377 mag opinions?

[lrdchaos]

I’m in the market for a boat and found A 2015 with a 377 mag That has 95 hours. Are there any major issues with this engine? I had a 5.0mpi for 12 years that had little to no issues, so I’m not new to boats or mercurisers, just this engine.

 

[alldodge]

The 377 is a virgin bore 350 with a stroker kit. If you took a 350 and bored it to .030 over (during a rebuild) and put the same stroker kit you come up with a 383.

The only thing I don't like about motors after 2009 is they have Catalysis exhaust. The CAT's have had issues with the poppet valves on the cooling system and other things with O2 sensors. I for one plan to never own a boat with CAT's

 

[Searay205]

If anyway to avoid Catalysis exhaust avoid. immediately get a CP performance cat simulator. Rear oxygen sensor rot away every other year. install cat simulator which eliminates rear oxygen sensors and remove catalyst put in bag and store. If manifold replacement is necessary go back to old style only modification is spacer for pre cat oxygen sensors. Truth be told the new manifolds may last a very very long time. different geometry and design vs old, no corners for debris to accumulate in and overheat and crack. They are heavy 90 lbs each vs old style of 40lbs? I have not heard of one catalyst manifold cracking or getting a hole....

 

[mpeare351]

Hmmm.... I have a 2015 Formula with twin 377 mag's. Seacore. I'm having that issue with the catalysts and with O2 sensors as well. It's driving me nuts. The repair man has to keep coming back.