I also have a vintage (from 1978) Ford-Lehman 120HP on my boat. I have resisted suggestions from my shipyard (Hinckley's) to "upgrade" to a Yanmar
or Volvo Penta
. I've resisted these suggestions for the past 15 years, because that old Ford Lehman is simple and reliable (as long as she has air and fuel
- she runs!). But as an old engine some things wear out and need replacements
- and the weak spots seem to be the heat exchanger
and the exhaust system. However, these are not in-frequently found on eBay.
Bottom line here, you may find it cheaper and less stressful to replace the exhaust manifold than attempt a repair - which I understand can be tricky and may fail.
In addition, darylat8750
offered an excellent suggestion. I have called Bob and Daryl Smith a few times over the years. They are knowledgeable and always helpful.
There is a knock-off to the Ford Lehman 120 - Ford Saber 120. They used to be in Florida
. You may want to do a websearch. They used to use the Ford 120 engine for their conversion (now they use the Perkins
120 if I recall
Older boats within Grand Banks Trawler
community are frequently powered by Ford Lehman 120's and have had active web communities. I have occasionally gotten onto their "chat rooms" (even though I have a sailboat) and they have been very helpful in the past.
I'm sure that you know, the Ford Lehman is basically a marinized Dorset British truck engine and many old tractors in the UK and elsewhere are powered by this engine; meaning that parts
are readily available - just not at, say, West Marine
Hope any of this helps.