Merc 25HP (1985?) stumbling - starts when cold, dies in 10 mins

[iehmove]

Our rowing club has a coach's launch that has been in use for 20 years. It is a small Smokercraft boat with a 25hp Mercury outboard, with remote electric start. Last year the boat ran roughly and was repaired, which included a new battery, tune-up and new fuel diaphragm. It ran well for two months this season and is now failing -- three weeks ago it stalled after running for 10-20 minutes, re-started and finished running for another 30 minutes. On subesequent outings it has been able to start cold and run for 10 minutes or so, then dies. It will not re-start afterwards, unless it has been sitting long enough (hours) to cool down. <br /><br /> <br /><br />We have the vent valve open and clear on the fuel tank, a correct fuel-mix, etc. Any ideas?<br /><br />Many thanks for your help.<br /><br />Chicago River Rowing Club

 

[ronmold]

Re: Merc 25HP (1985?) stumbling - starts when cold, dies in 10 mins

switchbox failure! When it dies spray the switchbox with component freeze-mist spray from radio shack to cool it down, if it starts again replace the switchbox. I have found the CDI/Rapair units work great.

 

[KIGuy52]

Re: Merc 25HP (1985?) stumbling - starts when cold, dies in 10 mins

Just curious...is that boat a Sea King Smokercraft?

 

[yeoman1]

Re: Merc 25HP (1985?) stumbling - starts when cold, dies in 10 mins

Sounds like it may be an engine in the final throws of life. Check the compression, may be time for a rebuild. If you don't have a compression guage, pour a small amount of Marvel's Mystery Oil in each bore when she won't start, then try her. The oil will seal the space between the rings and the cylinder wall giving her the compression needed to fire if that is your problem. The oil won't hurt a thing.