I will say I'm surprised so many old boats still have the old Lehman's and have not been re powered. They seem to be survivors.*
At the risk of appearing to contradict myself, the Lehman engine is a very robust, long-lived engine.* The quoted average lifespan of an FL120 in recreaional use, assuming it's operated and maintained in accordance with the design intention of the engine, is 12,000 to 14,000 hours before needing an overhaul.* In commercial service on the Washington State ferrry system (I assume running generators or hydraulic pumps) some FL120s went as much as 25,000 hours according to Bob Smith at American Diesel.*
This long core life does NOT mean it won't need some major work along the way with the ancillary equipment.* It will need at least one fuel injection pump overhaul if not two or three, it will need water pumps every so often, raw water pumps every so often, valve adjustments, exhaust elbows, fuel lift pumps every so often and so on.
My preference for newer engines is not because the Lehman is short-lived or unreliable.* It is neither.* I happen to prefer a more modern engine that produces more power per pound, is smoother, quieter, less poluting, and has much longer service intervals.
But in terms of reliability and longevity, a Lehman engine in a boat is not a detriment.* There's not much to break if it's run and maintained properly which is why there are so many of them around in so many types of boats still today.
As has been mentioned before, replacing a Lehman or a set of Lehmans is not an inexpensive proposition.* Installing a six-cylinder engine or engines of similar or better performance usually takes you these days into at least the 150 hp range--- Luggers, for example--- and they are not cheap.
So unless a Lehman actually fails to the point where a total rebuild is required, re-powering a boat with one or two perfectly operating Lehmans in it is simply not cost-effective no matter how much the owner may wish he had newer engines.* So that's why there are so many Lehman-powered boats still around.
-- Edited by Marin on Wednesday 17th of November 2010 12:56:20 AM