Is the air filter really necessary ?

[NormanS]

I forget the exact source, but I was once told by an engine builder of some repute that it had been found that doing away with air filters on the engines in one formula or another of racing car in the quest for minimum intake restriction gave a detectable increase in power. The problem was that the gain was short-lived. After a race or two, the filterless engines had a power output lower than the engines with filters. The culprit, dirt and dust deposits in the inlet tract and premature minor wear within the engine itself caused by the aspiration of abrasive particles.

Relatively dust free environment or not, I wouldn't run a boat engine without a filter.

My boat never competes with racing cars.

 

[superheat6k]

Perhaps a key point here is what boat type, although I would prefer to see a filter regardless. For the motor boating brethren the engines will be large individual value and a high % of the boat value. Keeping these properly set up will easily be picked up at sale time, and is not a corner to cut.

However, for the yachtie only using his engine for a few hours / litres per year perhaps not as critical as decent standing rigging, and shapely well fitting and not over stretched sails.

I for one would walk away from a Mobo with engines of dubious service history, but a good starting and clean engine on the sailboat would satisfy me even without much service history.

 

[LittleSister]

The 1950's motorbikes I used to ride had no air filters - just an open bellmouth on the carb intake - and ran fine. On the other hand, they certainly didn't run for tens of thousands of miles without rebores and other attention!