3.0 135 hp popping through carb

[SSGTUSMC]

I have a 2006 Bayliner 175 with Mercruiser 3.0 (135 hp) alpha one. I was running out about 4200 RPM when it suddenly started popping or backfiring through the carb. Had been running off and on that day about an hour. Temp was 175 and oil pressure was and stayed normal. There is no other odd or medal to medal sound from the engine. Not medal shaving on the dip stick. Cam lube or broke valve spring come to mind. Any ideas.

 

[Don S]

Re: 3.0 135 hp popping through carb

Run a compression test and possibly a leakdown test. Follow this Service Bulletin Could be a valve leaking, or sticking.

 

[Haut Medoc]

Re: 3.0 135 hp popping through carb

Welcome to iboats....
Water in fuel.....
Have you checked your water separating fuel filter?.....​

 

[SSGTUSMC]

Re: 3.0 135 hp popping through carb

Will run a compression test. I'm an F/A-18 mech I don't know the first thing about a water separating fuel filter. Is it like a normal in line fuel filter? What do I look for? Thanks gentleman!

 

[180shabah]

Re: 3.0 135 hp popping through carb

I don't know the first thing about a water separating fuel filter. Is it like a normal in line fuel filter? What do I look for? Thanks gentleman!

With a 3.0 you probably don't have one, they were optional. Just in case though, it looks like an oil filter(spin on steel canister). Follow the fuel line from carb to tank, if you have one, you'll find it easily. If you don't have one, you should get one. They are available just about anywhere for $25-30 plus fuel hose(which MUST be marine rated) and clamps.

You should also double check that your vent line is clear. It should run up continuously from the tank to the vent with no dips that could trap water or fuel(like the trap under your sink).