S/s Prop Upgrade??

[Adam F]

I think I'll probably answer my own question here, but anyway...

 

I have a 13.25" x 17 Alloy prop on the Honda at present. I want to upgrade to a S/S and Warrior tell me that the Alloy prop revs to about 5600/5800. The engine is rated to 6000 WOT.

 

Warrior recommend an upgrade to the 16" pitch S/S prop, but these are like like rocking horse poo and only available from Honda at over

[Coddy]

Why not go for the Hustler type with the replaceable centre.

 

You know you will ding that prop in Christchurch so having an instant replaceable prop is the cheapest and easiest way to go.

 

Have a look here Adam Outboard Props

 

Coddy

Edited February 14, 2007 by Coddy

[Paul J]

Adam,

 

Talk to the guys at Prop Revs

 

PJ

[Adam F]

Ive talked to prop revs, they dont carry a 16, only 15's - hence my question and yes coddy the one they offer has a universal hub.

 

The reason for wanting a S/S is to have a more durabel prop for Xchurch, plus Ill have the alloy spare for when it's really shallow.

 

Back to the question - am I going to get too many revs with a 15" pitch?

[Seamouse]

I'd say the answer is probably yes, you'll over-rev. Within 200rpm of the quoted WOT figure on a loaded boat would be near enough spot on. They say each inch of pitch adds a hundred rpm or so (?) but going from a 17 pitch to a 15 pitch on a 75hp put my WOT revs up from 4200 to 5200 That'd presumably be because the smaller pitch allowed me to reach the power band, which then gave me more rpm and MORE power. Not an issue on your boat where you are already getting near on full rpm.

Other points - prop design really matters. The old style evinrude 17 pitch gives 4800rpm, the new monstrosity just 4200rpm. Plus I think maybe stainless props run more efficiently. although I can't quite see the logic in that myself.

 

Nice to have a new toy to play with though. Any idea what she'll do on a flat day? 32kts?

 

Steve

[Adam F]

Owners I have spoken to tell me that it's a rare day when you can open the throttle - however I have been told that 38-40 knots is attainable when lightly loaded - I'm expetcting about 32-32 will all th kit onboard.

 

Re. the prop, I think the best idea is to wait until the Alloy prop comes back and run the boat up on that to see what it pulls. Its just a shame that the only 16" prop is from Honda at silly money.

[duncan]

I know it sounds obvious but - surely they will let you try a 15 on the basis that you will buy it if the revs work out OK and buy a 16 if they don't?

 

rot is 1" - 200 rpm all other things being equal

 

personally I switched from alloy to stainless after the 2nd incident - in my case this was a nylon bale strap that destroyed all 3 blades completely! I never had a problem after that with SS for the next 2 boats and 500hrs run - sand and shingle simply polish them!

 

again there have been many shools of thought re comparable pitches etc - most driven by differences in the design of the props I believe. I swapped out like for like in the Quicksilver range and they seemed similar in revs but with the SS delivering a smoother running feel and about 5% more speed at the same revs.

 

Back to your case - the 15 will deliver a hell of a hole shot, you tend to travel fairly loaded so on balance I would believe you aren't going to change the gearing to the detriment of either economy or engine loading and that the 15 will be fine.

 

I still think they will let you try out (but maybe not if you use it from Christchurch!) Right now Poole Harbour is a great opportunity to test this sort of thing.

[great white]

Adam you seem to have received all of the info already

 

We run our 7 RIBs with hustler props so that we can easily change the defective parts

 

As a new outer part costs the same as having 1 blade repaired and the inner about the same as rebushing the costs are equivalant without the wait for a repair

 

If I had seen this earlier I am sure we have some in stock that would have got you out at the weekend, I think that they are 17" pitch

 

We get them from Prop Rev so I would be surprised if they do not stock the correct one

 

Charlie

[toerag]

SS props work better as the blades can be made thinner. However, hit something hard and the chances of you breaking your drive are way higher than with alloy or grp.

[Coddy]

If you now have a 130hp won't you be able to turn a larger prop now?

 

Coddy

[duncan]

SS props work better as the blades can be made thinner. However, hit something hard and the chances of you breaking your drive are way higher than with alloy or grp.

that would be why they have rubber bushes?

[toerag]

SS props work better as the blades can be made thinner. However, hit something hard and the chances of you breaking your drive are way higher than with alloy or grp.

that would be why they have rubber bushes?

Dunno. I enquired about them as the rear props on duoprops are susceptible to 'cavitation corrosion' and I thought SS would remove the need to repaint them every couple of years and my volvo dealer advised against it.

[duncan]

SS props work better as the blades can be made thinner. However, hit something hard and the chances of you breaking your drive are way higher than with alloy or grp.

that would be why they have rubber bushes?

Dunno. I enquired about them as the rear props on duoprops are susceptible to 'cavitation corrosion' and I thought SS would remove the need to repaint them every couple of years and my volvo dealer advised against it.

most stainless OB props have a rubber bush designed to 'fail' as part of the drive train in the event of a 'sudden deacceleration' ; this also applies to the Alpha drives (which I believe share a fair amount with the larger Merc OBs including props).

 

duo prop arrangements share nothing with the OBs and I am not aware of any 'hub' arrangements - however I thought this thread was about Adam's OB requirements

 

absolutely agree that the main advantage is thinner blades without flex associated with the alloy or composite material.

 

personally I also like to be comfortable that I am polishing the prop rather than destroying it where silt, sand or light gravel bars have to be traversed.......

 

re the 'stainless bust drives' argument - yes but....in practice you have to be extrememly unlucky (and quiet inventive) to bring the prop to bear on a solid object without contacting the leg itself..........

 

main reason they aren't standard on all drives is price, price and price - they would add about 20% to the base volvo drive I believe; not great from a marketing perspective for units designed to be cost effective drop in's to base boat models.