Help! with Proper outboard height and trim.

[86vintage]

<HR style="COLOR: #72a5d8" SIZE=1> <!-- / icon and title --><!-- message -->I read about 1* to 2* positive trim. My boat has a jackplate 6' setback and power trim and I needed to jack upward till slight prop slip then back(lower) off then tilt up to get the prop slipping to reach my top speed.
I have tried different jackplate height but last summer was my first year with a jackplate and power trim and I tried 8 different props. I had fun and got the boat to its highest speed. Though there was no clear science, I was just havin fun!
Can someone explain the Prop heights, trim angle and give me a basic description of each and what to start with first?
thanks
James-86vintagehttp://forums.screamandfly.com/forums/images/icons/icon14.gif
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[Dave S]

By jacking it up you reduce the drag on the lower unit. The props rake works better to lift the front of boat up reducing drag. Higher motor hights lessen the prop torque on the boat and you will lessen the chine walking. A higher transome will let you use less trim angle with better results. Time for pressure gage and solid mounts. ;)

[sho305]

The basics are the higher the jack the less drag the LU will have, but you will lose bow lift. You need to have the hull at the right angle of attack to get the best speed and normally you use the trim to bring the bow up to there. The higher the LU the less your trim will work, so that is as far as you can go when you lose lift or you go slower. Different props will react differently, they might have more or less lift, more or less slip, also some work higher and some not.

Kind of sounds like that prop is too much pitch and you are getting more rpms letting it slip (for more power)? The jack helps move the motor weight back also, and you can move other stuff back to get less weight in the bow if you don't have enough lift, and/or get a bigger jack. It is a balancing act and everything you change might change something else. It is nice if you can find someone else on here with the same boat and compare setups. 1-2 degree is good but does not sound like that prop is hooking up quite right. You could be too high or not the right type of prop. Also depends on what kind of hull you have as some like different setups that others.

My checkmate would do that also, but it had no jack. I think it went a hair faster slipping because it got a hair more bow lift (it has heavy bow and that was tons of trim). It was actually running a little too much rpm for max power so it had to be lift.

[86vintage]

Have the water pressure gauge I will be upgrading from 115hp inlines to a 200 hp 2.5. Just got the solid mounts for the 2.5 Have a clean stock low hour fresh water 1995 EFI XRi (kinda stock will install Reeds and a tuner and mill heads) BUT I just bought a complete 1999 2.5 powerhead with a stripped crank splines. The deal came with a good crank. I bought a mid section and race cowl all short cash from ebay over the last three months, Plan on Porting, got 150hp small chamber Heads installing Boyson reeds, bobs tuner and nosecone and Vertex pistons and refresh all bearing needles and seals. So this is why I am asking about set-up because I will setting the boat up with the stock motor get dialed and balanced (Rearset) then drop on the hotrodded motor. I have a feeling I'll be installing a foot throttle control cause I believe I'll be hangin on!!
So I want to learn more about set-up and take notes to make sure I am going in the right direction. I want to do things right cause now things are now getting expensive in comparison to the good ol cheap inlines!
Spring is right around the Corner!
James-86vintagehttp://forums.screamandfly.com/forums/images/icons/icon14.gif

[sho305]

What size/type boat? You will certainly want a good dual cable or hydraulic steering, foot throttle, trim on/near the wheel, and solid mounts unless you have a big slow boat. Changing the power (HP) will also change the setup, but you should be close.

[86vintage]

I have a 1991 Chris Craft 15.5 foot 17 degree V hull alot like an old 13 foot Checkmate I had but a steeper Rise. The boat will be extended by 3 feet and the hull tech will be copied and blended from the Allison and other new style stepped transum designs with a "Pad". I realy like the Allison hull design. I have a few plans but have not finalized the dimensions but I did order 30' feet X 52" inches of carbon fiber and 30' feet X 52" inches of kevlar. and researching all the latest technology of composite design and structures. Fibre Glast Developments Corporation has a nice video and a book called Composite Basics Seventh edition. That walks you threw the new technologieswww.Fibreglast.com there in Ohio. So I am building a light powerfull bullit. Know I need to find out about set-up. I'll be doing searchs in the forums. but tonight is the first I have started to seek knowledge!
James-86Vintagehttp://forums.screamandfly.com/forums/images/icons/icon14.gif

[sho305]

So it will be 18.5'? Are you going to notch the transom? That has about the same effect as setback/a jack. Be careful if you are making a new bottom, you might want to get Jims book or software at aeromarineresearch.com.

[86vintage]

Ya I purchased the book about 6 months aga and Jim Russell Has been very supportive and always willing to give advice - Good person.
I am a Mechanical Engineer for a medical device firm. So I have been doing my home work. But I have not done my homework on Outboard set-up. I really want to build the boat around the motor. I have been following Alen Powers hydrostream project he's doing a great job. I hope to do my project as clean and well thought out as his.
Take care,
James-86vintagehttp://forums.screamandfly.com/forums/images/icons/icon14.gif