Prop question...again! sorry....

Jersey13

Petty Officer 2nd Class
Joined
Mar 18, 2001
Messages
101
If there was some kind of mathematical formula to figure out the perfect all around pitched, raked, diameter, cupped or uncupped size prop using the HP and size/weight/type boar/motor, that would be great...but it seems there isn't and it's specific to each application so....it's my turn to ask the prop question
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sorry. Took my new (used) boat out last night after i slapped the prop from my bass boat on (basically, the first time out with the boat) and it did horribly. Dragged real bad out of the hole (trimmed all the way down and every which way) until finally getting her on plane - 37mph, 3800rpm (tach correct, crossed referenced with meter) I could get it up on the r's a little more by fully trimming out but it didn't increase speed, seemed to slip more and caused the bow to buck like a bronco. This is what's involved:<br /><br />* 86' wellcraft 192 cuddy 19', 170 Mercruiser w/Alpha 1, calls for 42-4600rpm<br /><br />*prop used - SS, can't find a name anywhere, stamped on side = 600 171 9 HO and up near the front edge, hand scribed M25<br /><br />my luck, it's a custom prop and last nights readings are a waste. o'well. I know i could possibly go to my local reputable marina and ask to try out a few props to dial it in but, if i could save $50-75 bucks and not paying more $$$ to the Gov by getting the correct prop over the net, i will. If your a small mom and pop retail shop, sorry. I know this hurts, first hand (sports shop) So, i'd hate to go and ask for help and then after i figure out what i need, turn around and stab him by buying it elsewhere. If it comes down to it, i'll have to pry the $$$ from the bosses (wife) purse and just buy it locally
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Thanks for any help in advance. And if you happen to have 10 different diameter, pitched, raked blahblah props just laying around, please, feel free to send them to me, free of charge.
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Dhadley

Supreme Mariner
Joined
Feb 4, 2001
Messages
16,978
Re: Prop question...again! sorry....

I wouldn't say it was a complete waste. Most likely your bass boat prop is in the 25" pitch range. Hence the M25. Sure it's too much for your Wellcraft but it's a start. My guess would be something in the 19" or 21" range (give or take) depending on the average load and style prop you choose.<br />Get your average load on board and try either. Once you try a brand name prop with a known pitch it'll be easier. Try one that is in good condition and hasn't been rebuilt. If you know your gear ratio we can do some further calculations also.<br /><br />Good luck Jersey!
 

ODDD1

Lieutenant Junior Grade
Joined
Jan 23, 2001
Messages
1,054
Re: Prop question...again! sorry....

Jersey, your gonna spend some money...as usual, hadley is right,{lol} go buy yourself a name brand aluminum 19 pitch prop...will it be perfect? course not! aint a boater here thats perfectly happy with his prop! <br />BUT heres why....you need a base of reference for future prop decisions,and this will do it...the 19 is a best guess, maybe a little on the low side, at worst it will be your spare..DONT BOAT WITHOUT A SPARE!...at best it will be your 'lotsa friends in boat water ski prop'.....have fun!
 

Jersey13

Petty Officer 2nd Class
Joined
Mar 18, 2001
Messages
101
Re: Prop question...again! sorry....

Thanks guys. really appreciate the help. I guess i'll go with either a 19 or 21 aluminum and then once i find what works best, i'll go get an SS in the same size. I think the prop that was origanally on there that i never used (twisted) was a 21 aluminum, but i don't know how it performed because the orig owner passed away. When i re-try with something new, i'll post the results. And i'll get the gear ratio also. Thanks again.<br /><br />-Jersey
 

dougb

Cadet
Joined
Jan 22, 2001
Messages
6
Re: Prop question...again! sorry....

Quite a few years back I owned a 19" runabout with a 470(170hp) Mercruiser, Itworked best with a 19" pitch, 17" if heavily loaded or operating at higher altitudes. I tried a 21" and was not happy. I would spend my money on a 19 and I agree with the others that if it is not exactly what you are looking for, it will be a good spare, or if you are lucky your local dealer/prop shop may have loaners for you to try.
 

Jersey13

Petty Officer 2nd Class
Joined
Mar 18, 2001
Messages
101
Re: Prop question...again! sorry....

Thanks doug. appreciate the info. I'll probably go with the 19p first. That should put me in the 42-4600rpm range. I really dont know what kind of speed i should be getting with this type of boat. I'm used to my bass boat with the 25p - almost 6k rpm @ 58mph. I guess if she does 40mph, i should be happy....as long as she pulls out of the hole ok. Thanks again.<br /><br />-Jersey
 
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