I have a 1648 MV Jon w/jet tunnel and a Yamaha 40/30 o.b. jet (tillar steering). With me, the motor, fuel and battery all in the back 1/3 of the boat I'm pretty stern heavy so I had the builder weld on brackets for trim tab installation w/o having to drill through the transom.
The brackets are just aluminum channel welded horizontally where you'd normally drill through the transom to mount the Nauticus Smart Tabs SX
They work great, the boat jumps on plane no problem without hardly any weight in the bow to counter the stern weight (not so when I have them in the retracted position... I bought this http://www.nauticusinc.com/pr500.htm so I could get them out of the way when they aren't needed/wanted needed). All is good from just putting along to just after coming on plane (about 1/3 throttle)... untill I start opening up the throttle beyond 1/3. Water starts spraying directly up the transom, the spray on the two outboard sides is mostly harmless if not irritating but the stuff that gurgles in between the motor and transom is a nuisance at best and potentially dangerous if a guy weren't paying attention. I had to stop about every 15 minutes and bail 2-4 gallons out. As a stop gap (and because I want one anyway) I'll be adding a bilge pump.
My only theory (hypothesis really) is:
As the tab cylinder is compressed to the point that the tab is parallel to the water it somehow causes the spray by just sort of skimming the surface.
Possible solution- I need to increase the cylinder pressure by moving to another mounting position (it has five mounting positions to vary cylinder pressure. This should keep the tab-end just below surface at full speed, as it is when I currently come on step.
Problem with solution- I may be causing more resistance than is needed to get on step, slowing the boat down a little. That would be acceptable if it works. I could also remove the trim tabs when I'm hauling weight in the bow.
What do you think?