Sun runner 225, ~ dry2000kg, 5.0 V8 Alpha 1 and 14.5x17. RPM prob

[Panu]

Hello.

My boat is taking only 3400rpm at high speed with trim and speed is 31 knots. even with 1 person or 4.
Is my boat too heavy with this prop and is there a danger to broke anything.


Prop is at perfect condition. fixed week ago. (steel)

Thx.
Captain Panu from Finland

 

[steelespike]

Re: Sun runner 225, ~ dry2000kg, 5.0 V8 Alpha 1 and 14.5x17. RPM prob

Is your boat an 87?
Is your speed by gps?
Your wide open throttle should be about 4400 to 4600 rpm.
A 17" prop seems reasonable.
To make up about 1000 rpm would need about a 12" prop pitch.Not reasonable.
Is the bottom clean and smooth?
Is the motor in excellent tune?Good compression?
Is the throttle opening all the way?
Is the timing set right and advancing as it should?

 

[Panu]

Re: Sun runner 225, ~ dry2000kg, 5.0 V8 Alpha 1 and 14.5x17. RPM prob

Thx to reply.
Yes its 1987 and speed taken with my android navionics plotter.
2 days ago i got 3800rpm and 32,5knots with luck "i quess" 3 persons onboard.
Prop is in perfect condition (fixed few week ago and bottom of the boat is also at excellent condion.
Ill have to check the ignition.. How much it can effect? Seems its not in correct position cause at the engine start i get feedback(kick) from engine when starting. if u understand.

At the cruising speed i run ~2900rpm and 22-24 knots.