Misfire when warm

[Firemandave]

I have a ‘92 PCM 351 in my Ski Nautique. After running at 3200 rpm for about 10 min it backfires and looses power. Will start right back up abut noe sounds like it is missing. Any suggestions?

 

[makomark]

backfires usually come from lean conditions...and an engine running lean won't make anywhere its normal output power...

I'd check the fuel pressure first...

 

[Firemandave]

backfires usually come from lean conditions...and an engine running lean won't make anywhere its normal output power...

I'd check the fuel pressure first...

Fuel pressure is fine. Runs with normal output power for about 10 min then misfires and cuts out.

 

[makomark]

Did you check the fuel pressure with the power loss occurs as well as at the initial startup?