New boat owner Prop question.

[Trihull&error]

I got a hell of a deal on a 1972 Forester for a 1st boat. and want to know if it is set up properly, I put a couple small dings in the prop nothing that needs replacement but a back up or better prop would not hurt.

Boat is a 72 forester tri hill fiberglass 750lbs dry
Engine is a 1979 85HP Johnson V4 79txl85
running a stainless steal 13 1/4 17 pitch
plate is set even with the keel
Iboats specs this boat as follows
This outboard runabout is 15.08 feet long and weighs 750 (pounds dry). This weight does not account for passengers, fuel, or gear. The beam of this craft is 72 inches

acceleration is quick tops out at 35mph on the GPS I figure this is about a 20% slip is this normal or am I running the wrong prop?

The boat does not have a tach.

 

[dazk14]

Re: New boat owner Prop question.

Are you trimmed up for your top speed run. Does it even have trim.
Does the boat have bottom paint?
Which model stainless prop do you have?
A 17" pitch SS is a reasonable ballpark for that boat, although a 15 footer would often see a slightly higher pitch if watersports were not in the plans.
Can you borrow a tach?

 

[etracer68]

Re: New boat owner Prop question.

Without rpm @ WOT its a crap shooot. I would think the 17 pitch is about right for what you have, but need the RPM too. How are you figuring 20% slip without RPM reading.

 

[Trihull&error]

Re: New boat owner Prop question.

Are you trimmed up for your top speed run. Does it even have trim.
Does the boat have bottom paint?
Which model stainless prop do you have?
A 17" pitch SS is a reasonable ballpark for that boat, although a 15 footer would often see a slightly higher pitch if watersports were not in the plans.
Can you borrow a tach?

Ran it with and without trim, same result, no bottom paint, it's dead stock still the original OMC Johnson prop on it hell it still has all the wiring stickers and spark plug stickers on it under the bonnet, very clean. 2.00 - 1 gear ratio.

Not sure who I can borrow a tach from, will be looking into either who would have one to borrow or finding a deal on one to purchase. Watersports are not in the plans for the near future, maybe when the kids get older. but for now fishing, and occasion lake runs is all she is being used for.

 

[Trihull&error]

Re: New boat owner Prop question.

Without rpm @ WOT its a crap shooot. I would think the 17 pitch is about right for what you have, but need the RPM too. How are you figuring 20% slip without RPM reading.

Playing it by ear I guess, the motor is pretty wound up, I think we are getting into the upper range of that 4500 - 5500 I really should have got a tach before asking, So I will ask this anyone know a place to get a Tach Cheap?

 

[dazk14]

Re: New boat owner Prop question.

Not sure your definition of cheap.

This unit works well. Popular with the jetski contingent. Amazon $27.77 Prime eligible. Hardline is a good company and we've used many of their products over the years.

Hardline Products HR-8061-2 Hour/Tachometer with adjustable input, Resettable MAX RPM and Log Book

Amazon.com: Hardline Products HR-8061-2 Hour/Tachometer with adjustable input, Resettable MAX RPM and Log Book: Automotive

As well as indicating RPM's and engine hours, this unit will record and store maximum rpm attained(resettable).

Installation is a breeze. You simply wrap the single thin lead a few times around the spark plug wire. No power wires are used. Easily removed as well.

It can be used on a wide array of applications(2 and 4 stroke).

Hope that helps.