Need to select prop for 83 CAPRI - force 85

[mrix]

I don't know much accept this:

1. My prop is a different color than everything else so it had been replaced
2. I don't know what the OEM is supposed to look like/spec
3. It's broke from me driving into the ground and needs to be replaced.

My max speed was 30mph on gps which seemed slow for 85 hp and 1000+300lbs

Thanks
-Mark

 

[mrix]

Re: Need to select prop for 83 CAPRI - force 85

been using this

http://www.rbbi.com/folders/prop/propcalc.htm

im guessing on a few but knowing that i can reach 30mph max will help me determine what my max speed could be

id need to know the max rpm for the 83 FORCE-85, im guessing something between 3000-4500.

My gear ratio is 2:1

 

[mrix]

Re: Need to select prop for 83 CAPRI - force 85

found a number on the existing prop, reads 5546

 

[Mark42]

Re: Need to select prop for 83 CAPRI - force 85

get a 19 pitch prop and you should be in the high 30's low 40's. I run a PS625, its a 13" x19 pitch on my 85hp Capri 1600 Cuddy Cabin and it ran 38mph. If I trim out, I can probably get another 2 or 3 mph.

 

[MWBROWN]

Re: Need to select prop for 83 CAPRI - force 85

I have a 13 x 19 on my 85 hp 1984 fish and ski, Bayliner.
Max rpm for that engine is 5500 rpm.

At 5200 I get about 36 MPH with 500 lbs of people and fulll tank. This is with an aluminum prop.

Hope this helps.

Mike

 

[mrix]

Re: Need to select prop for 83 CAPRI - force 85

Awesome, thanks for the help guys.

i think im looking for a 13.nn x 19

what kind of slip can i be expecting, im guessing its gonna be something between 0.15 and 0.25.

5000 rpm
19 pitch
0.15 slip = 38.2mph
0.25 slip = 33.7mph


5500 rpm
19 pitch
0.15 slip = 42.1mph
0.25 slip = 37.1mph

so it looks like this is what i want.

how much should i expect to pay for a used prop?

 

[Mark42]

Re: Need to select prop for 83 CAPRI - force 85

What boat do you have the 85 on?

 

[mrix]

Re: Need to select prop for 83 CAPRI - force 85

1983 Bayliner Capri.

one guy i talked to yesterday said if i go with a pitch to great i will throw a rod...
i figure hes full of ****, this things gonna explode when it wants with or without a different prop.

 

[Mark42]

Re: Need to select prop for 83 CAPRI - force 85

Capri model came in various lengths from 16 to 20 something. Which one you got?

 

[mrix]

Re: Need to select prop for 83 CAPRI - force 85

smaller one, 16.

i dont have a tilt module either, just a pin.

i think it weight is ~1050lbs

 

[Mark42]

Re: Need to select prop for 83 CAPRI - force 85

I bet you will do 40 or better. Next week I'll be on the bay with my 16 foot Capri cuddy. It weighs a little more than the bow rider models, maybe 100lbs, and maybe a little more wind resistance. But you should do the same or better than I can get. Righ now fully trimmed in it was doing 38, so if I play with the trim pin, I bet I'll get 40-42. Will keep you posted.

 

[mrix]

Re: Need to select prop for 83 CAPRI - force 85

i just discovered that my throttle was only opening up 2/3 of the way!!

now im not sure what i should do. the current prop i have is beat to hell, its going to be hard to tell if the greater pitch is helping me or not with nothing solid to compare it to..

i guess i could straighten it out as best as i can with a hammer and give it a go..

 

[Mark42]

Re: Need to select prop for 83 CAPRI - force 85

Don't be afraid to take a hammer to that aluminum prop. I have cleaned up a few "beaters" and it can make a world of difference. It helps to have a clean prop for comparison, but finding the best blade and studying it's contours also works. Just put in a vice and tap away. Also take file or sanding disk in a drill and smooth off the rough edges. Don't make the leading edge of the blades sharp like a knife, they should be dull and blunt like when new. And if there is a gouge, just fill it with some epoxy and sand smooth. I've filled chunks the size of half a quarter with epoxy and it held up to my 40hp.

Believe me, it will make a prop that is showing its wear back into something that works and doesn't vibrate the heck out of the outboard.

Hint: the trailing edge of the blade on my (non-cupped) OEM props are straight. So if they curve, straighten those suckers out! The vice comes in handy for this.

 

[mrix]

Re: Need to select prop for 83 CAPRI - force 85

unfortunately i lost a piece of it. im going to not grind/sand the broken blade to try to account for it.. the big problem is going to be recreating the contour to what its supposed to be.

 

[MWBROWN]

Re: Need to select prop for 83 CAPRI - force 85

As you asked a while ago. A used on on Ebay, 40 to 60 normally. Good shape. I missed three of them trying to be too cheap. Sometimes they go higher. Half the time they don't know the pitch.

Also, you can send yours to Port City Props (do a shearch on the net)
I had a silver dollar size chunck out of mine and they repaired it, painted it and shipped it to me for about 65 dollars, If I remember right.

Mike

 

[mrix]

Re: Need to select prop for 83 CAPRI - force 85

Well, i got a different prop.

Its a michigan prop, i cant find it on the site.
On the side it has the number Z873, and something else on the other side that i can't make out at all, it reads "1 something something something C"

on the inside, where the thrust bearing goes i can read 'MICHIGAN' 1042 and K591

unfortunately none of those parts of serial numbers match with my prospective propellers.


This prop seems a little bigger, heaver, maybe an fraction of an inch wider. It looks like it was on an engine that put the exhaust through the hub.

The strange thing is that it gets me to the same speed as the original. Actually it little lowered the top end by 1 or 2 mph (at 28 to 29 now) My tach is still on order so i dont know exactly what its doing but the motor doesn't seem to wined up as much as it did before, and strangely it feels like the new prop gives me much better accelloration from zero to 20mph, the boat will take off at a 45 degree angle.

Im starting to think that no matter what way i spin it i still have x amount of HP thats going to get me to x speed. I've tried all 4 positions of the pin (power trim, ha) and it seems to be planing ok. I did a compression check on the engine when i purchased it and all they cylinders where in spec. Could i be suffering from some timing issue or something to that nature? it really only gets the lead out when i put the throttle down past the half way mark (when it starts moving the ignition advance lever)


basically im out of ideas at this point... maybe 30mph is just its max speed?