New guy with a prop question

[garbonzo06]

I have a 1990 maxum with a 50hp Force engine. Lost my prop last week and am looking for a replacement. I think I have the diameter at 10 3/8th but am torn with the pitch. 11 1/2, 12 1/2, 13??? Any suggestions? I'm only trying to get around to do some fishing. Not trying to pull anything.

Thanks in advance.

[seapuppy]

welcome to the zoo....this is kinda hard to answer since 1) I don't know what your wot is supposed to be and 2) don't know what prop you had in the beginning....so...you need to find out what your max rpm at wot is supposed to be...this is gonna be some experimentation involved since your going to try a prop..run it wot..and then adjust either up or down in pitch size...

keep us informed...

SP

[garbonzo06]

Seapuppy,

Thanks for the insight. I'm a little embarrassed but I have no idea how to check either of those. If I throw a prop on with a pitch that is too high what risk am I running? I'm not looking for a the smoothest ride possible but just something that is going to work and not ruin the engine. Any advice on how to check the RPM and WOT and any suggestions on what pitch I should start with? Thank again.

[seapuppy]

well....I don't think you can ruin the engine with say a too high of a pitched prop...what will happen is that it will take longer to plane if at all....basically concider you pushing your boat up hill in 4th gear.....too low pitch and you'll be screaming and pop up on plane ..yet top speed will be something less than optimum........
so..to check wot rpm..do you have a tach???..your going to need a tach to check rpms.....your owners manual will have the correct info on what the wide open throttle rpms should be running at......

to check the prop pitch....check the hub..it's usually printed on the hub of the prop somewhere.......

might wanna swing by a prop shop and tell them what you have..they can usually recommend something to start with......


SP

[shrew]

SP is on to it. I'd start with the getting the info. suggested:
1) Max RPM Range fro your motor.
2) Diameter and pitch of current prop.
3) Current Wide Open Throttle (WOT) RPM with current setup.

Now compare current Max RPM to Max. RPM range of manufacturer.

If your Current Max RPM is below the Max. RPM Range of the motor, you can go down in pitch. If the current Max RPM of the motor is above the Max RPM Range of the motor, then you can go up in pitch. You will be limited to the amount of size in diameter that you can change. A good propr shop should be able to help. There are also a lot of prop calculators out there.

You say you want to go fishing. That can be done in a canoe......with a paddle. What are you actually trying to achieve? Better hole shot (time to get on plane)? faster top speed? better fuel efficiency?

[CountryME]

Please clarify "lost my prop" . Is it gone or damaged? Most props have stamped part #s. You could bring the part # to a prop shop and match it. If gone, for comparison my dad's 120 force on a 1994 1700 had a 19 pitch prop to keep from over revving it.

[shrew]

Originally Posted by CountryME

Please clarify "lost my prop" . Is it gone or damaged?

Hmmm, I missed that one. Well then my reply makes absolutely NO SENSE. Let me se if we can dig some info. on that OB model.

[shrew]

I believe that the original part number on the Force 50 prop is A293265. I believe this is a 12.5 pitch. Unsure of the diameter, but believe it is somewhere between 11" and 13". To my knowledge there was only one prop for that model, so if you go by the part number you should be all set. Take a look around and use that part number. LEt us know if you have any questions or problems.

[tglee]

I believe that the original part number on the Force 50 prop is A293265. I believe this is a 12.5 pitch.

This is correct. 10 3/8" X 12.5" was the original.

You can change to 13.5" pitch for a higher top speed or a 10" pitch for better acceleration. I'm not sure of what the max RPMs at WOT should be.

The 1982-1994 models were different then the newer ones. 1995 and forward have a max of 5250. The older ones may have been as high as 5500, you need to find out for sure. The rule of thumb is 300-400 RPM difference when changing 2" on the pitch.