Well you now know that porpoising is not caused by just one thing. It can be a combo of things. They first should be making sure the hull is blueprint flat in the planing area. Any convex or concave can cause porpoising. You should be able to lay a stright edge on the hull (foreward and aft) and it should be dead straight.
Check your weight distribution, check your set back, check the height of the motor on the transom. Do you have a jack plate? Can you raise and lower the engine? A study done by Mercury (I think it was mercury, sorry if I got it wrong) showed that a lot of porpoising is due to slack in the steering system. There should be no slack at all. I honestly don't think it is your prop, but it could be. If all else fails try that.
Back to weight distribution. Where is your fuel tank? If it is low in the boat, amidships or near the stern it's probably ok, but if you have a bow tank it might not be. As you use gas the tank weighs less and changes your center of gravity which changes the center of force on the hull when at speed.
ANyway. keep trying untill you hit it.
Oh yeah I forgot trim. Trim can have a serious effect on porpoising. Try various trim angles.
... Prop is too small and need a bigger prop. Jack up, Jack down.
I guess it is just going to be trial and error.
Be careful with a bigger prop. If you're close to 5000 RPM now, going larger is going to lug your engine even more and 2 strokes tend to consume pistons when they lug too much.
What Ike said about the bottom being straight is right on. A hook can cause a porpoise.
Loose steering will cause a chine walk, not a porpoise.
LetÂ’s see some pics of the boat. Is it a mod VP? Does it have real tunnels and sponsons? What year is it and the motor? The more information you give, the better the advice. I am no set up guru, but I have set all my boats up, granted it took a several tests to get it right.
Oh yea, do you really drive one of those red tractors? If so, I know the problem. You have a SCREW loose between the steering wheel and the seat!!!:jawdrop:
Ike,
My setup is described in the post above yours. Both my gas tank and battery are in the back as they were install by the manufacturer. I do have a jack plate as mentioned in an earlier post. I have also moved the engine up...1" but have not tested that yet.
I have dual cable steering and it is as tight as a drum....I agree with FC, as I don't think loose steering would have anything to do with Porpoise...chine walking maybe.
It is a Stratos Tunnel VEE......I am not sure was a Mod VP looks like, but my boat rides on 3 points....a center pad like a standard V-hull and 2 sponsons like a tunnell hull. I will try and get some pictures to better describe.
Hey Crazy.....What's wrong with my tractor? Do you even know what kind of tractor that is and how much it cost? I have 5 of them. But I don't drive them.
Put a long straight edge on the running surfaces and check to see if they are straight.
Yea, it is a RED tractor--- IHCase, Case NH, or what every they call themselves now. And I guess that depends on how many hrs and what size. I never buy them new.... just try to buy a low hours and good shape. I am looking at getting a 8410 maybe this fall or maybe a Challenger. So yes, I know how much they cost!
BTW I do drive mine, and green is the shizzznit!
Put a long straight edge on the running surfaces and check to see if they are straight.
Yea, it is a RED tractor--- IHCase, Case NH, or what every they call themselves now. And I guess that depends on how many hrs and what size. I never buy them new.... just try to buy a low hours and good shape. I am looking at getting a 8410 maybe this fall or maybe a Challenger. So yes, I know how much they cost!
BTW I do drive mine, and green is the shizzznit!
MASSEY FERGUSON!!!!
MASSEY FERGUSON!!!!
AKA MF. And we all know what that stands for !!!!
If you have a water preasure gauge keep an eye on it as you raise the motor if not I suggest you get one and raise the motor 1/2" at a time until you see the water preasure fall off slightly then lower it 1"
different props react differently try some of your buddys maybe a 24 I personnaly like a chopper but thats me then there is cup rake diameter so much but I think your problem is the prop but again thats my opinion.
I talked with a perfomance propellor shop and they suggested I try a 23 pitch 4 blade prop and raise the jack plate some more....do you guys think this will help?
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