Speed verses Pitch

[Bass Runner]

What sort of speed should i expect out of 70hp johnson at 5500rpm with a 13X19 pitch raker omc prop pushing a 520lb clean V hull?

 

[Hooty]

Re: Speed verses Pitch

1.87:1 gear ratio and 5% slip = 50mph.<br /><br />c/6<br />Hooty

 

[walleyehed]

Re: Speed verses Pitch

Check that prop...there is no such thing as a 13X19 Raker......

 

[Bass Runner]

Re: Speed verses Pitch

Well I don't know for sure what it is i was going by what a Johnson outboard dealer told me. He checked the pitch and said it was a 13x19 that's all i have to go by there is no mfg or pitch stamped on it just a part no. T44-309 do you know what it is?

 

[walleyehed]

Re: Speed verses Pitch

All Raker's have just that, stamped in the outer hub. As for your P/N, I'm not sure, it may be a turbo...I'll do some looking and get back.<br />All 19" pitch props, or stamped as such, will not give the same results. One particular propshop I know of that specializes in OEM props only, has pulled high-dollar props right out of the box and found (on a 3bld prop) there to be as much as 2 inches difference in pitch between blades on the same prop!!

 

[Bass Runner]

Re: Speed verses Pitch

Originally posted by walleyehed:<br />[QB] All Raker's have just that, stamped in the outer hub. As for your P/N, I'm not sure, it may be a turbo...I'll do some looking and get back.<br /> All i have to go by is the dealer, and there is no size or pitch stamped on it anywhere except the ser. no. if it is a 19 i am consedering going to a 21 or even a 23 on this thing, last time out it ran 59mph at 6100rpm if the gps and tach are right, want to get the rpm down to about 5500 boy the combo of this motor and the light boat is great if i ever get all the bugs out.

 

[Dhadley]

Re: Speed verses Pitch

Hummm...a 70 with a V6 ratio? How cool!

 

[Bass Runner]

Re: Speed verses Pitch

Originally posted by Dhadley:<br /> Hummm...a 70 with a V6 ratio? How cool!

What do you mean a v6 ratio what does that mean mines a half a v6 don't know if its the port or starbord side though

 

[Bass Runner]

Re: Speed verses Pitch

Originally posted by walleyehed:<br /> All Raker's have just that, stamped in the outer hub. As for your P/N, I'm not sure, it may be a turbo...I'll do some looking and get back.<br />All 19" pitch props, or stamped as such, will not give the same results. One particular propshop I know of that specializes in OEM props only, has pulled high-dollar props right out of the box and found (on a 3bld prop) there to be as much as 2 inches difference in pitch between blades on the same prop!!

Did you ever find anything on the part no on my prop? I don't know for sure what pitch it is but im going to have to go to a higher pitch prop don't know what to look for if it's a 19 i'm going to go to a 25 to get the rpm right at wot

 

[walleyehed]

Re: Speed verses Pitch

I' haven't found what prop you have yet....I'm still looking.<br />A 25" pitch would put you at around 4200-4500 RPM "IF" you could get on plane.<br />IF it's a 19" and you're getting 6100, a 21" would put you around 5700.

 

[Bass Runner]

Re: Speed verses Pitch

Guess i better look for a 21" then, if the one i have is infact a 19" but i thought you would only loose about 200rpm going from a 19 to 21, by the way what is the formula for figuring rpm verses pitch= speed?

 

[walleyehed]

Re: Speed verses Pitch

200RPM per INCH.....19 to a 21=400RPM.<br />Can you remove the nut and inspect under the rear washer to make sure there is no other stamping or moldings...?????

 

[Bass Runner]

Re: Speed verses Pitch

I've had it off and it does have a small number on the center of the hub that slides on the shaft inside the rubber bushing that wouldn't help would it, thanks for the info several of the post on here said different or i just didn't understand what they were saying, glad you said something i would have spent a bunch of money to overprop it, if you think that number will help i'll go pull it again i thought it was a part number for the inner hub or bushing.

 

[walleyehed]

Re: Speed verses Pitch

Any number "may" help..

 

[Bass Runner]

Re: Speed verses Pitch

I found some numbers on the inner hub next to the spline shaft it has a 9 next to a M in a square box on the other side of the hub it has a no. looks like 38414 it is stamped real light and hard to read the last two numbers are hard to tell what they are so im kind of guessing on the 14 but the 384 is legible. then on the outside hub next to one of the blades is T44-309 does this help? Also this prop has a cavitation ring on it if that helps.

 

[walleyehed]

Re: Speed verses Pitch

If it has a ring, we know it's OMC, but the 384???.....I'm not finding anything there other than some props for 25-40HP engines.<br />I'm sorry I can't be of more help....

 

[Bass Runner]

Re: Speed verses Pitch

Originally posted by walleyehed:<br /> If it has a ring, we know it's OMC, but the 384???.....I'm not finding anything there other than some props for 25-40HP engines.<br />I'm sorry I can't be of more help....

If it will help i can send you some picures of the prop. if you will post your E-mail address i'll send them to you my webpage site is messed up so i can't post them that way. My e-mail is dcroc84375@aol.com put Prop in the subject line so i will know it is you.

 

[Bass Runner]

Re: Speed verses Pitch

A big thanks to Walleyehed, when it comes to props this man knows his stuff. Also raised the motor 1", will take it to the lake tomorrow and see what happens. I'll let you know.

 

[Bass Runner]

Re: Speed verses Pitch

I don't believe it took the boat out today and after all the work i did on the motor now it won't run over 8 or 10mph wide open, guess ill have to tear the carbs apart again, i'm guessing i got some trash in the high speed jets, the carbs are opening up and the timing is advancing man this is getting old been to the lake 7 times and have yet to get it running right.

 

[Bass Runner]

Re: Speed verses Pitch

I pulled the carbs off and checked them, nothing in the jets and all ports are clean, didn't find any water in the bowls, checked all gas lines and no problem there, putting them back on today and try it, i think i'm looking for a phantom here.