Motor Height, effect on boat?

[BillBill]

Having used inboards most of my boating life, I now have a Skeeter Sl 190 with a Yamaha 150 on the rear. I use it to both pull skiers and fish. Mostly skiers. What is the optimum setting for the motor. What will happen if I move it up???Move it down??? Thanks.<br /><br />PS I'm thinking about adding a jack-plate.

 

[ob]

Re: Motor Height, effect on boat?

First off determine what WOT rpm motor is capable of at present setting.What pitch prop?Raising motor ,depending on where it is now, can improve WOT performance or cause cavitation.Too low and motor will loose rpms and have idle problems.Rule of thumb is the cavitation plate on motor should be roughly flush with bottom of boat.That is a good starting point.Test height performance in tight turn at around 1/2 throttle with light load.Note for any cavitation present.If not you can raise motor one hole at a time and water test until optimal height is achieved.

 

[BillBill]

Re: Motor Height, effect on boat?

The plate is now about 3 inches from the bottom of the v at the rear of the boat. This is how it came from the factory. I will research all of the other information and get back to you. Thanks for your help!!

 

[ob]

Re: Motor Height, effect on boat?

3inches up or down?By flush with bottom I am refering to the mean bottom of hull.Only a water test will confirm optimal placement.

 

[BillBill]

Re: Motor Height, effect on boat?

Sorry, 3 inches up. I am concerned because I seem to get cavitation in just the circumstances you told me to test them in. I probably just need to be happy with what I have. I tried adding a Doel Fin but that increased the cavitation. I had my wife drive the boat at about 1/2 to 3/4 throttle and saw that the plate was about 1 inch above the water level. I get 65 mph out of it at top end, I just want to make sure it is doing right. Will this also make it hard to steer?

 

[Dhadley]

Re: Motor Height, effect on boat?

X dimension (height) largely dependent on the prop / hull combination. The higher the prop / hull technology, the higher the X dimension. The higher the X dimension the less drag. The less drag, the higher the effeceincy.<br /><br />Sounds easy, huh?

 

[BillBill]

Re: Motor Height, effect on boat?

Thanks for the help. I'll go to the lake tomorrow and see where I am exactly and where I need to go.

 

[ob]

Re: Motor Height, effect on boat?

BillBill, If a jack plate is within your investment range you would probably be a good candidate for one with your high performance set-up.While pulling skiers ,sounds like your present setting is just fine,however depending on the amount of cavitation you experience in tight turns ,sounds like you could afford to be 1 hole lower while pleasure boating.The better bite will produce surer steering in tight turns as well.Good luck and happy boating.

 

[BillBill]

Re: Motor Height, effect on boat?

Thanks, OB. Any recommenndations on a jack plate?

 

[Dhadley]

Re: Motor Height, effect on boat?

What brand / style / pitch prop are you using? Whats the max rpm?

 

[BillBill]

Re: Motor Height, effect on boat?

I am at work right now. When I go to the lake tonite, I will have all that info and post it this PM or tomorrow AM. Skeeter SL 190 Yamaha VMax 150, stainless prop. Pitch, no idea i'm still new to this...RPM, I think 5500, I will tell you tonite for sure. Thanks for the help.