1972 Marlin Leo Jet 455 -now afloat looking for info

[Tail of the Rooster]

Yup - we are all arriving at the same conclusion. Lean misfire - a friend has another carb I am going to try but that will have to wait till next weekend.

[Dave01]

Aha! I take my suggestion back, you're right its most likely the carb. Like 455maveric says you're going lean, aren't feeding fuel to match the load. Sounds like a carb rebuild is needed.

[Tail of the Rooster]

OK - next question, this is a 17' 8" boat with a 455 Olds 365HP Berkley JC with place diverter, weight 1785 pounds. How fast should this boat go? Anyone have any ideas?

[Tail of the Rooster]

How fast will the boat go? 1972 Marlin Leo, 17'8" 1785 lbs, 455 Olds 365 HP?

[Dave01]

Probably a close match to my last boat, an 18 ft. Avenger with stock 455 Olds and 12JC-A pump and diverter. Before pump rebuild, around 55 mph. After rebuild about 58 mph.

Assuming you have an A impeller, fairly straight bottom, and reasonably tight pump, you should see mid 50's to max of low 60's, at least that's my guess.

[Bies]

A lean condition will back fire, Fuel filter at the carb, fuel Pump?

[Tail of the Rooster]

It isn't the fuel pump - the issue appears to be the right side of the engine only by looking at the spark plugs. The fuel filter is new. Back to the carb.