Question...

[THEFERMANATOR]

Originally Posted by Destroyer

Do you know what the normal compression is on one of those engines? The dealer told me that this engine has 80-85 psi on all cylinders. I know that my 91 has 93-95 on all cylinders, but 80 sounds a bit low?

As to the Merc, I have no doubt as to the accuracy of your statement that it's advisable to go with a 25" lower unit with a spacer kit, but the engineer in me has to know why. Aren't the gears and such identical in the 20 and 25's, the only difference in them being the length of the drive shaft? What is it I'm missing?

The compression on the 60 degree loopers should be up around 110-125 I believe, but it can vary from year to year depending on what style porting and pistons were put in it. The problem with using the 20" lower is the driveshaft extension you have to put onto the driveshaft of the 20" lower. They can get looose and cause vibrations over time is what I was told.