Repropped....big difference

[shrew]

1997 2800 SCR
single 8.1L (496)
Bravo 3 (2:1)

During winter maintenance this year I had removed the props and were cleaning them up. The splines on the prop hub were cracked and some were sheared off. These were both 3 blade 24pitch props. I have always felt they were overpropped despite many people claiming this was a great setup for the B3 with a big block. I hit something 2 seasons ago that sheared the gears on the lower end of my old B3. I suspect this is residual damage that wasn't so obvious immediately after the hit.

I could never seem to get the boat above 4000 - 4100 RPM MAx RPM is supposed to be 4800rpm. I could never get the boat above 30-31 kts.

So I did a bunch of reading and ran the numbers through the Merc prop calculator. I even called US Marine who confirmed they never shipped my model with 24 P props.

I replaced with:

FWD: 4 blade 15.75" 22.5p
AFt: 3 blade 14.25" 22.5p

RESULTS:

-> Time to plane cut in half
-> Max RPM 4750
-> got speed up to about 35 kts but too choppy to continue.

The odd part was, i was expecting the rpm to increase in order to maintain my regular cruisng speeds. It didn't really change. I used to get about 22-25kts at 3800 (depending on tide, wind, current, etc (especially tide)). Now I'm getting about 25kts at 3850. I expected to have to go higher.

What I didn't expect is the difference in the sound of the engine. It just sounds like it's running smoother. Like it's not all loaded up. These things don't make any sense to me. But I am extremely happy with the improvement in performance.