1969 Merc 1000 Prop Question

[hwsiii]

Re: 1969 Merc 1000 Prop Question

Yes, a 13" pitch in the hustler as well, and it is very hard to tell about the speed, because if you are able to decrease prop slip you could gain a little bit of speed. But normally you can expect to lose a little bit.


H

 

[NJCinMN]

Re: 1969 Merc 1000 Prop Question

H,
From what I've read and seen here on the forums my motor should have a 2:1 ratio. There is another mercury lower unit that has a 1.78:1 ratio should mine have been swapped. Does this change much for your calcs?

 

[NJCinMN]

Re: 1969 Merc 1000 Prop Question

I'm gonna trust your knowledge and believe it's 1.7:1. I'll verify it tonight by spinning the flywheel and see how the prop moves in relation.

 

[hwsiii]

Re: 1969 Merc 1000 Prop Question

Nick, we need to know for sure whether your lower unit is a 2:1 or a 1.78:1 as this does affect the final outcome, don't rely on me I just use a database to get the information it can be wrong. So please check it and see.
Make your marks and turn it once the first time, the do it a second time and turn it over twice to make sure, sine the gear ratios are close.
I will be here when you get the gear ratio.



H

 

[NJCinMN]

Re: 1969 Merc 1000 Prop Question

Ok... used my timing marks to track the flywheel and marked the prop. Two revolutions on the flywheel translated to exactly one revolution of the prop. So by my calculations I've got a 2:1 gear ratio.

 

[hwsiii]

Re: 1969 Merc 1000 Prop Question

OK, you need to go to a 13" pitch to get close to your 5,800 RPM you want. In a 4 blade you will have tremendous hole shot and aceleration at all speeds, with the 3 blade do not expect as much.


H

 

[NJCinMN]

Re: 1969 Merc 1000 Prop Question

Well isn't that interesting! Went to the prop shop to get a new one, happens to be a place that specializes in old outboards. They said there's no way with my boat and motor combo I should need any less of a prop and basically guaranteed something is not right with the motor. So back to combing over the motor and might have made a discovery...thinking #6 (bottom cylinder) is either having the plug wire arc to the motor or taking in a very small amount of water into the cylinder. Hopefully the first scenario.

H, sorry for using up your time when it might turn out I never had a prop issue but a motor issue all along, just ran so well other than the low rpms. A million thanks. I'll post when I get this all figured out.

Nick

 

[hwsiii]

Re: 1969 Merc 1000 Prop Question

Nick, it happens some of the time and I hope it just a wire arcing that is the problem.


H

 

[NJCinMN]

Re: 1969 Merc 1000 Prop Question

H,
I'm back. So much for the so-called experts saying there's something wrong with the motor. The only experts I've found are here on iboats. Anyway I went over this motor with a fine tooth comb, even replaced the bottom wire after compression test was good. Found that water jacket was leaking a tiny bit around #6 plug which I've read isn't a big deal but there is a possibility water could be sucked around plug as threads don't seal 100%. Fixed the water leak as well and no change in performance. I'm giving this motor a clean bill of health. So after a little break I'm back to being over-propped. Also RPMS on this inline not to exceed 5400-5500. Earlier I said maybe rev to 5500-5800.

One thought I did have is that I don't get much bow lift on plane. I run pretty level in the water, may be hull design? So looks like I can only go down to a 15P unless I want to spend a fortune on a 14P. Thoughts?

 

[hwsiii]

Re: 1969 Merc 1000 Prop Question

Nick this is the prop you need, it is a Solas Amita 4 blade prop in 13" pitch.It will bring your RPM righ to the top of your recommended WOT RPM.

Price: $108.99 You Save: $27.01 Compare: $136.00 Discount: 19.9% Off
Iboat
Propeller Specifications:

SKU:#1413-133-13
Manufacturer: Solas
Brand: Amita
Material: Aluminum
Diameter: 13 - 1/4?
Pitch: 13?
Blades: 4
Rotation: Standard (Clockwise)

Usually Ships Within: 1 Business


H

 

[NJCinMN]

Re: 1969 Merc 1000 Prop Question

H,
Sounds good. I'll order it from iboats in the next day or two and post performance results.

 

[NJCinMN]

Re: 1969 Merc 1000 Prop Question

Well this post has been a long time coming.
H's prop calculator was almost dead on. I've got WOT @ 6000 rpm and speed of 32. Of course I've only ran it up to those rpms to test. A little high but the low end is worth it. Think I'll keep this setup and just watch the rpms.