Help selecting prop for a 90hp force/17ft Proline

[mitchbuck]

I'd like to get some input on selecting a prop for my 1984 17ft Proline Center Console (~2000lbs) powered by a 1990 90-hp Force outboard. I put this engine on the boat last year and it came off a small, old bayliner so I am not sure if I have the most ideal prop for it. I am only getting about 18-20mph cruise at 4k RPM and WOT of 28mph at <5k RPM. Also, it takes some effort for the boat to get up on plane with 3 people in the boat. According to the markings, it looks like I have a 13.5in x 15 pitch prop, however, the blades are oddly shaped and there is some wear/damage. Any input on selecting a proper prop would be great!

 

[WIMUSKY]

Re: Help selecting prop for a 90hp force/17ft Proline

The prop is toast. The one blade is bent. I haven't crunched the numbers, but I would think a 17p would suit your needs better. A prop selector we need to be used to verify...... If you have access to an undamaged 15p try it and recheck the numbers. With the damaged prop the current numbers don't mean much.......

 

[mitchbuck]

Re: Help selecting prop for a 90hp force/17ft Proline

The prop is toast. The one blade is bent. I haven't crunched the numbers, but I would think a 17p would suit your needs better. A prop selector we need to be used to verify......

Thanks for the input. What's a prop selector?

 

[WIMUSKY]

Re: Help selecting prop for a 90hp force/17ft Proline

I believe guys are using this one:
Prop Selector | Mercury Marine

I've used it, but it doesn't like my motor/boat combination...

I had updated my post, if you have access to an undamaged 15p try it and report the numbers... A 90hp should spin a 15 greater than 5k.....

 

[Frank Acampora]

Re: Help selecting prop for a 90hp force/17ft Proline

Mitch: before playing with props, check your engine. At the very least, check compression on all three cylinders. Check that the carbs are opening fully: Your numbers are just way too low for a healthy Force 90, even pushing a heavy hull. As stated above, It would be expected to turn a17 pitch prop at 5000RPM.

That is the shape of a standard stock Force prop. AND, from what I can see in the photo, the prop is repairable. There doesn't appear to be too much damage to the blades and the bend can be hammered out if done slowly. Tap a little more than gently using end grain 2 X 4 as an anvil. work from the outside in. If you try to do it fast, it will crack and break off.

Go back to the Force forum and watch the videos at the top Read the synchronizing sticky.

 

[WIMUSKY]

Re: Help selecting prop for a 90hp force/17ft Proline

I agree with Frank. Checking the compression of the engine is simple and quick, providing you have tester, and can be done at home. You can quickly have an idea what the condition of your engine is, you're basically looking for the cylinders to have an equal reading(within 10%). If one cylinder is significantly lower than the others, that cylinder would be bad.

I would think the bent blade on your current prop would skew your numbers that you provided, which wouldn't give a good baseline. That's why a known good prop, whether it's a 15 or 17p, would give you exactly what your speed(a GPS should be used) and rpms really are and establish a solid baseline........

Just to be clear, no-one is telling you to go out and buy a new prop, at least not yet.......