Chrylser 125 not revving past 4000 - or is it?

steveclv

Petty Officer 1st Class
Joined
May 12, 2010
Messages
242
My 84 Chrysler 125 on a 19' Bayliner Capri is now running very well except for a small backfire when starting and the usual smokiness.

Out on the lake, the boat gets on the plane quickly and the engine is smooth - however it will not rev past 4000 on the tach.

With just me in the boat, I checked the GPS again this weekend and with water temp of 91F we were running at 42mph.

If I raise the engine on the trim and then do a hard turn to cavitate the prop - the revs only rise a couple of hundred rpm to 4200.

The prop is a 13*19 Cupped aluminum prop that looks as though it may be original.

42mph seems about the right max speed for a 19' boat with 125hp so could it be the tach that just reads low? Is a failing tach something that happens a lot? The instruments are all original.
 
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