Mercury Spitfire Prop

[banjo]

I was wondering if anyone has had experience with these props. Are they a great improvement over a standard 3 blade.
I have a 15 ft aluminum with a 40 hp...with a standard 16p 3 blade prop. I have a hydrofoil on it (was there when I bought the boat) which gets it on plane good... but cavitates at the slightest turn. Also running through weeds at slow speeds it tends to suck in lots of gunk that gets caught in the engine and outflow... possibly helped by the hydrofoil... I am not sure about that. So, I was going to take off the hydrofoil and was wondering if a spitfire prop would be a good bet.

[NMG]

What type of engine do you have? a 16P seems way too high for a 40HP . . .

Anyway, the Spitfire props get great reviews. They are said to improve hole shot quite a bit over a three blade, provide better handling and less ventilation. There might be a slight loss in top end over the same pitch three blade, but based on the reviews I've read, it's not significant if it happens. Some folks actually get a bit of a bump in top end because the better grip lets them raise their engine a bit.

[Crunchy]

I upgraded to a 19 pitch, 12.5 inch spitfire on my 90hp. Originally I had a 21p prop on it.

Original prop, top end was 41.5mph.

With the spitfire I have gotten 43.5 with full 80L of gas and 2ppl, so I would think I can squeeze 44 easily out of it.

I first noticed how smooth the prop is. You can hear and feel it when cruising, it's obvious.

Hole shot I would say is improved my 50%. it really lifts the stern out of the water.. I can trim up a lot more than before. It also takes a lot more for the prop to blow out on turns.


Not sure how much effect it would have on a 40hp, but it's the best investment I made for my 90

[pasquini]

I upgraded to a 19 pitch, 12.5 inch spitfire on my 90hp. Originally I had a 21p prop on it.

Original prop, top end was 41.5mph.

With the spitfire I have gotten 43.5 with full 80L of gas and 2ppl, so I would think I can squeeze 44 easily out of it.

I first noticed how smooth the prop is. You can hear and feel it when cruising, it's obvious.

Hole shot I would say is improved my 50%. it really lifts the stern out of the water.. I can trim up a lot more than before. It also takes a lot more for the prop to blow out on turns.


Not sure how much effect it would have on a 40hp, but it's the best investment I made for my 90

I put a 13 X 17p Spifire on my Princecraft 182SS w 115hp EFI 4-stroke. Replaced a 13.25 X 17p 3-blade Black Max. I would echo Crunchy's observations. Hole shot is great. No more ventilation in corners. Not a WOT kind of guy but Top Speed is unchanged at 41.5mph on the GPS. WOT is just under the 6400 RPM limit. At crusing speeds (30 mph) the engine is turning about 200 rpm slower than than the 3 blade. Best $200 upgrade yet.

[banjo]

My motor is a 40hp Mercury 3cyl 2 stroke, oil injected from 1999.
The prop that's on it has some numbers stamped on it, and at the end it reads 16p. So I am assuming its a 16 pitch...is there another way to tell? I don't know too much about this. PS... what is the 13 when someone has a 13x16 prop?

[lape0019]

The numbers you have found indicate the diameter of the circle the prop will make in 1 revolution as well as the pitch.

If someone says 13 x 16 it means the diameter of the prop is 13 and the pitch is 16.

There are other ways to tell the pitch, but you probably wont be able to do it without some very specialized tools.

Not that it really matters but if the numbers you are reading are stamped on the fin or the housing on the outside, chances are that it is an aftermarket prop. If they are cast into the hub area and you can only see the numbers when the prop is off of the motor, it is a Mercury prop. This is my experience with aluminum props anyway.

My guess is that you have an aftermarket Michigan Wheel prop on there now.

I am intersted to see how this thread turns out as I am in the middle of trying to figure out which prop to buy for my motor and like the idea of a 4 blade prop. The 17P 3 blade that was on there is pretty beat up and I think the hub is gone and the 19P that came with the boat is too much pitch to hit the maximum RPM at WOT. With the 19P on, I can only hit 5100rpm when max rpm is 6000

Adam

[NMG]

lape0019 had it right banjo, that means your prop is 13 inches in diameter with a 16 pitch. In order to figure out what size you need, to have to know the maximum RPM's for your engine and the RPM's you are currently running. You want to be able to hit the max RPM's or very close to it with your normal load. Do you have a tach? I don't know much about how the 2 strokes run but you might actually be okay because I suspect they have a lower maximum RPM than a 4 stroke (a 40-60 HP 4 stroke would typically run anything from an 11 to a 13 pitch to get up near 6,000 RPM).

For what it's worth, I'm really considering a Spitfire for my Yamaha F70 this year as well. The Quicksilver Nemesis is the same prop and a little bit cheaper from what I can tell. I'd probably run a 13 pitch . . .

[banjo]

Cool. Good info.
The exact number on my existing prop is 48 73142 A40 16P. A quick google search tells me that its a 10x16.
The mercury website prop selector (for boat length) recommends a 10.1 x 14 or 15 P.
I dont have a tack to tell the rpms. I am sure all local shops can order these in... but do any 'loan' out props to test on the water?

[NMG]

Generally speaking, you are going to gain 150-200 RPM for each pitch you go down. So, if you go from a 16 to a 14, your RPM's should go up 300-400 RPM. The problem you might run into without a tach to help you see where you are, is that you run the risk of running your engine above the max RPM's, which could cause damage.

If you are happy with your current performance, except for the cavitation, I'd suggest getting as close to your current pitch as you can or at least talking to a Merc dealer to see what they suggest. I'm not aware of anyone in the Ottawa area that lends props, which is really too bad because I'd be interested in trying some out myself!

[Cyber]

Generally speaking, you are going to gain 150-200 RPM for each pitch you go down. So, if you go from a 16 to a 14, your RPM's should go up 300-400 RPM. The problem you might run into without a tach to help you see where you are, is that you run the risk of running your engine above the max RPM's, which could cause damage.

If you are happy with your current performance, except for the cavitation, I'd suggest getting as close to your current pitch as you can or at least talking to a Merc dealer to see what they suggest. I'm not aware of anyone in the Ottawa area that lends props, which is really too bad because I'd be interested in trying some out myself!

Not sure if he still does or not, but Mike's Marine in Blacks Corners used to "lend" props.

[banjo]

Cool. Good to know. Unfortunately, I don't have that boat anymore... Although I do still have the lower unit and prop. I will probably list it for sale, I wonder if repair shops buy used parts...

[Champion1]

I'm not aware of anyone in the Ottawa area that lends props, which is really too bad because I'd be interested in trying some out myself!????

[bramsey]

A Mercury Spitfire will make a difference on all the above questions except weed issue. If you want to help the weed issue there are little cutters you can glue on the side of the gearcase to cut the weeds as the prop grabs them. Your RPM on that motor is between 5500-5800rpm with 2 guys guys half tank of fuel and average load. Understanding you don't have a tach that is a hard one to judge where your RPMs are at but I would say a 15 pitch is going to be what you would want on your boat (to be on RPM safe side.) Depending on your current wiring harness in your boat your may believe to purchase a tach and connect three wires and now you have a functioning tach. But I would highly recommend a spitfire!