Planing? Prop? Performance? Help!

[ckone0814]

Re: Planing? Prop? Performance? Help!

Water is naturally going to fill in that tunnel, and flow over your cavitation plate at low speed, and as you try to plane, creating a problem

water flowing over plate is creating added downward force at stern maybe?

 

[Tail_Gunner]

Re: Planing? Prop? Performance? Help!

I have previously, given you my opinion on a prop choice and,
Thanks for the pics, but I'm confused, it looks like there is some type of "notch", "tunnel", in the bottom just before the prop, that might be causing some type of turbulence when you try to get on plane? I wonder if your cavitation plate needs to be flush with the top of that tunnel, or notch?
But, that don't seem right either, hence my confusion

Water is naturally going to fill in that tunnel, and flow over your cavitation plate at low speed, and as you try to plane, creating a problem IMO, but once you're on plane, the tunnel would be out of the water,,, I think?

But, having that trailing edge of the tunnel so far ahead of the prop, means that the flow of water will rise some from there as you're on plane (as normally happens from the trailing edge of any boat), that might be restricting flow, causing too much going over your cavitation plate, creating a restriction unless you raise the motor up some.

I usually dont respond to O/B's but isnt that cav plate higher than the hull....Pic's can be misleading...and if it is that could be the problem..Explaining why she sucks down so hard or bows up..its all in the balance.

You might also take a look at the back edge of the blade...It is missing paint quite high up the blade..That could be cavitation. I left out some info on the props i posted above...As Dee says a 15 will give you a better launch, but note a 15 SS will give you both the hole shot and top end...Simply said you wont lose a thing..it will act like a true 15 out of the hole but and a 17 pitch at wot..One of the benefit's of SS..

 

[MikDee]

Re: Planing? Prop? Performance? Help!

water flowing over plate is creating added downward force at stern maybe?

It's a fact, that when a boat is on plane, the water off the trailing edge of the transom actually rises right afterward, so that the ideal spot for the cavitation plate is just above it, or riding on it. This ideal height is to be determined, & varies from boat to boat. In essence, on planing, the whole boating package rises up as if on a shelf of water. This notch in the hull appears to hinder that process IMO, by filling with water from the start, and all through the process, until the boat is fully on plane, because it is 6" ahead of the trailing edge of the transom, and when the boat is on plane, I would say the trailing water in the center behind the notch is higher then anywhere else on the transom. Which would tend to be higher up on the leg, maybe even over the cavitation plate, causing drag. Hence my theory for raising the motor, but how high, I don't know???

On a normal tunnel hull boat, the water level on plane has to be determined, in order to set the cavitation plate at the right level, so as to ride at, or on the water surface at full plane & WOT (wide open throttle).

 

[ckone0814]

Re: Planing? Prop? Performance? Help!

you're right - I would say that trimmed full in, the plate is just higher than the lowest part (point of v) on the hull. how much higher? maybe an inch. the pics make it look a lot worse.

 

[MikDee]

Re: Planing? Prop? Performance? Help!

I am not thrilled with the notched transom hull design, but I'm sure if it's setup right (and if you're picky like me, this might be quite a chore) you should be fine!

Then again once you get the right prop, this hull design might not make a "hill of beans" worth of difference to bother to go through the trouble of trying to get it right after all

It seems to me, Century should know what they're doing, putting this notch in the transom, and it shouldn't really interfere with trying to plane off,,, What do I know? I'm only a peon But hey, they could be wrong

Though, I do like TG's reason's, & suggestion for a good 15" SS prop

 

[MikDee]

Re: Planing? Prop? Performance? Help!

you're right - I would say that trimmed full in, the plate is just higher than the lowest part (point of v) on the hull. how much higher? maybe an inch. the pics make it look a lot worse.

This shouldn't be an issue, as I said before the water surface will always be this high, or higher, on plane at that point.

 

[ckone0814]

Re: Planing? Prop? Performance? Help!

because it is 6" ahead of the trailing edge of the transom

Boat is not with me and my estimate of 6" is a probably a stretch - sorry. It's closer to 4 inches.

I have a call in at Century to see if they have a recommendation on the plate height for this year/model.

 

[Tail_Gunner]

Re: Planing? Prop? Performance? Help!

you're right - I would say that trimmed full in, the plate is just higher than the lowest part (point of v) on the hull. how much higher? maybe an inch. the pics make it look a lot worse.

Am i missing something here...the cav plate goes under the hull.....Un less he was using a set back..aka 1" up for every 12" back>

AKA a cav plate to high creates a vortec or whirl pool effect causing cavitation...as shown on his prop..From limited past experience 1 to 2" below the hull is std without the aid of a jack plate..

 

[QC]

Re: Planing? Prop? Performance? Help!

Do not change anything until after you have got a clean bill of health from Yamaha and retested. That "notch" in the stern is very common. I would not consider height an issue at this point at all. One change at a time . . .

 

[ckone0814]

Re: Planing? Prop? Performance? Help!

Am i missing something here...the cav plate goes under the hull.....

Ha Ha I'm sure you're not the only one I've confused! I'm throughly confused too but learning with every post of this almost 3 page thread - if that makes sense.


No, if you took a straight edge from the very bottom of the hull to the plate the plate would be just higher by an inch or so. The stright edge would pass over a 4 inch deep notch cut into the hull at the transom. Hope that helps.

 

[ckone0814]

Re: Planing? Prop? Performance? Help!

Do not change anything until after you have got a clean bill of health from Yamaha and retested. That "notch" in the stern is very common. I would not consider height an issue at this point at all. One change at a time . . .

you bet. thanks.

 

[Jdeagro]

Re: Planing? Prop? Performance? Help!

After reading more of the posts and looking at the pictures, I think that motor height, transom design, etc suggestions will make a difference once the core problem is identified and solved. You don't have poor performance, you don't have ANY performance. Make sure the engine is up to par, the prop is good, and the boat is not 1000 lbs too heavy.

Even if the prop is the same as the one in the test, try a new one to make sure yours is not defective in some way.

Let's get the boat up to poor performance first, then move forward with the many good suggestions from all of your friends here at iboats.

 

[Tail_Gunner]

Re: Planing? Prop? Performance? Help!

I am quite sure you need to lower you cav plate 1-2" under the hull...maybe or Dahadley or WH would come and clear it up. But everything you have posted in word's and pic's has shown as much...the prop paint at the back of the blade say's it all. Cavitation

1-2 read 2" cav placement under the hull will be a good placement...this is not a high speed hull thread looking for absolute top end WOT...It is a i cant get on plane thread...DH for future reference your input would clean this up a bit.

 

[ckone0814]

Re: Planing? Prop? Performance? Help!

THANKS again to everyone for their help and patience.

As many have suggested, we definitely won't be doing anything until we hear about the motor and getting a solid weight.

 

[MikDee]

Re: Planing? Prop? Performance? Help!

I am quite sure you need to lower you cav plate 1-2" under the hull...maybe or Dahadley or WH would come and clear it up. But everything you have posted in word's and pic's has shown as much...the prop paint at the back of the blade say's it all. Cavitation

1-2 read 2" cav placement under the hull will be a good placement...this is not a high speed hull thread looking for absolute top end WOT...It is a i cant get on plane thread...DH for future reference your input would clean this up a bit.

The paint off the blade could be from hitting a sandy bottom. I don't agree he needs to lower his motor, I doubt he's getting cavitation, but that's my opinion.

 

[ckone0814]

Re: Planing? Prop? Performance? Help!

another pic just for the heck of it

 

[ckone0814]

BAD INJECTOR Re: Planing? Prop? Performance? Help!

BAD INJECTOR Re: Planing? Prop? Performance? Help!

So the shop called - they found a bad injector. Replacement was ordered should be in any day.

We have warranty through June; should this be covered?

Anything else I should know or ask?

Thanks.

 

[QC]

Re: BAD INJECTOR Re: Planing? Prop? Performance? Help!

Re: BAD INJECTOR Re: Planing? Prop? Performance? Help!

Under factory warranty, yes, unless there are some weasel words or required maintenance that would not make sense to me . . .

 

[ckone0814]

Re: Planing? Prop? Performance? Help!

Shop says they're "not sure" warranty will apply, "could be due to poor maintenance", "we'll see what Yamaha says", blah, blah.

 

[ckone0814]

Re: Planing? Prop? Performance? Help!

Work is done, bill was under $50 for a little labor and an O ring. Warranty picked-up the rest.

So we'll be out on the water retesting this weekend (weather permitting). I've heard from a lot of people on this board and a few people in the business I know personally and it seems like the general thought is that now that the motor is good to go, she may still be under-propped. What am I looking for specifically that will tell me this, or help you all tell me?