General Category > General Discussion
New tach, new prop!!!
MarkS:
A 21P may be too much, but I LIKE IT!
http://www.youtube.com/watch?v=5nKLPX-_xVA
Hyperacme:
I'm I seeing 46 mph at 4300 rpm's ?
Speedo is hard to see.
MarkS:
It looked like 39mph, but you're right Gregg, it was hard to see. Haulin' the mail, that's all I can tell for sure! I don't care about turning MAX rpm, (5500) unless it's bad turning less for the old Johnson, what do you think? I was told the "sweet spot" was about 3500, and the 21P is sweet right about there.
Hyperacme:
OK ..
When I'd freeze the video, speedo was very hard to read.
My understanding about props/rpm's/mph is to run a prop that gets your rpm's at WOT some where in the middle of your max. rpm range.
I have heard that proping your motor for under max rpm's is not good for it. ( but that was off a Merc forum )
"Sweet spot" would be your motor would be running 5250 rpm's at WOT and when you throttled down to 3500 rpm's it would run at it's best mpg range of powerband.
If that all makes sence ?
Rich_V174SS:
Marks speedo may be reading in knots and if that's the case 39 knots is about 44.8 mph.
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