Older 9.8 merc mounting height

[tacx]

Hi All,
I have a 1970 9.8 hp 110 that is on my 12 foot Myers aluminum boat. With the motor sitting down on the transom, the cavitation (or ventilation) plate is about 2 inches below the bottom of the boat. I would like to raise it up so the cav plate is level with the bottom of the boat. From what I have gathered that is the optimum height. But, I am concerned about the water intake getting enough water at that height. The reason is, that motors water pickup is flush on the bottom of the cav plate. Not like some motors that have their pickups down lower on the side of the lower unit just BELOW the cav plate.

So, my question is. If the cav plate is level with the bottom of the boat then so is the water pickup. Will the pickup get enough water?

I know I will be able to tell if I am not getting any tell tale pee stream when running, but I thought maybe some of you experts would know.

Thanks
Tom

 

[merc850]

If you set it with the cav plate level on the water while underway it could cavitate on turns, I would set it slightly below the surface.

 

[jimmbo]

At the speeds you will get with a 9.8 on a 12 ft boat, an inch or two below the bottom of the boat isn't going to matter much. you might lose 1/8 mph.

Your engine does have a water pisser on the bottom of the cowl pan, starboard side. if it is not peeing, it is either plugged, the hose unhooked from the block, or the water pump isn't doing its job.

 

[RCO]

The lower units on those are thin enough where you won't notice a difference. I have a 69 long shaft I have run on my 12' boat that has a short transom. It will still do 23 mph on GPS.

 

[Scott Danforth]

if it still is bothering you, throw a piece of 2x2 under the clamp. this will raise the motor 1-1/2" and it will still be low enough to get water (because you wont be moving fast enough to mater)

 

[tacx]

OK ,guys, thanks for the responces. I will experiment with it and see if it makes a difference.