Can or how can you tell drive ratio on boat
 

OK, I've been messing around with this problem all season lets see if any one else has an idea.
Both engines are brand new, built by the same shop with same parts, compression ect., both props are the same.
one engine will spin 5500 happily, the other will spin 4500-4700. The slow one will spin to the limiter, with no load. The slow one burns 2x the fuel of the fast one, with no black transom and clean plugs. I've checked the timing and done all the basic mechanical checks to the engine, I don't belive that is the problem. I've swapped the props side to side(same rotation) with no change in the results.
I'm starting to think some one changed the drive ratio, in the slow one, can I tell the ratio by spinning the engine by hand and counting the prop revolutions or does the drive have to come off ?
Thanks

Yes, rotate the engine. ( drive in gear)
( I'm assuming the 2 popular bravo drive
ratio's here)
A 1.5:1 ratio, one engine revolution
equals .666 prop rotation (or approx
2/3 of a revolution)
A 1.36:1 ratio, one engine revolution
equals .735 prop rotation ( approx 3/4
of a revolution)


jt

Or putting it another way, if the engine rotates 1.5 revolutions and the prop rotates once = 1.5 : 1 ratio
If the engine rotates 1.3 revolutions and the prop rotates once = 1.36:1 ratio.

Sonic, First I was thinking maybe you have TRS's since your boat is a 1987, but then you mentioned same rotation drives which sound like early alpha's? They make alot of ratios for the alpha drive but I dont think anything less then 1.5. Either way alpha or bravo, then Dennis was right and spin the motor. TRS, then you have to pull the drive, but the only factory ratio for the TRS was 1.5