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Cavitation!!!! Please help!

C

Come Monday

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Sarasota FL
So I got the new boat. It's a 2350RBR with a 20" transom and a 20" f-200 Yamaha. The prop is a SS reliance series 14-1/2 x 15.

The ride just isn't smooth. You can watch the rpm's jump while underway straight, not to mention the hard turns. Loaded with people it feels front heavy and you can feel the cavitation when driving.

Where do I start with this - it can be a number of things I presume.

The motor is placed in the second hole and can be lowered one more hole.

Super irritating - any help on this issue would be tremendously appreciated! Thanks!
 
Where is your trim set? Have you tried to trim up & down, what happens?

Steve
 
I would start with your dealer, they should make it right. There are times on our boat when I have to move people around when they all want to be up front.
 
You got the boat that supposedly really performs.  And with the 1.86 gear ratio, you have the right propeller.

I agree about taking the boat back to the dealer.  They probably need to start by dropping the motor down on the transom.

Is your passenger load sitting toward the front?  Sometimes you've got to ask'em to move to the rear to get the motor deeper in the water.  My old pontoon was like that, and we could never get it to quit ventilating with 3-4 people sitting up front.
 
Thanks for the advice everyone.

Here's what I've done.. I called Bennington directly and explained the situation and they were fantastic. In fact I wish I could've bought the boat directly from them and left the dealer out of it. The gentleman I spoke to contacted one of the engineers and rattled off my specs. It turns out they have tested my exact boat with an F-200 with the reliance series prop installed on it, but their optimum performance bulletin had it installed in hole position #1. My dealer has it in #2. It makes sense to lower the prop in efforts of stopping ventilation - so I'll try this first and see what happens.

If you need to lower the motor to the bottom most setting, why wouldn't they choose to put a 2" shaft extension in so it can be mounted in hole #3 or #4. This would put the prop where it needs to be and also get your exhaust intake on the back of the cowling off the water line so you're not sucking water.
 
Keep us updated as to the result of lowering it.
 
Would still like to know your trim setting(s).

Thx

Steve
 
I've been told by the service manager to leave the trim all the way down. He said its a set it and forget it.

I, of course, play with the trim like any of us would. It's weird though. When I'm underway, say, at 3500 rpm when it's a 20mph cruise on plane, if I trim the motor up 1/16" above half according to the gauge, it ventilates and the rpm's jump. I was able to trim my last boats trim all the way up to the top, underway, and all that would happen would be the bow would lift - no ventilation.
 
Any idea what hole the dealer has your motor mounted at? I had a discussion with my dealer about this last week and came away very skeptical with his choice of hole 2.

I have a new 2275 GCW with ellipticals, strakes and a 150 Yamaha. Haven't floated the boat yet, hopefully this Friday for my checkout ride. They will fit a prop working with correct rpm's in mind. If it sucks too much air when hard over or trimming then I'll have them drop to hole number 1. I'm curious where other folks with the same hp and bottom configuration are at.
 
Totally agree with my service manager being an idiot. It's been a hell of a ride. I'm actually at the point of paying my marina to lower my motor so I don't have mess with the dealership shenanigans. I feel like they're better suited for the fixes. It's going to cost me a few hundred bucks, but in the long run it's going to be easier and less to argue about. It's a boat I guess.
 
It should be a very quick and easy job to drop the engine a notch on the transom.  I too agree about the service manager. 

Power trim is there for a reason, and you should be able to raise the nosecones out of the water without ventilation.  That's where you get your speed and fuel efficiency.

My 24SSLX with the F150 is sitting 3/4" off the transom in hole #2, and it runs great.  I run my engine a little high where I do get a tad bit of ventilation on takeoff, but it settles down quickly.  There again, I've got a 2:00:1 gear where the F200's spin the prop a little faster with their different gear ratio.
 
The best way is to view how the water flows above and below the cavitation plate while under way at a comfortable cruise. You don't need WOT to do this. This post has a video on how to read it http://club.benningtonmarine.com/index.php?/topic/2410-triming-a-pontoon/#entry23065

It doesn't matter that it's a Verado, the same principle applies. This is exactly how my dealer did it. Engine set too low as in "buried", it'll be slow and the bow won't come up no matter what you do. Too high and it slips and/or porpoises. 
 
I agree with the others, there is no set it and forget it on trim settings.
I am constantly adjusting my trim based on knots and how many people on the boat.

You didn't say if your motor is electrically trimmed? (do you have the trim toggle switch on the throttle?) OR is it a heave the motor up/down and slide the rod type of trim.
 
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