porpoising question

[Matt Dingman]

I have a 16foot crestliner with a 70 horse Johnson on it and it runs great. If I give it the beans and get it up on plane, within a couple 2-300 yards it begins bucking in the front in until I back out of it. What causes this? Is it Porpoising? How can it be fixed. there's nothing more aggravating then having all that power in that small of a boat and not being able to use it for more than just short bursts. Any help is greatly appreciated. thanks Matt

 

[JDA]

Re: porpoising question

Is it a john-type ie flat bottom? Do you have tilt/trim? Trimmed up too much? Engine mounted too high? Too much weight in the rear of the boat with none/very little up front?

 

[5150abf]

Re: porpoising question

Sounds like porpoising to me, motor is trimmed to high.

The motor is trying to lift the bow but at a point is to heavy and pushes down, the motor tries to lift the bow ect ect by trimming down a bit you take some bow lift out of it.

Either lower you trim or move your pin down a hole and see how it is then.

 

[tashasdaddy]

Re: porpoising question

agree with 5150. getting some weight out of the stern into the bow will help also.

 

[mdunn]

Re: porpoising question

Smart Tabs. I have a Smoker-Craft 172 that porpoised like a S.O.B. until I put the Smart Tabs on. Crestliner is aluminum isn't it?
Check out the Nauticas web site and/or give John a call.
$130.00 (approx) and I bet you'll think you have a new boat.

I have a 16foot crestliner with a 70 horse Johnson on it and it runs great. If I give it the beans and get it up on plane, within a couple 2-300 yards it begins bucking in the front in until I back out of it. What causes this? Is it Porpoising? How can it be fixed. there's nothing more aggravating then having all that power in that small of a boat and not being able to use it for more than just short bursts. Any help is greatly appreciated. thanks Matt

 

[tashasdaddy]

Re: porpoising question

read this: http://forums.iboats.com/showthread.php?t=267075

 

[Moody Blue]

Re: porpoising question

Agree 100% about the smart tabs.

Had a 14ft whaler style boat set up with the console near the stern and a 40hp Mariner with power trim. A very stern heavy boat that porpoised horribly. Boat launched out of the hole but once on plane the bow started to bounce wildly. No amount of trimming would correct it. Throttling back settled it down but could only cruise at about 2/3 throttle.

Being frugal (cheap) I built my own set of trim tabs and they improved the ride of the boat beyond anything I would have imagined. No more porpoising and increase overall stability.