Hi five prop

teamplonker · 15 May 2013, 21:52

Does anyone know if a hi five Merc prop will fit my Honda 75.

Nos4r2 · 15 May 2013, 23:07

What do you want to do-use the SR as a tugboat?

It'll slow it up IF it fits.

Assuming you can get one for the same size gearcase and get the right hub adapter there's no reason it won't fit.

teamplonker · 15 May 2013, 23:14

I have raised the outboard again as the revs are still to low.
I was advised to get a 19p stainless prop and i have just seen a secondhand hi five on ebay and thought it would give more acceleration than a standard 3 blade ?

Nos4r2 · 15 May 2013, 23:24

It will, but it'll reduce your top speed.

A 19p 5 blade will do less rpm than a 19p 3 blade. You're better off doing the comparison on like for like props and only changing one variable at a time.

mick · 15 May 2013, 23:31

My 90 s are on 17" and rev up to 6 k no problem I have borrowed a 19" that I am going to try on one side to see what a difference it makes to the reves

Pikey Dave · 16 May 2013, 07:34

Quote:

Originally Posted by mick

My 90 s are on 17" and rev up to 6 k no problem I have borrowed a 19" that I am going to try on one side to see what a difference it makes to the reves

That'll be you going around in circles then

martini · 16 May 2013, 10:09

Quote:

Originally Posted by mick

My 90 s are on 17" and rev up to 6 k no problem I have borrowed a 19" that I am going to try on one side to see what a difference it makes to the reves

You won't get any useful data from changing one prop, the way twins affect each other.

Sent from my portable speaking device using Rib.net

mick · 16 May 2013, 10:32

Quote:

Originally Posted by martini

You won't get any useful data from changing one prop, the way twins affect each other.

Sent from my portable speaking device using Rib.net

So how do I do it one leg in and one out or just leave it alone

Nos4r2 · 16 May 2013, 10:38

Change them both or leave it alone.

mick · 16 May 2013, 10:45

Quote:

Originally Posted by Nos4r2

Change them both or leave it alone.

I only have one its the one Chris Caton had spare

Nos4r2 · 16 May 2013, 10:52

Quote:

Originally Posted by mick

I only have one its the one Chris Caton had spare

You'll have to get another then.

Lemme put it this way, it's the equivalent to putting a 19" wheels on one side of the car and 17" wheels on the other.

mick · 16 May 2013, 10:55

Fair does will wait for another to come along

teamplonker · 16 May 2013, 14:22

Quote:

Originally Posted by Nos4r2

It will, but it'll reduce your top speed.

A 19p 5 blade will do less rpm than a 19p 3 blade. You're better off doing the comparison on like for like props and only changing one variable at a time.

Thanks for all the advise but I have given up

, I took the boat out for a test today with the outboard raised so the cav plate is 1" above the bottom of the boat and a smaller prop ( 15p ) but the revs are still only reaching 4400 when they should be getting 5600.
I have now just taken the boat to Advance Marine to see if the rev counter is telling lies or if anything else is wrong

Nos4r2 · 16 May 2013, 17:50

FWIW, I think a stainless 19p 3 blade on a 75 is probably overpropped by about 4 inches.

However, what you just said sounds like something's not right apart from the prop.

yorfuoj · 19 May 2013, 11:17

To Teamplonker

You don't say what pitch your present 3 blade prop is ! Nor your present "low" RPM ! Is it really 4400 with a 15" prop, extremely low indeed.

You said nothing about speed, did you measure it with a GPS.
Knowing it, and the gear ratio, and the prop pitch, you could approximate the RPM and know if your tachometer is lying.

I would suspect that your engine doesn't deliver the 75hp it should, or that your hull is very dirty, or ...