hydra-sports question

[xp150]

I have a 1985 18ft Hydra-sports VL475T with a 1989 Evenrude XP150 motor, a SS 14.5 x 24 prop<br />and a reed jack plate. The front of the boat jumps up and down in rough water or calm water unless you are running WOT.In calm water if you trim it way down you can get it to settle down about 35mph. The scale on the jack plate was set on 3" and I dropped the motor down an 1" to 2" on the scale and it helped some but I lost abouit 4mph (down to 56mph).I hope this is enough info and I'm greatful for any help. Thanks for reading

 

[Bob_VT]

Re: hydra-sports question

It is just a problem of weight distribution and trim angle. Try moving some weight up front to stop the bouncing.<br /><br />Bob

 

[DJ]

Re: hydra-sports question

XP150,<br /><br />Typically, porpoising is caused by an engine or prop./trim set up that cannot support the weight of the front of the boat at a given power setting.<br />Thus the bow keeps falling off of step.<br /><br />You sort of proved that to yourself when you lowered the jack plate and it helped the situation. At WOT, your engine is giving all the hp. it has and it may hold the bow up.<br /><br />Sometimes a cupped or four blade prop. will hold a better bite on the water and help.<br /><br />It may be that you will have to do some experimenting-most likely starting with different props. You didn't say what rpm's WOT gives you. You may be able to go down in pitch with a highly cupped prop. and not lose MPH.<br /><br />You may also find that a hydraulically adjustable (from helm) jack plate may be the answer.<br /><br />In the meantime, if you have a lot of weight in the front of the boat, that can be moved, try moving some rearward.

 

[xp150]

Re: hydra-sports question

Thanks for the replys, The only weight in the front is a trolling motor and there is really not <br />anywhere to put any weight. The only thing in the back is 2 batteries (and 26 gal gas tank). I have not thought about a 4 blade prop I might could try that. Thanks again

 

[DJ]

Re: hydra-sports question

xp150,<br /><br />What is your top rpm??

 

[paintermn]

Re: hydra-sports question

try a dole-fin (about $30) or some other hydrofoil that installs on the cavitation plate on your motor. If that does not solve the problem I'll buy it from you.(not really)<br /><br />Those things have solved these sorts of problems for me on about five boats, and are the first thing I purchase when I get a new boat.<br /><br />You could also go with trim tabs, but you would have to fork over $300 more.<br /><br />Try the Dole-fin, and if that does not work (it will) then you are only out $30.

 

[xp150]

Re: hydra-sports question

My top rpm is 5500 and about 58 mph by myself and <br /> 5500 and about 55 mph with friend and tackle.The <br />boat(I think)weighs 850 lbs and is made of kevlor. Thanks