Reply With QuoteThat's on the plane mate and at least the dealer is willing to help you out, I wish I could say the same with the guys I bought mine off.
Is this when putting along or when on plane? Where should it sit in calm water...boat just floatingOriginally Posted by marto78
That's on the plane mate and at least the dealer is willing to help you out, I wish I could say the same with the guys I bought mine off.
What model merc prop is it?
I think the gearbox ratio of your merc is 2.33 correct?
So heres the formula for working out max theoretical speed.
Boat speed (km/h) = propeller pitch (inch) X engine speed (r/min) X .001524 X propeller efficiency / gear ratio
For your boat 15x 6000x 0.001524 /2.33 = 58.8kmh at zero slip.
But you running a 4 blade looks like your engine doesnt have the power to spin it to 6k.
so your mate with a 90hp suzuki, if he can spin his prop at 6300 and run a 17p he could theoretically get 63km/h.
Generally a 4 blade wont be as fast as you nearly always need to drop a pitch.
In anycase if you drop to a 13p your max speed will only be a smidge above 50km. but your are no where near max revs, so you need to change somthing but dropping a pitch to achieve this seem like last resort.
Depends on what you want out of your boat.
If i were you, Id rebalance the boat a bit but lift your engine for sure as a test and slap on a neutral lift 3 blade for more speed.
Often lifting the outboard a hole can solve the porpoising. As your engine isnt driving the bow upwards from as deep. so flattens the ride out and should also gain you some speed too.
Then maybe try a different model prop if your boat runs sweet lifted a hole
Thabks so much for the detailed reply
I took it for a run today and am almost positive the engine is too low as I can't see the cavation plate when running
https://imgur.com/gallery/U01UGrh
The blue line sits on top of the water line when planing and I believe the red line is the cavitation plate? If so then cavitation plate is 60mm below the blue line...hope that makes sense
yeah, engine is too low for sure.
From that video the motor looks like it could even go up 2 holes.
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