows" take you forward and backward in the pages, and there is a search feature at the bottom right side of the screen.

 

[ktbarrentine]

Re: Runs fine for an hour or so then the problems start.

The manual covers all the 4.3s of that year.... It is a troubleshooting guide. I cant say whether it is a carb deal or not... I recommend getting familiar with what the troubleshooting guide has in it and then try and narrow it down by the symptoms. Others can/will tell you what has worked for them, but your symptoms are yours... Best of luck!
(for example... I had similar symptoms awhile back...turns out the diaphragm in my fuel pump was cracked and was putting extra fuel into the carb via the sight-flow tube. Caused the engine to flood after running for awhile and would make it hard to start after it was warm.... so, you might see if there is fuel in the sight flow tube when the engine is running). KTB

 

[oil can]

Re: Runs fine for an hour or so then the problems start.

The manual covers all the 4.3s of that year.... It is a troubleshooting guide. I cant say whether it is a carb deal or not... I recommend getting familiar with what the troubleshooting guide has in it and then try and narrow it down by the symptoms. Others can/will tell you what has worked for them, but your symptoms are yours... Best of luck!
(for example... I had similar symptoms awhile back...turns out the diaphragm in my fuel pump was cracked and was putting extra fuel into the carb via the sight-flow tube. Caused the engine to flood after running for awhile and would make it hard to start after it was warm.... so, you might see if there is fuel in the sight flow tube when the engine is running). KTB

yah little stuff like that is what i want to keep my eye open for. thanks for sharing your problem and fix.

 

[oil can]

Re: Runs fine for an hour or so then the problems start.

a nother thing i was thinking about last night was what looks to be a oil presure switch on the back of the motor on the battery side.. the goofy thing is its wired i series in the line of the wire that turns the alternator on.... seem odd i will be checking in to that more.....:facepalm: