97 bf75a Honda

[Bassgod]

I have a guy wanting me to look at his 97 Honda 75HP and I don't have much experience diagnosing them. He says his engine starts fine but will have a intermittent cough when its cold. Then once warmed up, it will run fine for 20 minutes or so and then cough once in a while when it is warmed up. He says the coughing is random throughout the rpm ranges? Any suggestions for good starting points in troubleshooting? Could it be a bad plug, or a coil?
Thanks.

 

[Bassgod]

Re: 97 bf75a Honda

Bump

 

[hondon]

Re: 97 bf75a Honda

Start with general diagnostics just like ahything else.For the compression test you will need to defeat the neutral safety switch to accomplish WOT.A fuel sample is a must to check fuel quality and for any water intrusion.Are those valves properly adjusted?Remember that as valves wear in they get tighter and can cause the lean snort you describe.

 

[Bassgod]

Re: 97 bf75a Honda

Thank you Hondon.

 

[JUSTINTIME]

Re: 97 bf75a Honda

coughing means running lean
go through the carbs

 

[hondon]

Re: 97 bf75a Honda

Alot of things can make these engines run lean. If you have the ability to water test this unit plug it in to a shop tank that you know works to isolate any fuel delivery isssues from the boat.Fuel quality is an issue everywhere and I have service bulletins from every manufacture that I represent.Merc is a good source for that info.An easy test that is cheap to do and I have seen some marina fuel that fails miserably.You may well have carb work in the future and likley do,but cover all the bases first.I hate scrapping that mani gasket.