Prop & setup guys

[Zaxxon II]

Sorry to be such a pest but I'm confused. 17ft Stratos w/150 Johnson: Raised until prop vented then down one hole, original prop alum.15 X17 got 5800rpm at 42mph 16% slip, backup prop alum. 14 1/2 X 23 vented got 5600rpm at 49mph 25% slip, Just tried a SS Turbo 14 1/4 X 20 this weekend and got 6000rpm at 48mph for 21% slip. All speeds were gps the water was choppy when I tried the SS Turbo and could have gotten a little more out of it but ran out of water. Two people and a full load of gear for all. Motor runs great, has a great hole shot with all props although the 17 is best. Any opinions on the high percent of slip and what I think is slow speed for this boat, and is it alright to run 6000 at WOT.

 

[walleyehed]

Re: Prop & setup guys

The Turbo has had som pitch removed, I would guess..as the slip numbers don't indicate a Turbo in factory form.<br />I can say, however, the 391200, 15X17 for some reason, is a fast prop...my data shows this particular prop to be fast with good RPM...I can't say why though...in fact, this 391200 is faster than my 19P SS at the same heigth, but I can run the 19 SS higher.<br />Back to your problem...I don't like the looks of your over-all slip #'s, and they appear very close to actual, unless we have a tach reading high by quite a bit..<br />also, there is something wrong with the Turbo...that's not typical results in testing..<br />when compared to a 15X17 alum, that Turbo should have peeled your cheeks back (both sets) and speed should have been quite a jump up if the prop is in factory condition.<br />Even if the tach WAS off, if we use it for just a reference, the numbers aren't adding up.<br />And that 23....6" higher in pitch and only a 200RPM drop, yet 7mph faster????<br />Got me???

 

[Dhadley]

Re: Prop & setup guys

Z II, I understand your confusion. The numbers didnt look right to me either. Going from a 17 alum to a 23 alum and only losing 200 rpm doesnt make sense. Nor does a 7 mph gain with a 200 rpm loss. Even if the 17 was in bad shape that would explain the 7 mph but the r's should be much higher.<br /><br />The only props that reacted even close to theory were the 23 and the 20. Was the 20 a 4 blade? And those percentages dont seem right for a typical Turbo (as Kenny said).<br /><br />17 alum @5800, 42<br />20 ss @6000, 48<br />23 alum @5600, 49

 

[Zaxxon II]

Re: Prop & setup guys

I'm going to retest with just me and no load to see what happens. I'll take all three props and pull out and change each time, something must be off. The ss 20 is off an in/out drive if that sheds any light. As far as I know it hasn't been reworked but doesn't look like it has any cup.It also doesn't have the ring around the exhaust hub like the other two. The 17 was damaged and I had it redone. The 23 is new and I vented it. Anything else I should look at for the slip?

 

[Zaxxon II]

Re: Prop & setup guys

By the way Walleyehed, my 15X17 is the same as yours a 391200. Who makes it?

 

[walleyehed]

Re: Prop & setup guys

391200 is the OMC P/N for the 15X17.<br />Dhadley is going to respond on the issue of the Turbo, I think...<br />I believe the Turbo for I/O's is specifically made for "Under-water" running, and I have no data for "that" prop, but Dhadley will have the info you need.<br />That will make a difference in slip when run on an outboard at the heigths that work better with moderate to heavy cup and Rake.