Stainless Steel Prop - Johnson 1977 70 HP

[johnjsa]

Considering getting a stainless prop for my motor, options are 13 1/4 by 17, 13 3/4 by 15, 13 by 19, 12 3/4 by 21 & 12 3/4 by 23. My motor currently has a 13 1/4 by 17 aluminum, what would your recommendation be as to size, pitch & prop model.

 

[walleyehed]

Re: Stainless Steel Prop - Johnson 1977 70 HP

Let's start with what is your WOT RPM now????<br />What kind of boat are we running??

 

[johnjsa]

Re: Stainless Steel Prop - Johnson 1977 70 HP

I have a 15 1/2 Bomber Bassmaster 1982 model. WOT on my tach is 6000 rpm, not sure if the tach is reading correctly or not. I also have a CMC tilt/trim unit on boat.

 

[willamettejeff]

Re: Stainless Steel Prop - Johnson 1977 70 HP

Also need to know if current prop is cupped or not. I have been very happy with a 13 3/4 by 15 cupped/ventilated prop on my 1978 70hp Johnson on my 14' fiberglass runabout. Wot rpms is just over 5800, quick out of the hole and great accelleration at all speeds and trim angles. Your results may vary.

 

[willamettejeff]

Re: Stainless Steel Prop - Johnson 1977 70 HP

Just seeing your second post John. Your wot rpms tell me your running a standard uncupped propeller as I received the same results on my motor. If you go to a stainless prop that will more than likely be cupped, I believe you'll need to go down 2 sizes to maintain the same wot rpms. So a 15" instead of 17" prop.

 

[johnjsa]

Re: Stainless Steel Prop - Johnson 1977 70 HP

Not sure about the current prop whether it is cupped ot not, bought the outfir used. Whose stainless prop are you using?

 

[walleyehed]

Re: Stainless Steel Prop - Johnson 1977 70 HP

I doubt it's un-cupped...not too many of those around anymore.<br />Let's get a part number off that prop and we'll go from there...even if it is uncupped, we still want a 17 cupped, BUT before we do that, where is the the engine mounted on the transom?? as in what holes are being used, ie, all the way down or is it lifted up some????

 

[willamettejeff]

Re: Stainless Steel Prop - Johnson 1977 70 HP

Actually Kenny, the prop that was on my motor when I purchased it last year was uncupped and brand new. The guy I bought the boat from had just purchased it. I got rid of it because it ventilated like crazy in a turn even with the engine trimmed way down.<br /><br />John, I run both Turningpoint Express stainless and Turningpoint Hustler aluminum props. Both come with a lot of technology for the price, IMHO anyway. You can of course get a higher performance prop, but you'll pay dearly for only a small improvement.<br /><br />Kenny has a lot of experience and will no doubt have some excellent suggestions and advice for you.

 

[JB]

Re: Stainless Steel Prop - Johnson 1977 70 HP

Moving to the new Props forum.

 

[johnjsa]

Re: Stainless Steel Prop - Johnson 1977 70 HP

I am going to take a pic of the motor/CMC setup & try to get you a part # on the prop I currently have. As far as the holes, it is high as it can get on the CMC which sets the motor up & back & I have 1 more hole I can raise the motor up on the CMC plate. The pic should show you, this gets the cavitation plate about 2 inches above the bottom of the keel. Thanks for your help.

 

[walleyehed]

Re: Stainless Steel Prop - Johnson 1977 70 HP

williamettejeff, I guess there are still afew around...most of the OMC built ones are gone (I hope)and MWC has continued on with only the cupped version for this application (13 spline), and I suppose there could be some of there old stock out there on a shelf yet...but remember this, if we have power trim, we stay with the same pitch, even though it's cupped, and in some cases, if a guy has a little time to listen and try some of these things like lifting the engine as far as the prop will allow, we can them go to a higher tech prop and gain even more.<br />Even though we start with a 17 uncupped, we may end-up with a 19 cupped at even higher RPM...this is where things start to really get efficient, and the person experimenting usually ends up saying "Man...I wish I had done this along time ago"....

 

[ob15]

Re: Stainless Steel Prop - Johnson 1977 70 HP

walleyehed, you sure got that right. I'm in the middle of it right now. Will probably add a post about it later tonight.