Problem with older 75 HP carburated Honda 4 stroke. Please help!

I have a older 75 HP Honda 4 stroke tht is on the back of a 2' AquaPatio Pontoon. Motor has been flawless for many years. Did have to change the impeller last year. Brother had it out over the weekend and ran aground on a hidden sand bar. Said motor did overheat but he did get unstuck. Said everything fine for 2 days. This morning called to tell me would only run at WOT for a few minutes before starting to sputter and die. Would start again and do the same thing. Did take cover off and noticed oil was the color of sand. He has checked the fuel tank vent and said it was partially clogged. Will check crankcase vent and change fuel filter. Also will check oil level. Anything else should we look for? Thanks for your help!

Yes....look for a new brother.....lol!

When it sputters and dies....is it overheating at the time?

Go ahead and check all that you listed....sand colored oil? Interesting. How deep in the sand did it go?

Pull the thermostat and see how much sand may be impacted there.

It is very possible that the sand has worn down the impeller and scored the impeller plate.

Mike

He's a good guy and alcohol may have been involved. When said sand colored I'm sure he meant water not sand was in it Just don't know how much. He will check oil level. He said not overheating. No overtemp light or buzzer and starts and runs to WOT right after it dies. Will check thermostat. Still is flowing out the pisser well. Will check compression as well. May be two separate issues. Thanks.

Don't just CHECK the oil!! CHANGE IT! If it is "discolored" or contaminated in any way, it makes no sense to continue running it that way unless you want more damage than has already been incurred. After reading that he ran it to the point of overheat, my opinion is that he may have cooked out the oil and has ALREADY caused some bearing damage. That's why it only wants to run WOT. If there is a lot of internal friction in the engine from scored bearings, cylinder walls and valve train components, then it will not "want" to idle.

These can be repaired after going through something like this but without careful assessment and handling, you could have a pile of scrap instead of an outboard real soon.

jgmo said:

Don't just CHECK the oil!! CHANGE IT! If it is "discolored" or contaminated in any way, it makes no sense to continue running it that way unless you want more damage than has already been incurred. After reading that he ran it to the point of overheat, my opinion is that he may have cooked out the oil and has ALREADY caused some bearing damage. That's why it only wants to run WOT. If there is a lot of internal friction in the engine from scored bearings, cylinder walls and valve train components, then it will not "want" to idle.

These can be repaired after going through something like this but without careful assessment and handling, you could have a pile of scrap instead of an outboard real soon.

Click to expand...

I am the mechanic of the family. He is not running it at all. Just my eyes from afar. Sorry for any confusion. Will idle fine. Anything over idle will eventually cause the motor to stumble and stall after a few minutes. The oil will certainly be changed before taking it out again. Was just asking him to check it to see if it looks over filled (maybe from head gasket) or just discolored from condensation.