Mercruiser 3.0 Alpha one gen1 backfires

[vinny957]

Was out on the lake for roughly 5 hrs had no problem with my boat on way back in boat backfired I shut down the motor to check out wat it was no obvious signs of a problem,
Now wen I try to start the bout it will not start and every 3 to 4 turn overs the boat backfires out exhaust. Just had carb rebuilt before backfire started

 

[alldodge]

Welcome

Start by doing a compression test

Most likely you have a burnt or warped valve

 

[vinny957]

Thank you I will do the test today and see the video below is what it's doing

 

[alldodge]

Do check the distributor to verify the hold down bolt is tight and it cannot be turned