aluminum prop comparison

Stinnett21 said:

The Spitfire is Mercury's attempt at building a Rev 4 out of aluminum. So it doesn't surprise me the thicker aluminum 23 matches the 21 steel.

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The blade shape , size , and rake are very different from a Revolution 4 so doubt it’s an attempt to copy. It just didn’t perform any different than a michigan vortex, which makes the published info on it look like BS

Price first. Quality last. New wave logic.

All this talk got me to thinking and I made a few runs the other day in current setup. Seems pretty typical to what I remember except top end speed is down and slip is up accordingly. Boat will stay on plane right at 2500 and between there and 4000 slip numbers seem ok above or below that and it goes up pretty fast. When the prop was new I feel like the speed was better at 4500 up something like 48 wide open but I don’t have any of that written down. Between about 2700 and 4000 it feels pretty good which is the lowest slip numbers right now.

22 2500
29 3000
33 3500
38 4000
40 4500
43 4800 (still has throttle left)

Overall still under propped which I already knew and I assume numbers would all improve going up slightly in pitch. Also wondering if this prop has changed over the past 6 year's and doesn’t hold water as well as I remember

As previously said you need to go WOT to get an accurate baseline. Just do it momentarily enough to get a reading and back down. You won't blow your motor up if it's just for a moment.

Stinnett21 said:

As previously said you need to go WOT to get an accurate baseline. Just do it momentarily enough to get a reading and back down. You won't blow your motor up if it's just for a moment.

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Not worried about it blowing up but it runs into the rev limiter. Can't get a true WOT read.

MBAKER said:

Not worried about it blowing up but it runs into the rev limiter. Can't get a true WOT read.

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if you have more slip quite possible you have some wear on the prop maybe some burn marks on it doesnt cost much to run a AL prop through a rebuilder. if one is not local try Prop MD in minnesota, I have done mine via mail order. Send it in after end of season

Responding to your original post. You could get the same blade/diameter/pitch prop from different manufacturers and get different results. The reverse is true also. I have 3 different props from 2 manufacturers that all gave the same #'s.
propping can get expensive.
From all you've said, increase the pitch by 1" and keep everything else the same, including the manufacturer.

MBAKER said:

Not worried about it blowing up but it runs into the rev limiter. Can't get a true WOT read.

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The rev limiter is your WOT. Report your readings at the rev limiter.

Stinnett21 said:

The rev limiter is your WOT. Report your readings at the rev limiter.

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I think he still has throttle to go when he hits the limiter

limiter is normally 5100 or so maybe a touch higher for MPI

Correct I still have throttle left, at 48-4900, that’s just below where rev limiter kicks in. By feel and how much throttle is left it ‘feels’ like it might run 52-5300.. It’s not MPI, it’s a 5.7 carbureted.

I’m planning on trying a couple different props next chance I get. After talking with a couple others I’m Now just wondering if the prop could have fatigued and changed shape a little bit to where I’m not getting same top end and/or it’s slipping more on top than it used to. Not super worried since it still works well below 3500, just wasn’t expecting to over rev that much compared to what I remember. One of those props is the old 3 blade 19pitch that I have recorded numbers for so it should be a better comparison.

MBAKER said:

Correct I still have throttle left, at 48-4900, that’s just below where rev limiter kicks in. By feel and how much throttle is left it ‘feels’ like it might run 52-5300.. It’s not MPI, it’s a 5.7 carbureted.

I’m planning on trying a couple different props next chance I get. After talking with a couple others I’m Now just wondering if the prop could have fatigued and changed shape a little bit to where I’m not getting same top end and/or it’s slipping more on top than it used to. Not super worried since it still works well below 3500, just wasn’t expecting to over rev that much compared to what I remember. One of those props is the old 3 blade 19pitch that I have recorded numbers for so it should be a better comparison.

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Based on that feel I would go up 2" in pitch would probably get you there but you might loose holeshot and pulling ability some.

you could also have cup added to your current prop

Swapped on a MW 14.5 x 18 4 blade I had in the garage. New numbers below, felt like it had more grip below 3000 which is evidenced in the numbers. MW had about 14% slip to 4000 then went up where the PT was 18-20 then dropped to 15 at 3000-3500 then back above 20. At 2500 the MW was 2-3 mph faster and would stay in plane down to 2200. Slip numbers under 3000 dropped considerably and you could feel it pull down a little bit more out of the hole just about 2500-2700 Where the powertech probably slipped a little bit and powered right through to 3000 when everything equaled out and slip dropped. Overall between 3-4000 they act pretty similar above and below that the MW seemed to be more efficient but the PT almost feels like it pulls better. Having been a few weeks between it also feels like the boat stayed flatter with the PT like it had more stern lift and the MW had more bow lift.

Michigan
2500 26
3000 30
3500 35
4000 38
4500 41
4900 44 (Rev limiter)