Bouncing boat

Sivart

Petty Officer 2nd Class
Joined
Jul 1, 2003
Messages
105
I am new to this board but have been reading it for sometime trying to cure a problem with a porpoising(sp?)boat. I have an 86'Bayliner Trophy bass boat with a 85 hp Javelin motor. I have tried about everything that I have read on this forum to fix the problem. I have tried 3 different brand of hydrofoil fins, the Nauticus trim tabs, several different props, and a jackplate. Nothing has helped this boat. The jack plate is the only thing that really made a difference and it was for the worse. This leads me to think that the boat is too heavy at the rear??? I have tried adding about 250lbs to the front but that did not help. Does anyone have any ideas that I have not tried. My next option is to sell the boat.
 

Sivart

Petty Officer 2nd Class
Joined
Jul 1, 2003
Messages
105
Re: Bouncing boat

I did forget to mention that I have tried from the highest to the lowest motor position and it did not seem to help the problem at all either. I have done a search on this problem. That is why I purchased the trim tabs.
 

magster65

Commander
Joined
Sep 1, 2002
Messages
2,573
Re: Bouncing boat

Trim the motor down all the way and add more bow weight until it stops.
 

Jack Shellac

Lieutenant Commander
Joined
Aug 7, 2002
Messages
1,661
Re: Bouncing boat

Since you seem to have tried everything else, my guess would be that you need to go to a four blade prop. This is the usual solution when everything else fails. It provides more thrust , but you may or may not lose some top end.
 

Dan180cc

Seaman Apprentice
Joined
Jun 4, 2003
Messages
40
Re: Bouncing boat

Sivart<br /><br /> I own a sea-pro 180 center console that had a problem a lot like yours. Weight and ballance are<br />the things working against you. I did notice on my<br />boat that the problem was at its worse when I had 1/2 a tank of fuel. The fuel tank was under the floor below the center console when the propoising<br />started it was small but got worse to the point it became unsafe to drive. 42 gallon tank provided to much room for the gas to move in.<br /><br />I took the boat back to the dealer and they had 4<br />tech,s checking it out with the Sea-Pro tech on the phone. They took some measurements related to the AV plate and hull using a yard stick at the center line at different trim positions.<br /><br />They changed the prop to a 14x21 from a 14x17 and <br />tested the boat again. Well, was a differnt boat after that. I could trim out with no problems at all and it gained 7mph on top end. The only down side was I gave up some hole shot but I am not racing anyway. The prop added so much more lift to the bow the amount of gas doesnt matter any more. If you could find a prop on ebay for your engine with more pitch this may really help with your problem. Most of them sell for around 45-50 bucks. Good luck Dan. :)
 

Sivart

Petty Officer 2nd Class
Joined
Jul 1, 2003
Messages
105
Re: Bouncing boat

Dan, and everyone else. Thanks for your help. My boat came with a 13 x 19 prop. I called the dealer and they confirmed that is what it came out with from the factory. I have tried a 14 x 17. It came out of the hole fast but would not get over 28 to 30 mph and it still did not fix the problem. This boat does have a 22 gallon tank and it is positioned just behind the seats. I have noticed the less the gas the less the boat bounced. This is the reason why I tried the weight up in the front. The problem is the tank is low in the boat and is practically built "in".<br />If I trim the boat around 35 mph the motor will lift the front up considerably but as soon as I hit a wave the bouncing starts.Sometimes it seems the bouncing starts for no reason. Will a 4-blade prop make that much difference? I am open to anything. Thanks again.
 
D

DJ

Guest
Re: Bouncing boat

Porpoising is a true sign of too much weight aft (rear).<br /><br />Props can help, but probably not the answer. Engine height probably won't help either.<br /><br />Solutions:<br /><br />Move some weight forward. Batteries, etc.<br /><br />Trim tabs.<br /><br />Engine fin (cavitation plate).
 
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