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Author Topic:   Prop for 93 17'Outrage
Tuna Man posted 05-06-2003 10:58 PM ET (US)   Profile for Tuna Man   Send Email to Tuna Man  
A family member purchased this boat last summer. He is in need for the correct prop. He has a Yamaha 115hp and is turning 5900 when trimmed and has an average load on board. The prop he currently has is a stainless (probably Yamaha) painted black stamped "16K". According to his not so accurate speedo he is moving at 41mph. I let him borrow my "17K" stainless and he got 6000 rpm from the motor at 39mph trimmed, same load. Mine may have a slightly smaller diameter, I did not see them together. Hole shot is excellent, but he is afraid he may blow the engine up, I tend to agree.
What do you guys run? What do you think 19"? I realize GPS is the way to go, but my handheld is on the fritz and he does not own one yet. What speed should he get with the correct prop at top end?


Sal DiMercurio posted 05-06-2003 11:20 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
Scott, first things first.
We need to know what the maximum factory recommended rpms are for that particular engine.
Second, something dosen't add up here as he should have lost 200 rpms, not gained 100.
1 inch of pitch more in the prop [ from 16 to 17 ], will take 200 rpms from the engine.
If the diameter is less an inch, it might not change anything & could add 100 rpms.
I think he ran the boat the second time with your prop, on a colder day & conditions were different.
I'm not all that familiar with Yamaha props, but every other prop , the higher the number the higher the pitch.
I'd try a Merc prop, [ they fit each other ] size 12-1/2" x 17p & see what he gets.
Off the top of my head, i think that engine is rated to 5,500 rpms, if thats the case, he needs to buy a new prop with 2" "MORE" pitch then the prop he got with the boat [ 16k ], that will bring his rpms down to 5,500 rpms.
Tuna Man posted 05-06-2003 11:59 PM ET (US)     Profile for Tuna Man  Send Email to Tuna Man     
I agree with you about going up in pitch should reduce RPM. However my 17" prop may have more cup or rake? Maximum RPMs for that year is 5500, so he is above the redline. Both tests were done this past Sunday, but you are correct Barnegat Bay here in NJ was starting to kick up when he did the test with my 17" prop.


Sal DiMercurio posted 05-07-2003 01:20 AM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
Scott, if your 17 had more cup or rake, it would really pull the rpms down, not up.
If the water was smooth when he ran his prop, the boat couldn't really break loose, & when he put your prop on, if there was a 1'- 18" chop, the boat would run free & far less water resistance, thus being able to turn more rpms, but still dosen't calculate, as more pitch, more cup or rake equals far less rpms.

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