drpete3

What kinda speed have you seen Mike?

sommerfliesby

81 with Bravo 30s...but I ran out of room on Lake Macatawa. Should get some good numbers this weekend at South Haven if the big lake is smooth...

rclaws35

The plates work

sommerfliesby

I'll be putting the plates on as they provide a platform for my drive showers as well.

Ran this weekend with a set of Hydro Quad IV-Xs...bow-lifters. Boat went 81.5 at 5300 rpm. The slip calculated to 6%. Where do I go now?

29scarab10

How many rpms you willing to turn your motors?
Allen

sommerfliesby

5500. They are built to turn.

RaggedEdge

Would they also help when seeing a lot of cavatation while getting on plane?

29scarab10

Start looking for ways to free the boat up some. I know that on that year 29 and 32 they had blocks on the trim tabs that the 35 might have had. If they do, take them off and run the boat, when you get the boat as fast as it will go and you are confortable driving (it may try to chine walk), cut the blocks to fit. Usually about 3/16 cut off will help.

I also know that alot of people will disagree but every boat I have ever owned liked zero toe in the drives.

Try to keep as much weight (extra stuff) in the back half of the boat (for sure keep heavy stuff out of the nose of the boat) and yes a 25 pound tool box will make some difference.

Use a level or angle gauge to make sure both drives and trim tabs are traveling the same on you indicators.

Make sure there are no blunt edges or dings in your skegs.

Double check you total timing and your afr. It is not uncommon for the dyno afr to be perfectt and then be really rich in the boat.

Keep playing with props. If my math is right you used 26 quad 4 x to get to your best speed and the 30 pitch bravos were very close. That is a big spreed in prop size with little change.
How many rpms were you turning the 30's? Someone offers to loan you a prop, do not turn down that oppirtunity. Have seen some crazy things that i thought would not work but turned out to work great.

Dont give up.
Allen

sommerfliesby

Thanks alot Allen. I put the anti-cav plates on yesterday, and I'm going to try to get some 28 Hydros to run this weekend. The cruise was WAAAAY better with the 30 Bravos....@ 4k RPM, I was 63 mph, whereas with the 26s I was only at 55. (This was with the trim all the way out at 4.5 - 5 pins...previously, I always ran at 3.5 pins).

The boat doesn't seem like it wants to free up in the back end...even with the bowlifting props.

And I nowhere near giving up....I'm just getting started!
mike

techman

Not to be another smartass but they are anti-ventilation plates not cavitation plates. Cavitation is super low pressure causing the water to boil and vaporize on the blade. The boiling leads to wear on the blade.

Ventilation is the result of air or exhaust gases being pulled into the propeller blades. This causes the blades to lose their grip on the water, the engine RPMs go up and the forward speed of the boat is reduced.

Sometimes when the propeller RPMs increase, it can also cause a massive cavitation, which only compounds the problem. Most outboard and stern-drive engines have anti-ventilation plates made onto the lower unit housing directly above the propeller. Many people mistakenly call them cavitation plates or possibly anti-cavitation plates, but that is incorrect.

The anti-ventilation plate does not stop or help prevent cavitation. Its sole purpose is to prevent surface air from being sucked into the negative pressure side of the propeller blades