Odd cooling problem, 50hp force

[bass4brains]

I've run into a odd problem with my 89 model 50hp force.(just bought in feb.) When I run it in the lower three slots on the transom tilt, I get good water flow, no over heating, but it pushes the nose down too much i.e. won't plane off. Top speed of 15.2 mph, by g.p.s. large, deep wake looks like a mastercraft wakeboarder except this is only a 15' cobra. If I raise the tilt to the top two slots to get the nose up I get no water flow and over heat quickly. This is without the thermostat, old one was stuck closed, When I blow though the flow tube with my fingers covering the outlet holes on the leg I get bubbles just below the waterline instead of from the water intake where I would think they should come from. Could this be the infamous copper tube I've read about here? I've searched the forum but not found anyone with the same sort of symptions. Oh Yea I've also got to raise this engine on the transom to begin with as the cavatation plate is 2 3/4" below the bottom of the boat with boat and plate level. Any Ideas?

 

[WillyBWright]

Re: Odd cooling problem, 50hp force

That gearcase should hang a little low in the water. The antiventilation plate should run below the surface. I'm guessing a weak water pump. The housing can wear on the top leaving gaps to allow water to slip by rather than pump strongly into the powerhead. If your transom measures 20" or 21", mount the motor all the way down or up one hole. Make sure you're running on both cylinders. If one sparkplug is clean or has drops of water on it, you could have a leaking head gasket. Water getting in extinguishes the flame. That boat should do about 30. Trim angle should be one hole above level with the keel.