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Old 30 March 2016, 05:16   #1
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Buying new prop - mercury spitfire 4 blade, what pitch for 4m rib mono - 1987 60hp?

Anyone here with experience? This is for fishing and skiing - max 3 adults most of the time, probably 2 or just me..

I probably cant take it back so hopefully will buy right first time -

2 very well known boat mechs/builders said 13" - It has a 14 3 blade on it there now but I spun the hub on my first "voyage" of about 30 yards...

Ive pinned it and will keep it as a backup prop onboard..


attached is a pic of the pinned prop hub - perhaps it would help someone in the future to at least use the old one for a backup / emergency

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Old 30 March 2016, 09:35   #2
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I had a 10.5 x 15 pitch spitfire prop on a avon 4 metre with a merc 50 two stroke. Pulles really well up to 37 knots with loads of grip. Great prop
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Old 30 March 2016, 09:47   #3
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really.. just ordered the 13 lol.. i did a prop slip calculation and the 13 does seem to provide better numbers compared to the 15.. but tx fr the real world feedback.. apparently the mercs are geared a bit higher, so a lower pitch prop might offset that for a nice balance.. having said that the merc prop calculator jumped around between 13,14 and 15 pitch depending on what I entered.. the more weight the lower the pitch.. I guess in rough weather with 3 adults against wind the power might be more beneficial than whizzing along at higher speeds.. the added acceleration for wakeboarding / skiing with a load shd also be nice with the 13..

how i wish i could test the 15 and 13 real time!

How was yr holeshot and what was the loaded weight? shd be close to mine i think..

Heres an interesting read, esp the first reply!

http://forums.floridasportsman.com/s...Any-experience
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Old 30 March 2016, 10:29   #4
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Tbh it was light but brilliant holeshot. A loaded boat would benefit from 13 pitch
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Old 02 April 2016, 23:22   #5
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ok so after some more research it seems a 10-20% prop slip is ideal.. the 13 was giving me almost 0 - the rep here also recommended i try the 15 instead, either way.. i will see - on 14" 3 blader today got up to 33kts alone in calm water - jumped on plane in under 2s, so i guess thats ok - didnt have to touch the motor after setting it up on land, idled perfect - teeny bit of hesitation on accel but its less than 1/2 a second - then kicks in, might play with mix screws on water later..

Any tips for tuning these for max power? ie throttle / timing ?
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Old 03 April 2016, 01:48   #6
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Quote:
Originally Posted by Fstarocka View Post

Any tips for tuning these for max power? ie throttle / timing ?
Yep, set it to Mercs recommended settings and leave it alone or you'll end up with a nasty melted mess.

In real world use, the odd 1/2hp you might gain won't even be noticeable. Your prop experiments will be far more beneficial.

If you're going for a 15, don't bother with a 4 blade. There's not really a lot of point in going for more than a 3 blader on a 4m rib unless you've got a big load to carry on a regular basis anyway, but a 15" 4 blader will quite possibly end up leaving the motor labouring at WOT.
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Old 03 April 2016, 03:27   #7
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I was hoping to get it set up correctly, the manual isn't all that clear about the primary setup.. I have a 13 inch on the way.. The spitfire props do get good reviews..

The boat pops onto plane instantly cos its light, and if I can achieve better economy at lower cruise rpms that wd be great.

I spun my hub last week that's why looking at new prop.. The spitfire seems a great option..

I'm going to run the 13 and 15 .. Sales guy here seems to have a clue about gear case, slip etc and reckons the 15.. If these props do have great holeshot I might get away with the 15 all round..

Most of the time I'll be whizzing about fishing with 2 adults fishing.. The boat is real light too..

All in all I'll be doing real time testing..

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Old 03 April 2016, 04:41   #8
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Nosssss.. your back.. yeehaaaaa!!
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