Rank: Member
Groups: Member
Joined: 5/20/2008
Posts: 10
Points: 30
Location: Key Largo, FL
|
Ken,
Looking to help a buddy get into the right prop. He is running a 17P Mirage Plus and is getting 5100 RPM and 40 MPH, he complains about how long it takes to get on plane. I switched him to 15.25 X 15P Yamaha SS prop that I use as a spare on my boat. He now is getting a much better hole shot and is turning 5800 RPM and getting 38 MPH. I explained to him that the yamaha 150 four stroke can spin up to 5900 rpm. From what he tells me it appears that the 15p is a much better fit for him but he thinks his engine revs to high and it is bad for the engine he is trying to compare where the speed was on both props at 5100 rpms and stating he lost 7 mph. Can you please chime in with your expertise and help us solve this friendly debate.
Thanks...
|
Rank: Administration
Groups: Member
Joined: 2/27/2007
Posts: 1,789
Points: 5,080
Location: Sarasota
|
Just look at the fuel flow guage, that is the true test of how hard the engine is working.
Its easier on the engine to turn higher rpm. The engines are made for it. rpm range for that motor is 5000-6000, The Mirage is really holding that motor back.
Don't compare rpm to rpm, compare speed to speed. If he cruises at 30 mph, or so, compare fuel burn at that speed.
Although he turns more rpm to go the same speed, fuel burn will probably be the same or a little better then it was with the Mirage.
5800 rpm is perfect. I normally shoot for 6000.
There are better props out there, An Enertia 15 pitch would likely outrun the Mirage on top speed, and still get good holeshot, and it will turn 5800-6000 rpm.
But between that Mirage and the Yamaha 15 pitch, I'd stick with that 15 pitch.
|
Rank: Member
Groups: Member
Joined: 5/20/2008
Posts: 10
Points: 30
Location: Key Largo, FL
|
Thanks Ken as always very informative...I think I got what I was looking for.
|
