Different prop?

[Flynny]

I bought a used '95 70HP Johnson and an '89 Sea Ray 160 about 6 years ago, and had a mechanic set the engine up with the boat. I finally got around to hooking up the tachometer today and took it out for a spin. At WOT, I only reached 5000 RPM. I understand that optimally it should be running at around 5500RPM at WOT. Is it worth buying a new prop to correct this?

The boat is a little less than 17 feet long, and had about 450 pounds of passengers and equipment on board. The current prop is aluminum with a 14in diameter. How do I find the pitch of it (if you need that)?

How much would a stainless prop improve the hole shot? It's pretty good now, but I'm always up for more performance.

 

[steelespike]

Re: Different prop?

Please read the stickys at the top of the page and get us as much info as possible.
Prop size should be near the base of the blades or under the prop nut.
Rpm and speed are critical.

 

[Flynny]

Re: Different prop?

Sorry I thought I gave enough.

28 MPH on plane at 5000RPM.

Inside the prop it says 14 x 17. I guess 17 is the pitch?

Here are some pictures:

 

[steelespike]

Re: Different prop?

Check the height of the motor.The antivent plate just above the prop sahould be about even with the bottom. when the plate is paralell with the bottom. Should be raised to a point just before venting becomes a problem.Could gain a couple of hundred rpm and a mile or 2 per hour for nothing if you can raise it a couple of inches.wouldn't hurt to clean up the blades a little.
As it stands a 19" prop would put you at 5300 to 5500 rpm a little more speed and a little less hole shot.Try to stick with same brand and model for a little more predictable results.

 

[Flynny]

Re: Different prop?

The anti-vent plate is just about even with the bottom of the boat, maybe an inch above above it. I have played with raising the engine on plane, but it ventilates pretty quick.

Something I never understood, how can I could put a bigger diameter prop on the engine if the current prop barely clears the anti-vent plate? Or by 19" do you mean the pitch?

What would be the best way to clean up the prop? The faces are pretty clean, it's just the edges that are beat up from the previous owner driving it into sand. Should I file them out to try to round them or what?