-2s
 

Finally got to run my boat this weekend with the -2 lowers and my new motors. All things considered, she ran on flat water very similarly to the normal length Bravos. Came on plane nicely, ran on rails at speed, turned well. Problem was when I went out in some bumpy water, my props kept blowing out upon re-entry. I was throttling like I always have (I'm not Saccenti, but I can run a boat in the rough)...but it was crazy how I about stopped every time I came back in. Then the props would grab and it would take off again.

I was trimmed to the spot where I always ran the boat...3-4 pins. Is this too high? Should I be keeping the drives tucked more now that I have the shorties?

Need some help from those that have done the same thing...

Mike, I would PM monstaaa and see what he recommends.

Good luck.

What props you running? Are you sure that you are not comming of the throttles to much?
Allen

Yeah, What props? and did you add the extra cavitation plates to the uppers?

No extra cavitation plates and it happened with both 26 Hydros and 30 Bravos....and I'm pretty sure it isn't that I'm pulling back too much...I have done that in the past and it hasn't resulted in blowout...

I think I would get and install a couple of these http://www.imcomarine.com/cal_store/...plate-kit.html
Allen

I've got them, but didn't put them on. Why do you think that would help with blowout?

Not trying to be a smart butt, but technically you are not blowing out because to blow out speed has to be increasing by definition. You are cavatating and these plates are generally refered to as anti cavatation plates.
Allen

Maybe you ARE a smart-butt...with an emphasis on the "smart." :) I'll definately put it on the list of things to try!

Try the plates

What kinda speed have you seen Mike?

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...

The plates work

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?

How many rpms you willing to turn your motors?
Allen

5500. They are built to turn.

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

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

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

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

Which way you spinning your props?
Allen

all good points/tips

Spinning in. Techman, what you described is exactly what I had happen.... Hopefully they work.