Originally Posted by bobl (Post 1985276)

I think what Strip is trying to say is a method to test the flywheel hp IN THE BOAT. Then you could tell exactly what the drive was costing. I believe the exaust routing in some boats (like Rage's Nordic) costs more power since it makes 2 sharp turns after the water mixes with the exhaust.

Originally Posted by bobl (Post 1983745)

Here are some numbers to stir things up. I just dyno'd a Whipple charged 383 on the prop shaft dyno. On the engine dyno it made 555 HP at 5800 RPM. Guess what it made at the prop shaft???? 490 The only difference was that the boat has Gibson mufflers. They aren't supposed to cost any HP, but even if they do that's a 65 HP loss running through a Bravo X drive. Interestingly the percentage loss increased with RPM. At 3600 it shows a 10% loss. More like 12% at 5800. So, on a 300 HP engine a Bravo does cost about 30 HP, but double that and the loss goes up proportionally. I'll be testing some other engine packages this winter so I'll post more results.

Originally Posted by Rage (Post 1990314)

I just called Mercruiser tech support and asked what the hp loss is for a Bravo1 drive. The answer was : 10% for X or XR.
Comment?

Originally Posted by cobra marty (Post 1990825)

To test the HP at the engine while in the boat you need my On-Board-Dyno setups but it will only work with a stellings box. You could actually use mine and the propshaft dyno at the same time and do simultaneously testing be it with div=fferent strain guages but if the calibration is accurate it wouldn't matter.

Originally Posted by Strip Poker 388 (Post 1990511)

So if I have 848hp and running it tru a XR its robbing 10% up to the factory rated rpm and if I am pulling it up to 6000rpm it would be more than 10%, Also since I and running a B Max with larger gears and bearings up top it would be even more of a HP loss. guessing 15%?????

127 HP loss:eek: :eek: