motor height

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retiredff

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I just bought a '92 9.9 merc. From the measurements I have it is a short shaft motor 17". My transom height is 15". So it will sit about 2" lower than it should if you measure from the bottom of the boat to the anti cav plate. Is the 2" to low acceptable or should I shim the motor up some?

The motor is going on a polar kraft 1448 jon. I usually run w/2 adults and gear,but at times just me. Both adults are 180# or so each and the boat dry is 290#, 2 batteries, usual anchors etc.

Tony
 
Your motor is considered a 15" shaft. Typically smaller engines are either 15" or 20" and the actual shaft lengths vary between manufacturers and sometimes year models. To answer your question on adjusting your engine height the answer is no, unless you want to obtain better performance. If this is the case then look at a jack plate for your engine and raise it to where the ventilaton plate is around an inch above the bottom measured with the cavitation plate parallel to the bottom of the boat.
 
Thanks pappy.

would the jack plate REALLY make that much difference? I have NOT tried it "as is" but will when mother nature allows. :(

I do want the best performance I can get.
 
FYI all it took for me to decide i wanted a jack plate was hitting a submerged log that i would have missed had my motor been at the right height. My Cav plate on my 9.9 is about 3-4 inches below the bottom of the boat... when i hit the log it felt like my motor and/or transom was going to rip out! For a mini jack plate your looking at 76 bucks at bps... much less than a repair or replacement on a boat and motor!
 
OK arkansas, I saw the jack plate on bps. I may bite the bullet and just buy it so when the weather permits I can fish rather than trouble shooting my motor issues.
 
Performance wise the jackplate won't make tons of difference, maybe a mile per hour or two the way you will set it up. Nice thing is that you will be going up around 4" give or take so you can run that much shallower. Don't worry about cooling, at the height you are going it will be fine.
Remember to make the cavitation plate parallel with the bottom when making measurements and raising the engine.
 

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