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Re: 2GM 15 dies when I put it in Fwd
OK, you mentioned just now that you have a folding prop. That partly explains why you get revs in reverse, because some of those props are pretty useless going backwards and do not stay fully extended. At idle in reverse it is probable that the blades are hardly open at all. Therefore there is not as much load on the engine in reverse.
So, if the shaft turns freely and is not moving forward under load to put stress on the gearbox or some other part of the shaft log, it seems simply a case of the engine not making power. Often a diesel with some air in the fuel system will start and run, but never make full power. It could be as simple as that, or as others suggest could be low compression (you hope not), injection timing out of whack (easy fix, if you have the book on it), clogged air intake (even easier), clogged exhaust elbow (easy enough but dirty job).
Just work through it starting with the easy jobs first.
Last edited by arvicola-amphibius; 05-24-2013 at 12:57 AM.