19' new bayboat porpusing question

[brent doherty]

i bought a new clearwater 1900 bay from dealer in dec 06 and have had problems with porpusing since day one. originally it had a yamaha f115 and i had it upgraded to a f150. on the original test drive (f115) noticed it porpused bad at 1/2 throttle but cleared up a wot. same scenario with the f150. this is not my first boat by no means but first time i have experienced this problem. i have tried everything i know to do ( engine position up, down, all inbetween, various props, jack plate, trim tabs ). it will quit the bucking with the tabs run down but then lose all my efficiency. bow plowing, hard to steer, lost 10 mph top end and 1k rpm. run the tabs up and it is like taking the brakes off and then starts to buck. i have the engine mounted as high as it will go on the jack plate without losing water pressure ( installed water pressure gauge too ) and it is the best i can get it. i currently have a 4 blade stainless stiletto prop ( 143/4 x 17p ) running 5900@wot (tabs up)trimmed due to the fact that the factory yamaha black steel 3 blade ( 141/4 x 19p ) kept blowing out around turns due to the engine being mounted so high. i may be thinking about this wrong but it seems the tabs are just compansation for another problem? does anyone have any suggestions or know anything about this particular hull? or maybe the hull is just defective? looks like there is a slight belly about half way down the keel? thanks for any idea's or info. brent.

 

[Tail_Gunner]

Re: 19' new bayboat porpusing question

Are your trim tabs mechancial that is do they self adjust, are they manually controlled or are they in a fixed position? That 4 blade prop you have really has a lot of lift and can set off oscillation's quite easy, well i have a 19 foot bay boat it's a 215 horse I/O at about 27 knot's trimmed out no tab's it will porpoise if it hit's a 2" swell with that prop and cannot do it or will not do it with a factory 3 blade, sound''s like your tab's are helping thing's along here a bit..

 

[ondarvr]

Re: 19' new bayboat porpusing question

What does the dealer have to say about the problem?

 

[brent doherty]

Re: 19' new bayboat porpusing question

Are your trim tabs mechancial that is do they self adjust, are they manually controlled or are they in a fixed position? That 4 blade prop you have really has a lot of lift and can set off oscillation's quite easy, well i have a 19 foot bay boat it's a 215 horse I/O at about 27 knot's trimmed out no tab's it will porpoise if it hit's a 2" swell with that prop and cannot do it or will not do it with a factory 3 blade, sound''s like your tab's are helping thing's along here a bit..

they are manually controlled - lenco. the boat also porpused with the stock yamaha 3 blade prop too. i just don't think i should even need the tabs for a routine ride up the river?

 

[brent doherty]

Re: 19' new bayboat porpusing question

What does the dealer have to say about the problem?

dealer has no clue? i guess that is why i got the boat so cheap! i am in the process of getting in touch with the manufacturer. also have an e-mail in to a different dealer for same brand of boat with these same questions. guess i'll wait and see.

 

[Jdeagro]

Re: 19' new bayboat porpusing question

Porpoising is caused by poor balance for the most part. Since you have helm controlled trim tabs, I would suggest that you adjust them in very small increments and give them a few seconds to work. Also the motor trim should be adjusted to a vertical position when cruising ( no sence having two things trying to adjust hull angle and balance. Next check the motor height. It may be off.

Call if you wish. Nauticus inc 800-233-0194 ( you should be able to cure the problem with your existing equipment).

 

[MikDee]

Re: 19' new bayboat porpusing question

I would say to set your cavitation plate paralell (in a straight line) with the boat bottom to begin with, and leave the tabs alone (up), then try it. If you have a problem then, either you have too much weight forward of amidships to the bow, or you have a slight hook in the bottom.

 

[studlymandingo]

Re: 19' new bayboat porpusing question

The hook sounds like a possibility. Take a long straight-edge and set it on the keel, if there is any space along the straight-edge, then you have a hook.​