I bought a pair of Volvo drives from a Cig 28 that was in Ohio, rebuilt them and installed them on my Magnum 27 . . they are 270T drives . . but without serial numbers and I foolishly never figured out the gear ratios before installation.

I've run the boat with 15 5/8" x 21P Solas props and the GPS speed was 67 MPH at 4400 engine RPMS , there's more left but this calculates out to a 1.1:1 gear ratio . . . ?? Which makes no sense . . does anyone have any idea as to what was original to a Cig 28?

Mario

Volvo 270's were offered with 1.61, 1.89 and 2.15 to 1 ratios. To my knowledge there were no 1.1 to 1 ratios. Since your speed was clocked by GPS that's probably correct. I would say that either the prop pitch is mis-labeled or the tach is not reading correctly.

Ben

My 28 SS has TRS, I have no idea of the ratios

Mario,
Something is very off with these parameters as you already know. It would be a relatively simple thing to pull a drive and count the input shaft revolutions with one turn of the prop shaft - at least you would know the ratio. Bill