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Author Topic:   Motor Mounting Height
assaf posted 06-06-2004 04:25 PM ET (US)   Profile for assaf   Send Email to assaf  
I have [an Outrage 17 II] with a Mercury 150 EFI mounted on the third hole (middle). The boat has a tendancy to porpoise as soon as I try to trim a bit up. Is this the right hole to mount this kind of engine (V6 XL) to this boat? Thanks.
jimh posted 06-07-2004 08:45 AM ET (US)     Profile for jimh  Send Email to jimh     
Is there really a set of five holes for height adjustment on that engine?
assaf posted 06-07-2004 04:09 PM ET (US)     Profile for assaf  Send Email to assaf     
JIMH , for a second you got me comfused. yes , the engine 1999 150 efi xl has 5 holes of height ajustment. maybe someone that has this kind of rigging on the outrage 17 II can give his opinion. thanks
JohnJ80 posted 06-07-2004 04:46 PM ET (US)     Profile for JohnJ80  Send Email to JohnJ80     

especially the last several messages.

Specifically, there is no 'right' height for any particular boat because the causes are complex.

However, experience seems to show that significant porpoising on a number of whaler hulls can be dimished by raising the motor. Most seem to experience this working best at either the top hole or the one below it (in terms of motor position - higher is better). This equates to roughly 1-1.5" for AV plate above bottom of hull.

Caveats: When up, make sure that you don't have a lot of prop blowout in turns (you shouldn't) and that you maintain cooling water peeing out of the motor (also should be ok).

Make sure that you test the boat the way you use it - loaded with people and gear as you normally would.

Also, no matter what, you will still be able to make any boat porpoise if you remove enough damping, i.e. it is possible to configure the boat in a manner that is ridiculous and see porpoising. For example 100% up trim at 25-30mph will probably cause you problems and you will be excessively bow high.

You should be able to have more trim range than what you describe, if I understand you correctly.


assaf posted 08-08-2004 03:06 PM ET (US)     Profile for assaf  Send Email to assaf     
I took the boat out of the water. the AV plate is 1/2" above the bottom of the hull. should I expect any problem by raising one more hole , that would give 1.25" above the bottom? I have the Laser II prop installed. thanks asaf
JohnJ80 posted 08-08-2004 05:46 PM ET (US)     Profile for JohnJ80  Send Email to JohnJ80     
One hole up can make a huge difference. Whaler recommends 0-3/4" above bottom of hull for AV plate - sounds simple enough to measure, but with the motor trim angle etc it is not as easy at it sounds.

The best way to do it is to raise the motor and try it out. If that works, go up again. Personally, if the motor will still have cooling water, I would be inclined to go all the way up and then bring it down.

You can do this with your trailer and a floor jack. Search this forum and you find directions.

Usually this helps porpoising, if not then the next step is a fin or trim tabs. I personally favor tabs and I bet they would be terrific on that boat.


assaf posted 08-09-2004 09:56 AM ET (US)     Profile for assaf  Send Email to assaf     
I have bennet trim tabs installed on the boat, which helps to stop porpoising, but I have to use them most of the time. where can I look for the method of the floor jack? thanks.
JohnJ80 posted 08-09-2004 09:54 PM ET (US)     Profile for JohnJ80  Send Email to JohnJ80

this worked well for me, YMMV.


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