asking to much from my boat?

im new to boating and have a question about speed versus torque? I have a 1987 bayliner capri. its a 20 foot closed nose with small cabin. It seats 6 and has a 20 gallon gas tank. it has a force 125 2 stroke outboard engine with a 13 inch diameter prop set on a 16 degree pitch. At wide open im taching 5,100 rpm and traveling 25 mph with a full tank and 1 passenger. When i take people out to ski im able to pull a knee board, double skies, 2 person tube but anyone on a single ski is very tough. you have to stay down longer so long then its a fight to get up. iboats offers 2 other props for my boat, 17 and 19 degree pitch. im wondering if i go up in pitch what do i gain? more speed or more torque to pull out skiers?

Re: asking to much from my boat?

oh also the prop is not stainless steel

Re: asking to much from my boat?

Ayuh,... Props are meassured in Inches, not Degrees...

A 19" prop will Pull Harder than your 21" prop...

Re: asking to much from my boat?

You will gain speed when going up in Pitch but will lsoe some torque, you can add another blade to save some of the torque.

Re: asking to much from my boat?

Forces are usually a little weak when compared to other brands of the same horsepower, but even so, I would think you'd be able to do better than 25MPH with that setup. I'm thinking 30 minimum should be attainable. I hope your boat isn't lugging around a bunch of soaked flotation foam.

Re: asking to much from my boat?

You are asking a lot from your combo to pull out a slalom skier with more than a spotter in the boat.

Going up in pitch will only make matters worse. It will reduce the acceleration and pull needed to pop the skier up.

You are at the middle of the full throttle range for that engine so an increase in pitch will drop RPM by another 400 for a 17 pitch and 800 for a 19 pitch. Both will reduce performance. Unless it is an aftermarket prop, the "16" degree you have on now is really 15 pitch.

If you know someone with one OR if you can test a prop, a 13 X 15 stainless will increase performance a bit..

Also, you need to trim in the engine when first accelerating the skier, then as he pops out, trim out for best speed. Have passengers move as far forward as possible to get the bow down and the boat on plane as fast as possible.

As mentioned above, 25 MPH is just a bit slower that should be expected. Check the hull for excess weight and check the engine to see if it is delivering performance--at a minimum check compression to be certain it is not too low. Go to the Force forum and at the top sticky, read FAQ and see if your engine is synchronized correctly--carbs opening fully, timing fully advanced, etc.

If money is not a factor, go to the auctions and find a 2 to 1 ratio lower unit from a 90 HP engine. Your current ratio is 1.76 to 1 and inhibits the engine's performance with any prop.

You can use any lower unit from 1979 Chrysler through 1990 Force. Just be sure it comes off an engine the same length as yours--that is 20 or 25 inch leg.

Re: asking to much from my boat?

How do you know it is only going 25 ? You cannot rely on a speedometer, they are very inaccurate
especially on older boats. A gps is the best way to really find out.

Re: asking to much from my boat?

75TowerOfPower said:

You will gain speed when going up in Pitch but will lsoe some torque, you can add another blade to save some of the torque.

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Yes, but he's only at 5100 rpm at WOT as it is. That boat is over-propped in it's current condition. If you drop down a little in pitch it will help get the rpm up where it should be, and help you out of the hole as well, and may even get you a few more mph.

For instance, I recently finished rebuilding a 1979 Checkmate, and am still closing in on the best setup. I started out with a 25" pitched prop with my Johnson 200, it was a dog out of the hole and I could only get 55 mph at around 5400 or so rpm's (other owners with the same hull get close to 70 mph). I dropped to a 23" pitch prop of the same brand and got 62 mph at 6000 rpm with no other changes. It's a matter of getting the rpms up to where the engine can make full power.

Re: asking to much from my boat?

Metric: You are comparing apples and oranges when comparing your Checkmate/Johnson to the Bayliner/Force. The Force 125 was a relatively weak engine and you are correct in saying that he will lose performance by going up in pitch.

HOWEVER: He is already (as best as I can tell) at a 15 pitch prop. If he tried a 13 pitch (which I have never seen for that engine, doesn't mean it is not available) Yes, he will gain some acceleration, but he WILL lose top end by a significant amount. And, at 25 MPH (which I believe because I would only expect 30-32, maybe 34 on a really good day, from that combo in peak condition) he can't afford to lose anything. He needs to concentrate on why that engine is only turning a 15 pitch prop at 5100--if it is indeed a 15. He should check a known 15 pitch prop and see what RPM he gets at WOT. Then, if RPM are low he needs to invesigate why.

Re: asking to much from my boat?

Frank Acampora said:

Metric: You are comparing apples and oranges when comparing your Checkmate/Johnson to the Bayliner/Force. The Force 125 was a relatively weak engine and you are correct in saying that he will lose performance by going up in pitch.

HOWEVER: He is already (as best as I can tell) at a 15 pitch prop. If he tried a 13 pitch (which I have never seen for that engine, doesn't mean it is not available) Yes, he will gain some acceleration, but he WILL lose top end by a significant amount. And, at 25 MPH (which I believe because I would only expect 30-32, maybe 34 on a really good day, from that combo in peak condition) he can't afford to lose anything. He needs to concentrate on why that engine is only turning a 15 pitch prop at 5100--if it is indeed a 15. He should check a known 15 pitch prop and see what RPM he gets at WOT. Then, if RPM are low he needs to invesigate why.

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sorry for the late responce, computer had a moment! you guys have given me alot to think about. Frank you are right about my prop, i found the reciept, i bought it from i boats about a year ago and is a 15. My tach is new aswell as my speedo but you guys are right the speedos are not always right. i looked at the sticky in the force section and the sync sounds really easy, much easier then my manual explains and i think i will attempt that first. My engines says 5500 rpm on the decal next to my tilt motor. is that were i need to be at wide open ?

Re: asking to much from my boat?

you need to put a 175 or a 200 on that boat if you want to go fast.

Re: asking to much from my boat?

Your engine is rated 125 at 5000 or 5200 while WOT operating range is 4500-5500RPM 5100 is right in the middle of the operating range at WOT and correct. BUT-- These engines are a bit happier at the top of the range and 5500 would be better. HOWEVER: If you do drop pitch to a 13 (if you can find one) you will lose top speed. You need to see if you can get that 15 pitch prop to turn a bit faster. As written above, you also need to check the hull for excess weight and waterlogging. If the cavitation plate is even or below the vee in the transom, try raising the engine an inch

Re: asking to much from my boat?

hi frank still working on bayliner, im going to do the syn next weekend but had a question. what is the cavitation plate? is that the part of the motor that i put this plastic wing on that helps my boat plane ou easier

Re: asking to much from my boat?

yes

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propco has a 13 in pitch for this motor. i have this on my 125 force, 20 ft maxum cuddy. boat maxs out at 33 mph.

Re: asking to much from my boat?

You need to prop down IMO try a 15" or 13" pitch.