1987 Force 85 HP - Which Prop to use 15, 17 or 19 pitch?

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PhillyTerp

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My goal is to figure out which pitch on a prop is the best for my boat between 15, 17 an 19.

I am a complete novice to boats having bought a 1987 17 ft Bayliner Capri with a Force 85 HP (model 356X7A) motor last Fall because I wanted a boat, the price was right and the owner babied the boat. Anyhow, I want to get a new prop and everyone I talk to has a differenet opinion. The boat has no tach so I have no idea what the RPM or speed is with a WOT. The tag on the motor say it ranges from 4500 - 5500 RPM. The engine has been rebuilt and the old owner says it should have 90 HP now, if that matters at all. I had the boat on the water in September and it seemed to run fine, but keep in mind with my experience I don't really know what fine is and how a boat should respond.

Two props came with the boat and they are roughly 13" in diameter. The prop that was on the boat only has these numbers on it A623265 and PS623. The spare prop has these two numbers on it A825285 and PS625. In searching the best that I could come up with is that they are Propco props with the PS623 being 13.25 x 17 and the PS625 being 13 x 19, if I am right on these assumptions. My dilemna is that most places I spoke to about props are recommending a 15 pitch prop. Which is the safest route to take. I am fairly certain that 19 is not the answer.


On a side note, if anyone can help me find a Teleflex 53743P Tach so I can add that to my boat, that would be great as well. Being 20 pole makes it tough to get a tach on it.

Thanks
 

stephen825

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Re: 1987 Force 85 HP - Which Prop to use 15, 17 or 19 pitch?

Yes, i have a very nice new Teleflex Tachometer 53743p in my hands here right this moment. I am returning it to a dealer ... where it will sit forever. I will be glad to give you their name and phone.

30 to 35 bucks is the price I believe.

This tach is for a "Force 20 pole" .

Steve
EDIT
 
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Frank Acampora

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Re: 1987 Force 85 HP - Which Prop to use 15, 17 or 19 pitch?

17 pitch is probably the best estimate without a tach. I am almost certain that 15 pitch will be too little and will cost you speed. It would be good for water skiing, but for tubing, the 17 will be correct. For the 85 on a 17 foot boat, 19 pitch will be too high.
 

my1stboat1

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Re: 1987 Force 85 HP - Which Prop to use 15, 17 or 19 pitch?

i have an 1988 16 foot bayliner/trophy Center console.. with an 85 hp force and i run the 13x17 and my engine rpm wot is 5000 5100 and a top speed of 35 mph... My boat planes out well and cruises nice at top speed... the only thing i wanna change is go from aluminum to stainless with the same pitch im not sure it will help or hurt me...
 

jerryjerry05

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Re: 1987 Force 85 HP - Which Prop to use 15, 17 or 19 pitch?

The 17P is what you need till you can put a tach on it.
The 15 won't work!!!
If your boat is set up for a 17 a 19 will cost more to run.About 10-20% more fuel usage.You might go faster but at a cost.
If you want to use stainless and a 17Aluminum is what's needed now. You need a 15p Stainless.
5500rpm is OPTIMUM!! With the correct load:1/2 tank fuel/1-2 people and equipment.
You need a tach.Anything else is using the WAG system(wild *** guess).J
 

jason32038

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May 25, 2009
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Re: 1987 Force 85 HP - Which Prop to use 15, 17 or 19 pitch?

I used to think mine had a 13x19 but I was mistaken. Tinkering around in the shed I see the lonely prop just sitting there on the ground and I just had to check and make sure. Turned out it was a 13 1/8thx15 aluminum. Michigan 072055 is what the number was. 1986 85hp force on a 15' capri bowrider.
 

capri1600

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Re: 1987 Force 85 HP - Which Prop to use 15, 17 or 19 pitch?

I have a Bayliner Capri 1600 project boat with a Force 85. The 17 pitch is common on this boat and will perform well for the type of boating it's aimed at. That is, cruising around and maybe pulling a skier now and then. A 19 pitch will likely be a little too much. I have my 1983 Force 85 on a 1972 Glastron GT-150 right now and changed to the 19 pitch prop since it is smaller, lighter and designed to go fast. It'll do about 41 on it. Expect about 35mph on the Capri with the 17 pitch.

Marty
http://www.martyhammersmith.com
 

NYBo

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Re: 1987 Force 85 HP - Which Prop to use 15, 17 or 19 pitch?

My '88 version of your boat came with a 17.
 

jason32038

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Re: 1987 Force 85 HP - Which Prop to use 15, 17 or 19 pitch?

Philly try a piranha prop. They have a hubb kit for around $80 and each blade is only $20. A prop kit is $139 I think but the good thing is you can get 3 blades of 15 pitch for skiing and you can buy another set of blades for $60 in a different pitch. 15 would be for skiing and towing...17 for a little less acceleration and a bit more speed or 19-21 for higher speeds and less acceleration(good for fishing to get to where you need to go faster). They also have a wizard to calculate what size of prop you should use according to the weight of your boat and equipment and how fast you want it to go eg. skiing,general use and fishing. It told me that if I switched from my 13 1/8x15 to 12 5/8x21 that I could hit 51mph with my 85hp Force. Check it out http://piranha.com/enginelist.php?manufacturer=Force&year=1986&HP=85.0&submit.x=23&submit.y=12
 

jason32038

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Re: 1987 Force 85 HP - Which Prop to use 15, 17 or 19 pitch?

I forgot to add this...15 would not be the best route to take right now since you have no tachometer and you can't tell what rpm you're maxing out at. A 15 pitch might put you higher than your reccomended rpm range with that size of boat. Id go with the 17 until you get some type of tiny tach or a in dash tach installed.
 

pecheux

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Re: 1987 Force 85 HP - Which Prop to use 15, 17 or 19 pitch?

A tachometer is like having a motor doctor on board.
 

Karla45

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Re: 1987 Force 85 HP - Which Prop to use 15, 17 or 19 pitch?

I have a 1989 force 85HP and still have the owners manual. It says that you will get best performance with a 13.5 x 15. I just bought new one and it has worked out well for me. I am able to get to 39mph but probably higher now since i got all of the problems on my boat fixed. I am sure i am over 40mph now.
 

lifemobile

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Re: 1987 Force 85 HP - Which Prop to use 15, 17 or 19 pitch?

I have a 1989 force 85HP and still have the owners manual. It says that you will get best performance with a 13.5 x 15. I just bought new one and it has worked out well for me. I am able to get to 39mph but probably higher now since i got all of the problems on my boat fixed. I am sure i am over 40mph now.

Howdy,

We have a Bayliner Capri 17 or 18' (it's 17.5" to be exact, so not sure if you round up or down) with a 90 HP Force.

Currently, it has a 13x19 prop...and it's absolutely horrible.

Boat runs good, idles good, etc...just doesn't like to go at all.

With just me in it(5'8" and 160 lbs), IF the speedo is correct, I could only get 15-17 mph.(We have no tach).

We were told we needed a different prop, so my question is this. Would going down just 1 size to the 13x17 make a HUGE difference, or a little...or should I trust what this guy said the owner's manual said and go down 2 sizes to the 15?

Just asking how much of a diff. each size makes, in people's opinions. Summer's almost over and the kids wanna do some tubing :)

Thanks in advance for any reply :)
 

Jiggz

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Oct 23, 2009
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You revived an old thread. You will be better off starting a new to get more responses.

But to give you a quick answer to your question, your problem is more on the engine rather than the prop. First, you need to do a compression test on all cylinders. Second, inspect all plugs are firing and there is no misfiring (especially at high speed). Invest in a tach, even a tiny tach will do so you have a reference for RPM. As for measuring speed you can always verify your speedo with a GPS.

If you absolutely can prove there is nothing wrong with the motor, a waterlogged boat can also prevent you from getting on a plane or reaching higher speeds. Or if the motor is not properly trimmed and heavily "plowing". However, if everything is working perfectly, even with an oversized or overpitched prop for this motor can at least reach 20~25 mph at WOT. It might have slow hole shot or getting on a plane (with overpitched prop) but will eventually catch on and reach higher speeds.
 
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lifemobile

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You revived an old thread. You will be better off starting a new to get more responses.

But to give you a quick answer to your question, your problem is more on the engine rather than the prop. First, you need to do a compression test on all cylinders. Second, inspect all plugs are firing and there is no misfiring (especially at high speed). Invest in a tach, even a tiny tach will do so you have a reference for RPM. As for measuring speed you can always verify your speedo with a GPS.

If you absolutely can prove there is nothing wrong with the motor, a waterlogged boat can also prevent you from getting on a plane or reaching higher speeds. Or if the motor is not properly trimmed and heavily "plowing". However, if everything is working perfectly, even with an oversized or overpitched prop for this motor can at least reach 20~25 mph at WOT. It might have slow hole shot or getting on a plane (with overpitched prop) but will eventually catch on and reach higher speeds.


Thanks for your reply...I called a couple marinas here where I live(Montana)...our altitude is 3600 ft.

Both places said I need a 13 x 15...if we went any higher in altitude I'd need a 13 x 13.

The motor revs up just fine in neutral, but won't get any RPM's with this big prop(13x19) and will barely even plane. Both marinas said it's waaaaay too much prop for this motor and that a 13 x 15 will make it seem like a new boat.

I guess you gain approx. 200 RPM for every pitch you go down...so by going down 4 pitches from 19 to 15, should gain 800 RPM, which going by ear as to how the motor sounds should put it just about right.

Thanks again for your time :)
 

Tforgey

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Aug 15, 2016
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I also have the same booat,same motor,it has the 17,top speed with two people no cargo is 35mph
 

Tforgey

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Aug 15, 2016
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Hey guys can someone help me ?I don't understand how to post a new questionn,please help
 
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