porpoising

[Burger]

My 16ft stratos tends to porpoise when I'm up on pad good usually around 32-35mph. I can get it up to 40 but I need a seat belt to stay in the boat. How can I fix this? The motor is mounted to the transom. Do I need to move it down a notch?

 

[Bubbakat]

You might try shifting some of the weight to the front of the boat to see if that will help or trim in a little until she gets full speed past the problem point then trim out for more speed. That can be caused from overpower or motor set to low or high wrong prop. Always try one thing at a time so you will know what you did to correct it. I have seen it on big moter bass rigs so bad that they had to install trim tabs to correct it.

 

[Burger]

Thanks BBK...

 

[SNUFFY]

I`d try raising it up a bolt hole at a time.The hull will follow the motor up to a certain extent. It`s amazing how much difference it can make. If I`m remembering correct , the early Stratos were made out of Allison`s used molds, A tri-hull type with the outside sponsons cut away about 3/4 of the way back.
I had an Allison 15` with a 140 Johnson and a 6 '" jack. It would porpoise some with livewell full and heavy load even after raising it some. When I repainted the boat I fiberglassed some wedges on the outer edge on the back corners of the bottom of the boat.The wedges were about 8"long x 6 " wide and about 3/8" thick at the back tapering to zero at the front. Never porpoised again.
As Bubbakat said sometimes the balance of the weight in the boat can make a big difference. Get as much of the heavier stuff toward the back as much as possible.

 

[finbully]

My Z21 does it at about 3100 r.p.m. (when I'm trying to run in economy mode). emoSmile I trim it down a touch and it goes away.

 

[Burger]

Well all the weight I have in the back is three batteries, gas tank, and motor.

 

[Guest]

There are two other ways to git rid of the porposing, buy a set of trim tabs or add a whale tail to the motor, the whale tail is cheaper.

 

[digitalcb]

Every answer here seems right. You either have to lift the back or lower the front. I agree with Doc1 that the whale tail is cheapest. My experience is that it will allow you to stay in the "economy" range and save gas money.

Of course a lot of boaters don't like to drill extra holes in their equipment. As for me, it ain't really mine till I've modified it. emoLaugh

 

[ole blue]

Whale tale all you need

 

[Burger]

It had a whale tail on it and it still did it. I just recently took it off. The whale tail had eventually cracked the cavitation plate where it was bolted on.

 

[beetlespin]

Stratos boats sometimes like to do that. My 200XL I just traded did it at full throttle. You might try a 4 blade prop if you don't already have one but other than that I don't know.

Lance

 

[ditchdoc666]

whale tail will help w/ hole shot but not porposing shifting weight might

 

[Burger]

Thanks everyone. I'm considering dropping the motor down a notch. I really can't think of way to shift any weight from the rear to the front. It porpoises when I get it trim up on pad to run faster. When I trim it down to stop it I'm only running around 29mph. I had a buddy sit on the front deck once and that still didn't help. Oh well at least she still gets me around good.

 

[Jerry]

I have an old Tracker (1989, fiberglass) bass boat and recently put a Honda on it replacing the original 150 Johnson. The new motor weighs quiet a bit more than the old one plus I have two extra trolling batteries in the back. So, I had the same problem. Couldn't trim it enough to get the porpoising to stop, same speeds as you 30-35. I bought a hydrofoil from Cabela's. (Bass Pro also has them.) Problem solved for about $55. In fact, the boat handles great now. Better than before.