Cavation

[shvy]

I have a 1989 23' Bayliner Trophy Cuddy 2302 with 125hp force twins, I used the boat for fishing (Salt Water). I get 4500-5000rpm at WOT @29mpr. I did a compression test on boath eng. And got 150psi to 145psi, Check the timing it was OK off about 2 deg + or -, I get good spark on all, but i get cavation on the port side eng. My problem is how do i grt ride of the cavation and go a little faster, my prop's are 13 1/4x17

 

[Frank Acampora]

Re: Cavation

OOOOH! My dream boat! A 21-23 dual outboard cuddy.

The cavitation has nothing to do with the condition of the engines. It has everything to do with placement of engines on the transom and tilt/trim. Since Force engines are not counter-rotation, and since the problem is on the port side, I'll bet you are riding higher on that side and the prop is nearer to the surface. First try different trim on the port engine--not the best fix but cheap and fast. Be sure weight distribution within the hull is letting it ride level. Maybe smart tabs will help.

All the above assume that you do not have anything protruding from the hull bottom in front of the port engine. Anything that causes turbulence or entrains air in front of the engine will result in cavitation.

Since the hull is a deep vee, check to see if the engines are equally spaced from the centerline or keel. If the port engine is an inch or two closer, in effect, it will be riding higher in the water. If that proves ok, AND if you have the room, then try moving both engines outward on the transom about 1-2 inches. In effect, since the transom is shallower as it goes toward the sides of the boat, you will be burying the props a little deeper. If you do move the engines out, it will result in easier docking because of the increased leverage, BUT you will need to sync the engines closer at cruising to track straight.

By the way: I think I remember reading somewhere that the engines should point in toward each other about 1-2 degrees so that the prop washes meet about 2-400 feet away from the boat--probably for straighter tracking.

 

[shvy]

Re: Cavation

I do have a scoop for the bait tank thats protruding from the hull bottom in front of the port engine about 25" from the front of the prop. I all so have on the starboard side a through hull transducer for my sounder in front of the starboard side eng. about 25" from the front of the prop, but the transducer is shape to where the front and rear are a "V'. I check where the cavitation plate sat and they were about 3/4" below the deep V on each engine. (of corse with the engines down). The starboard side has no cavitation at all. Oh I do have trim tabs. I will take out the boat this weekend and try tilt/trim.