I need advice, please

[383cross]

I just bought what I believe to be a nice little boat, It's a 85 Bayliner Capri that I think came with a 50hp Force engine, but someone has put a 1976 65 hp Mercury on it. The prop from what I can tell is a 15p(numbers are really faded, it's stainless)I keep reading about motor height, cavitation plates, ect. Can someone clear up what the installed height of the motor should be? I'm new to boating so I have no idea what the cavitation plate is so all the boating terms are greek to me right now. I'm actually a drag racer who's getting into boating so the mechanics should be no problem but the names are confusing me. I took the motor to a reputable mechanic who said the motor was in real good shape and should fly (the guy I bought it off of said it ran 36mph with 3 people in the boat). Maybe my idea of flying is really different that everyone else's but I can see this thing even having enough power to pull a skier out of the water. When I open up the throttle the front of the boat lifts waaaaay up but the forward motion isnt very impressive to me, maybe i'm trying to compare to my drag car or something but it doesnt seem to pick up any real speed so i cant see how i can use it to ski with. Also the motor doesnt seem to rpm like I would think it would, everything i read looks like it should run around 4500-5000 rpm, no tach in the boat but if I guage on how it sounds probably about 2500-3000, at this point I really dont want to put a bunch of money in it till I know it's worth keeping but anyone have any simple or low dollar checks? Interested on any input anyone can provide me on this boat.

 

[walleyehed]

Re: I need advice, please

I would suggest you spend the money and install a tach...this is the main and most important gauge in the boat. we have one gear and the only way to make that 1 fwd gear be efficient is to prop it to reach the max RPM with a normal load.
The "cavitation plate" as some call it, is actually the "anti-VENTILATION plate"....the level surface just above the prop...wide at the rear and tappers as it goes fwd into the gearcase/lower unit. This plate helps to keep air induction into the prop to a minumum. This plate is also what we use on a boat like yours, known as a run-about, to determine the right mounting height of the engine for best performance.
The best starting point is to have this plate even with the boat bottom if you were to lay a straight edge down the keel and extend it past the engine, this plate should not be below the line of the straight-edge, it should be even with, or slightly above as a starting point.
Your engine should be propped for around 5500RPM. The only way we can set this up right, is to have a tachometer to know where we are now.
Most boats with no "extra" lifting devices require "about" 3000-3200 to plane-out, and your boat would probably plane out between 16-18mph.
Even if you could get a tiny-tach to verify RPM, we can use those figures to get you pointed in the right direction.
And yes......35mph in this style/size of boat is considered "moving right along"....

 

[steelespike]

Re: I need advice, please

If it came with a 50 it is probably rated for 50 hp.Is it 14 ft?
16ft is rated for 85 hp. There can be legal and safety issues running over your rated hp.Be careful.The small bayliners are known to develope rotted floors and transoms.Take a hold of the motor and push front to back and watch for transom flex.
I believe there are holes in the transom bracket to allow raising the motor.With the boat on the trailer;raise the bow of the boat and carefully set the skeg(fin below the prop)on a block of wood.On most you can CAREFULLY remove the positioning bolt and loosen the other bolt.As you gently raise the bow the motor will slide up.do one hole at a time raising the motor to a point just before ventilation (motor revs prop loses bite) becomes a problem. be sure it pumps water.Depending on your present setup you could gain a couple of mph and a slight improvement in mileage.Your motor will use about 6.5 GPH(gallons per hour)at WOT(wide open throttle)
Does the motor have power trim?Trim in(prop closer to the boat)to improve hole shot.Manual trim set to best all around performance.Let us know how you make out.