Have I brought the right prop?

[Kleyny]

My factory prop finally got way too many chunks out of it to work to its full potential.
The old prop was a 10 1/4" dia with a 13" pitch merc prop. The new one is a solas 11.1"dia 14" pitch compression cast alloy.

I took it out and the motor would not rev to the limiter(5500= limiter I got 5200 trimmed to over 3/4 trim). But I am very happy with the hole shot and the cruise speed.
I come home and lifted the motor, took her back out i got to 5400 with the trim up over the half way mark.
Lifted her another hole now she will hit the limiter at around half trim but once I bring it back to 1/4 trim she drop to around the 5200-5300 mark.

At 1/4 trim I can just see the cav plate at cruise and over. The spray I am getting off the motor when at half trim is a fare bit. But the rooster tail I am getting is pretty cool.

All this is done with 3/4 tank of fuel just me and a light esky.

The motor height is now 2" about the lowest part of the hull. (I would have thought too high)

The specs for my motor says it wot rev range is 5000-5500.

50% of my boating is just me 85kg, 30% is me and another 75-90kg, 19% me and 2 others 75 and 90kgs and 1% is it loaded to the hilt with camping gear.

Am I loading the motor up too much with this prop?

Should I go back to a 13" prop?

Thanks

Neil

If anyone is interested the old speed specs are 42ks@4500 59ks@5500.
The new specs are 48ks@4500 and 64ks@5500 with a mean rooster.

[Blackened]

G'day

I think you're pretty much about set. Keep it as you have it now.

Dave

[Seahorse]

What Motor On What Boat?

[gone_fishing]

seems as to be in the working rev range..
but sounds to me possibily a bit to big ...how does it go when loaded up?? ...
near say that you'd nearly be better off with a smaller pitch :)

[Blackened]

G'day

He's achieving WOT with the new prop, with a greater cruise speed and fuel. economy will also increase.

He's also happy with hole shot. Seems spot on. My guess is the engine would be anything from a 25 to 40hp or there abouts.

Dave

[Kleyny]

The hull is a 4.6m quintrex dory. 06
The motor is 60hp merc 2 stroke. 04
I do want to load it up and see how it goes before I make the final decision.

neil

[Kiwijohn]

Why not get Solss to fix up your old prop? It costs a lot less than a new one and looks the same.

That way you will have two props and can swap around depending on load.

[FNQCairns]

The prop doesn't suit, it's a dog like most/all are with a 5200 WOT ceiling.

Can you find/swap to a prop to test with the same diameter as your old one but with the pitch of your new one? as a quick assumption it may just work and if it does there will be advantages.

5500 is pretty much the lowest RPM your engine should see under a full load. just like in a car you have complete control over the RPM it reaches.

[robothefisho]

Sounds setup perfect to me. 5500 is the top rev range for an older 2 stroke mid horsepower. If you can hit the limiter with just you in the boat its perfect, bit of load and it'll bring it down a bit.

[Kleyny]

Righto,

Went for another run today and took the whole family dogs included.
The extra weight was around the 150kg mark.
The hole shot was still ok but harder than by myself and i still hit the limiter @5500. It was a little harder to hit the limiter, I still had to trim the motor out to half way to get the revs up over 5300.

At the limiter and 1/2 trim there is only 1/4ish of the hull in the water.

When I go back to cruise revs and give wot it still gets up to the limiter with a bit of extra effort. I didn't lurch forward as much as it did with just me in it.


any more thoughts?

neil

[Moonlighter]

Neil

See the post I just put up on the thread called "WOT".

Based on what the guys from the PropGods say in that post, I reckon you're spot on with that new prop. But have a read and make up your own mind.

Cheers

ML

[FNQCairns]

Oh! Ok.... i must have missunderstood/read your original post, if you find 5500 RPM at some stage irrespective of trim then on average you are doing ok. you can do better with time and more money but on any one prop it's close enough.....and esp with a full load.

[Kleyny]

Neil

See the post I just put up on the thread called "WOT".

Based on what the guys from the PropGods say in that post, I reckon you're spot on with that new prop. But have a read and make up your own mind.

Cheers

ML


Oh! Ok.... i must have missunderstood/read your original post, if you find 5500 RPM at some stage irrespective of trim then on average you are doing ok. you can do better with time and more money but on any one prop it's close enough.....and esp with a full load.

Thanks guys.

Looks like I keep this prop.

I would love to go to a stainless prop and get it set up perfectly but with the sandbank finding and the rock moving I do I think I'll be throwing money down the drain.

Now can anyone tell me why i have a heap of spray coming off the motor when its trimmed over 1/4 trim? It doesnt really worry too much but I don't see other boats with this amount of spray.
I am happy to have the rooster tail but;D.

neil