Motor Height +/-?

[glass from the past]

OK guys,<br />I have been searching old posts trying to get a good idea for what the proper engine height should be in relation to the cavitation (someone correct me as to the proper term)plate and the bottom of the hull. As per any topic there are as many opinions on this as say synthetic oil . The general consensus seems to be that the the cav. plate should be level with the bottom of the hull. My specifics are this:<br /><br /> My cav. plate sits about 2 inches below the bottom of the "pad" on my hull. <br />My boat is fiberglass, I want to keep the number of holes in the transom to a minimum. <br />It does not have a jack plate, or power trim / tilt<br />I am running a 45 horse Chrysler on a 1979 Chrysler cathedral hull runabout.<br />I have a doelfin on the cav plate now. I was going to upgrade to smart tabs, but spent the money on a new trolling motor instead. So I can't buy any new hardware at this point (next season?).<br />I am in the neighborhood of around 800lbs. on the water. <br /><br />Will raising my motor 2"(or more?) make a difference that is noticable? Am I better off leaving the setup as the manufacturer intended it to be (am I opening a new can of worms, drilling holes in the transom)?

 

[Chinewalker]

Re: Motor Height +/-?

I think you will notice a small, but not insignificant difference. Right now you're dragging the lower unit AND that Doel Fin through the water at all times. Those bolt-on fins work best when they're mostly out of the water at speed. Running them completely submerged all the time can lead to some handling quirks - some of which can be quite disconcerting.<br /><br />Go up!! Your motor has thumb-screws, in addition to the bolts, so you can give it a try first before committing to it. Just make sure the motor is clamped down good before heading out on your test runs. Go up incrementally using paint stir sticks or cheapie yard stocks chopped up into 1-foot lengths. Go until one of three things happens - you run out of transom, you run out of cooling water, or you can't plane off or hold power without ventilating the prop. Try it both solo and with a load. The up side of all this is you "have" to spend an afternoon driving the boat around. Borrow a shop tach, and a GPS if you don't have a tach or speedometer gauge in the boat.<br /><br />- Scott

 

[glass from the past]

Re: Motor Height +/-?

Hey thanks for the reply Chinewalker,<br /><br />I have been debating doing this off and on, but I do have a lake close to my house (1/2 mile) so I can do some tinkering with this. What you say makes sense, especially the handling aspect. Sometimes the boat does feel like it is "glued down" and when I power into a turn, I sort of "pop" out of the water it feels like, so maybe getting that fin outta of the water would be best (and safest)in the long run after all.<br /> <br />

you "have" to spend an afternoon driving the boat around.

Nice

 

[DS-3]

Re: Motor Height +/-?

Level with the bottom of the hull + - 3/4". Drill at least the lower set of bolt holes for test. I can tell you if you have a clamp on motor come off the transom you learn pretty quick about bolting them on!

 

[JB]

Re: Motor Height +/-?

Howdy, GFTP.<br /><br />The correct term is "Anti-ventilation plate", or AV plate.<br /><br />Not a big deal. Most guys understand what you mean if you call it a cav. plate.