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Author Topic:   Engine Mounting Height

Smallfrye posted 07-22-2004 02:19 PM ET (US)
What is the proper location of an outboard motor's lower unit with respect to the water while running on plane?
How critical is this setting?
Will 1/2-inch make a difference?
jimh posted 07-22-2004 08:06 PM ET (US)
[Changed TOPIC; was "Outboard performance." Limited scope of the inquiry to a more managible portion.]
Clark Roberts posted 07-23-2004 08:02 AM ET (US)
Ideal height is hard to define but anti-cavitation plate (the flat surface directly above prop) should be even with to maybe 2" above the keel. Testing will determine what height is best and generally is the height that allows full throttle acceleration and fairly hard turns without loosing prop traction (breaking loose). Also maintaining cooling water flow/press is very, very important. Will 1/2 inch make a difference, you bet. Juat try to hold your open hand in the water at 30 mph and realize that 1/2 inch will reduce lower unit resistance by maybe that much and you can see how much force (ma) is involved. A boat with engine at max height will outperform (in speed and economy) same rig with engine all way down and also will ride and "feel" better. Good Luck and happy Whalin'... Clark
PS>now jack/set-back plates are another whold subject...
JohnJ80 posted 07-23-2004 08:42 AM ET (US)
1/2" will can make a huge difference. In general, you want to mount your motor as high as you can without having the prop blow out in turns or in chop.
Whaler in general recommends that you mount your motor with the AV plate 0-3/4" above the bottom of the hull. Experience seems to indicate from those on this forum that this is better if you are 3/4" to 1.5" above the same spot.
I have my motor mounted all the way up and the ride was much improved as was the performance. The dealer had mounted it all the way down when I repowered and I hated it so bad I almost gave it back. Moving it up each hole had a dramatic effect on porpoising, ride quality, economy and trim range.
Searth this forum for engine height or motor height and you will find a ton of discussion on this topic. One of the favorites.
J

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Author	Topic: Engine Mounting Height
Smallfrye	posted 07-22-2004 02:19 PM ET (US) What is the proper location of an outboard motor's lower unit with respect to the water while running on plane? How critical is this setting? Will 1/2-inch make a difference?
jimh	posted 07-22-2004 08:06 PM ET (US) [Changed TOPIC; was "Outboard performance." Limited scope of the inquiry to a more managible portion.]
Clark Roberts	posted 07-23-2004 08:02 AM ET (US) Ideal height is hard to define but anti-cavitation plate (the flat surface directly above prop) should be even with to maybe 2" above the keel. Testing will determine what height is best and generally is the height that allows full throttle acceleration and fairly hard turns without loosing prop traction (breaking loose). Also maintaining cooling water flow/press is very, very important. Will 1/2 inch make a difference, you bet. Juat try to hold your open hand in the water at 30 mph and realize that 1/2 inch will reduce lower unit resistance by maybe that much and you can see how much force (ma) is involved. A boat with engine at max height will outperform (in speed and economy) same rig with engine all way down and also will ride and "feel" better. Good Luck and happy Whalin'... Clark PS>now jack/set-back plates are another whold subject...
JohnJ80	posted 07-23-2004 08:42 AM ET (US) 1/2" will can make a huge difference. In general, you want to mount your motor as high as you can without having the prop blow out in turns or in chop. Whaler in general recommends that you mount your motor with the AV plate 0-3/4" above the bottom of the hull. Experience seems to indicate from those on this forum that this is better if you are 3/4" to 1.5" above the same spot. I have my motor mounted all the way up and the ride was much improved as was the performance. The dealer had mounted it all the way down when I repowered and I hated it so bad I almost gave it back. Moving it up each hole had a dramatic effect on porpoising, ride quality, economy and trim range. Searth this forum for engine height or motor height and you will find a ton of discussion on this topic. One of the favorites. J