2 Props..what to do???

[cordell]

Hello, I bought my motor an 85 horse Force 1987 in year. The motor runs great and pushes my 15 ft Glastron around just fine. Well today I was doing some cleaning and changing LU oil when I decided to swap props. The one on the boat is numbered PS665 it has some chips and chunks in it. The one I want to put on is numbered PS625. I had not noticed they were different until now I had figured on swapping when I had extra time. That time is now and well now I am lost! lol If anybody knows the differance in these and what one my boat needs I would love to know. Who knows I my have 2 props that dont even belong for my setup!
Thanks in advance,

cordell

 

[steelespike]

Re: 2 Props..what to do???

If you have a tach run each prop and check the rpm at wot(wide open throttle)The 85 developes its power at 5,000 rpm wot(wide open throttle)you should not exceed 5,500 nor run below 5,000 at wot.It would be good to also have your speed by gps.This won't tell what props you have but may help determine which has best performance.

 

[cordell]

Re: 2 Props..what to do???

I dont have a tach but did GPS at 31 mph. I went ahead and swapped and will try the other in the morning. I have a littler river 3 miles from the house, not much but it is enough for testing. I have a little trouble getting WOT too. Some might find this funny others will say it is pathetic, lol. I got controls from Johnson rigged to the Force. Everything is good besides the fact there is not enough travel to reach WOT in the throttle cable :[. I am currently searching out some Force (us marine) controls. Thanks for the help.

cordell

 

[steelespike]

Re: 2 Props..what to do???

I did cross the PS625 as a 13 X 19. The 19 may not be enough prop on that 15 footer.Its very important to get the max rpm.

 

[cordell]

Re: 2 Props..what to do???

I would want to go with more pitch then? It does seem when at idle or no wake for a period of time it wants to sort of bog when taking off. The prop I am speaking of is in real bad shape though. If I am supposed to see a difference in props that are 19 and those at 17 , these look dang near the same. On the side of each is stamped 19c and the other is 15c.....

cordell

 

[steelespike]

Re: 2 Props..what to do???

I would want to go with more pitch then? It does seem when at idle or no wake for a period of time it wants to sort of bog when taking off. The prop I am speaking of is in real bad shape though. If I am supposed to see a difference in props that are 19 and those at 17 , these look dang near the same. On the side of each is stamped 19c and the other is 15c.....

cordell

Yes if too much rpm with the 19 you will need more pitch.
Not unusual for a motor to load up a little at no wake speed and sort of shudder a little when first opened up.
I'm guessing 19c is 19" pitch clockwise rotation and 15c is 15" clockwise.
A 15 is most likely too small in your little 15 ft boat.

 

[cordell]

Re: 2 Props..what to do???

Figures I would have the one thats to big and the one thats to small, needing the one in between. I will test the 15c and go from there, if needed I will want to try and use a 17 then if thats the one purchase a SS prop. :]


thanks
cordell

 

[Silvertip]

Re: 2 Props..what to do???

Before you mess with props, get the right controls on the boat so you can get WOT. Without that happening and also without a tach by the way, you will never know which prop is best.

 

[steelespike]

Re: 2 Props..what to do???

Figures I would have the one thats to big and the one thats to small, needing the one in between. I will test the 15c and go from there, if needed I will want to try and use a 17 then if thats the one purchase a SS prop. :]


thanks
cordell

The 19 may be ok but when i said it may not be enough prop i meant you may have to go higher pitch. don't make any changes without your max rpm and speed. guessing at prop size is at best a crap shoot at worst the premature death of your motor.

 

[Frank Acampora]

Re: 2 Props..what to do???

I have almost the same set-up with a 15 foot Glastron V153 and a Chrysler 90. This set-up attains 42-45 mph at wide open throttle with just me in it. The engine likes a 19 pitch prop. 15 pitch is WAY too small but you CAN get away with it if you cup the hell out of it. Problem is cupping lowers the RPM, but speed still suffers because there is just not enough pitch. So, efficiency and gas mileage is poorer.

You can use a 21 pitch. It will lower thr RPM quite a bit--right around the lower RPM range but speed will stay the same because of the higher pitch. Acceleration and hole shot will be worse though. Sometimes I do it but I don't really recommend it for use as the primary prop.

FIRST: get the correct controls and cables on it. You can not jerry-rig it and expect to get proper performance. AND, if you can not get WOT, then there is no way to adequately assess the performance.

You can get the prop repaired at any marina for a reasonable price. Or, you can buy a used one on ebay--they come up all the time. If you want a new one, right here at iboats.

Finally, I have an old style Chrysler/Force 19 pitch Stainless prop. I consider it to be superior to any stock prop out there. If you are interested PM me. But FIRST, Get WOT and see what your speed and RPM are.

 

[cordell]

Re: 2 Props..what to do???

Frank, I have the 156 and well I could not hit wot but did get 31 mph (gps) with myself, wife, and 2 kids (6 and 4) in the boat. I was also on a river with many turns so this top out was done pretty fast. I believe more room would give me more speed. The prop on the boat at that time is the 19 pitch, though the 2 have diff numbers I cant really see a difference with the naked eye. I will try to get a PIC up tomorrow of the prop and let everyone see why I want to change this thing out. It also sounds like a tach is in the near future. I had no idea it was this important to match rpms with the props. I have learned a lot here at this web site!

thanks,
cordell

 

[cordell]

Re: 2 Props..what to do???

I went out today with the prop that has the 15 stamped in it. The prop is in better shape than the 19, anyway here are my findings. Out of the hole I was faster, a good bit faster than the 19 prop. I hit my wot (controls still holding back) and the motor seemed to sound like it was less RPM than with the 19. My top speed was not as fast though. It was not a good test as this little river in my town was flooded with people on kayaks today! I do feel that with the right controls I could have gotten more top speed and raised the rpm a bit. I do have a few leads on some controls and will be purchasing one of the 3 sets today. As for a tach I see where to install on my wiring diagram though I am not sure what type to buy. Autozone tach works, or a special tach is needed for Force 85 horse. I will thread this in force/chrysler to.

thanks,
cordell

 

[Frank Acampora]

Re: 2 Props..what to do???

You need a 20 pole tach specific to Force engines.

V156 is the bow rider version of the 15 footer. Mine is closed bow and I believe yours is also a modified tri-hull whereas mine is a straight Deep Vee. However, on plane, performance is similar.

Smaller boats are more sensitive to loads than larger ones and their speed tends to drop more with the same load. Even so, With the people you were carrying, I would expect to see at least 36 MPH at WOT.

With some props you can see the difference in pitch if you put them on a flat surface next to each other. With others, you can not. Try looking at the blade where it joins the hub. Since the hub length is fixed for a given brand of engine, it will be the same on both props. So will blade area (within reason on same model prop) However, the blade may start higher on the hub and finish lower on the hub (ie. shorter blade length--not really shorter, but "tilted" less) for a lower pitched prop.

 

[jauguston]

Re: 2 Props..what to do???

For about $40.00 you can get a universal Tiny Tach that will work on anything with a spark plug. You wrap a special soft end wire around one sparkplug wire and attach a ground. I use mine for outboards, lawnmower engines and just about anything I want to check RPM. Very handy tool. Google tinytach and get their phone number. Call them and tell them you want the one you can set the number of pulses per revolution.

Everybody should have one (-:

Jim