Marine (ized) engine horsepower loss over time

And stoneage a 1949 cessna is basically the same as a 2009
carburettors and magnetos??
The industry is happy where it is no new entrants therefore no need to change and no EPA to go and change that

 

I don't think air-cleaners mean a thing to the gas engine.
But to the Carb they sure do. I've seen the Venturi almost gouged out on engines that spent their lives with the same Air filter.

Almost every carb that's been on a Marine engine operating in Salt water, inhaling salt Crystals, has a worn out venturi also.
Thats where a lot of the loss of HP comes from in a Gas engine.
A Venturi made of Carbide Steel would probably maintain its HP much longer than the Pot metal carbs would.

Diesels are not bothered with little things like Breathing salt air.

Having had the experience of rescuing an engine that was over heated repeatedly, I noticed the loss of HP. It started and ran OK, just soft on acceleration at working Rpm's.
The Rings were cooked. They just wouldn't seal good at the higher Rpm's.

I believe the extreme hi torque load on a Marine engine, all its life, does about the same thing to the Rings. They just don't seal as well once they've been cooked. All that load, all the time, is the same as cooking.

Why Diesels don't suffer the same fate probably has something to do with oily cylinders. Just a guess there!