Need help with prop selection (Force 125)

[BWSmith]

I recently had the stainless prop stolen off my motor and am looking for a new one. I bought it used (it's on an '89 Bayliner Capri 1700) and am unable to locate a plate indicating the year of manufacture. The model indicated on the label specifying operating RPM also states that it's a model 1251X7A. I have looked at some of the various online selection sites and have and they appear to recommend a diameter of 13.5". This is where I need extra insight.

I am asked by these sites if it's a single or dual exhaust. I am guessing a single exhaust as it appears to exit a single outlet shaped like a fin below the antiventilation plate. The available pitches seem to be 15", 17", and 19". I use the boat for mainly fishing and motoring around charleston harbor, if that helps. Beyond this, I am not sure which one to get. Though I liked the stainless one I had, I'm not ready to spend two or three hundred to replace it, and I'm not sure, aside from rigidity, why they are much better than aluminum or composite for my purposes.

Thank you in advance for your assistance and enlightenment.

Bryan

 

[Frank Acampora]

Re: Need help with prop selection (Force 125)

You should look on ebay for an aluminum prop in decent condition for a reasonable cost. Start with a 17 pitch prop and see what the performance is. If the engine runs at the recommended range with that prop, then you are ok and perhaps may consider a stainless prop in the same size.

If RPM is too high, then try a 19 pitch prop and if too low, try a 15 pitch. in either case, you will not have invested much in the used prop so it won't hurt you financially to save it as a spare.

If you look on ebay, any prop that fits a late Chrysler (1980 or later) 75 through 140 or any Force (at least through 1990) 75 through 150 will fit your engine, provided it is a single exhaust model. Open hub props to fit dual exhaust models will fit and function equally well on single exhaust, however, closed hub props for single exhaust -while they will fit--will cause excess backpressure of the exhaust. If you don't mind looking and comparing, SOME Mercury 15 spline props will also fit. They MUST be for the small diameter gearcase--4 or 4 1/4 inch diameter, I forget exactly. And Mercury makes a Vengeance prop in 18 pitch that will also fit. BUT, you are looking at big bucks there.

Since your original prop was stolen, be certain that the thrust washer is still on the prop shaft. if it is not, you will need to buy one in addition to the prop. The same thrust washer fits all props. You will also need either a flare washer (black plastic anti-cavitation washer) or a spacer to fit under the prop nut. This keeps the prop from sliding forward and backward about 3/16 inch with the prop nut fully tight.

You indeed most probably have a single exhaust engine since the dual exhaust models were not as common. Unfortunately, both models used the same exhaust snout. Easy way to tell the difference is to look at the water pick-up holes: Single exhaust engines will have four slots on either side of the gearcase torpedo just ahead of the prop. Dual exhaust will have vertical holes above the gearcase running up toward the cavitation plate, on either side of the leg.

See my private message to you.