yamaha 25hp 2stroke HELP???

avonmark15 · 07 May 2015, 19:30

We were out on boat today and we were going along and we heard a little tap so turned engine off we then started it again (took longer than usual) we got back and the power had dropped any ideas?? both spark plugs are dry etc now there doesnt seem to be a tap

RIB-Teccie · 07 May 2015, 19:51

Not enough info I'm afraid. When you say a tap, do you mean a knock?

avonmark15 · 07 May 2015, 19:57

yes a knock and underpowered seemed to get us back ok no funny noises after we restarted it and no lumpy running seemed smooth just under powered. we think it may be running on one cylinder

RIB-Teccie · 07 May 2015, 20:19

Just not enough info.

Check plugs for spark
Are you running 1:100 oil, an overheating piston could knock
Run compression test.
Ensure fuel and filtration clean
Check fuel pump
Check gearbox oil for metal. A failing gearbox can knock.

RIB-Teccie · 08 May 2015, 03:07

A single knock and then power loss. Outside chance of a flywheel key shearing. My guess is you limped home?