Aluminum to Stainless. Which Prop? I have all stats listed Avon Rib 50 hp.......

[boatster]

Hi everyone.<br /><br />I want to run my boat faster or more efficiently. I have a 13' Avon Searider Ex Coastguard rib. It has a 50 hp 2 stroke Tohatsu with a 13.5 pitch 10 1/2" diameter prop. The motor is rated at 5800 rpms WOT. I am currently doing exactly that 5800 WOT. The boat is running around 35 mph on the gps.<br />I have considered raising the motor 1 hole as I can trim the motor pretty far up and still maintain all the above. I also have the Nauticus tabs helping me out. <br /><br />Given all the info above could someone advise on what Stainless prop I should get? Michigan Wheel SS? Tohatsu SS ? Should I go up or down in pitch?<br />Speed isn't as big as my desire to increase fuel economy. I'm going to raise the motor and see how that works but what would be a good SS prop? I want to retire the aluminum prop as a backup even though right now it seems to be doing a swell job.<br /><br />Please any advice info would be greatly appreciated. Thanks.<br /><br />Boatster

 

[Triton II]

Re: Aluminum to Stainless. Which Prop? I have all stats listed Avon Rib 50 hp...

Re: Aluminum to Stainless. Which Prop? I have all stats listed Avon Rib 50 hp...

Generally SS props are a little more efficient than alloy ones due to the stronger material which flexs less and the blades can be made thinner to increase their bite in the water. So going down an inch or so in pitch is often recommended. As an examople I have three props for my Yamaha FT60B - a 13.5 x 15 alloy, a 13.75 x 14 SS and a 13.75 x 13 alloy. The 15 and 14 give much the same revs and speed - about 5600 and 29 kts, the 13 gives 6100 and 27 kts and is much better out of the hole, it's used for tubing and waterskiing. Hope this helps.

 

[walleyehed]

Re: Aluminum to Stainless. Which Prop? I have all stats listed Avon Rib 50 hp...

Re: Aluminum to Stainless. Which Prop? I have all stats listed Avon Rib 50 hp...

I would stay with the same pitch in SS and raise the engine to get the RPM back to 5800...the speed will be higher at the same RPM.

 

[boatster]

Re: Aluminum to Stainless. Which Prop? I have all stats listed Avon Rib 50 hp...

Re: Aluminum to Stainless. Which Prop? I have all stats listed Avon Rib 50 hp...

Thanks for the info guys. <br /><br />Walleyehed, I got the idea to raise the motor from you, reading all your other posts. How much higher do you think I could go? 1"? 2"? I trimmed the motor out almost 80% up on the tilt gauge and I didn't once hear the motor ventilate. My ventilation plate is just about right at the bottom of the boat. THe only reason I ask is because I need to drill an extra hole in the aluminum motor mount to raise it ( I'm at the bottom hole already ). Like I've said I really haven't been able to cause it to ventilate as I tilt the motor up within the tilt gauge range. Thanks again. <br /><br />Also which brand SS prop should I get? I can't find any 13.5 pitch propellers. On one of the blades my prop says 13.5. I need to measure the diameter again to be 100% sure what it is.<br /><br />How about the Michigan Wheels on sale at Iboats?<br /> http://www.iboats.com/mall/propfind...ard&horsepower=50&year=2000&url_mode=standard

 

[walleyehed]

Re: Aluminum to Stainless. Which Prop? I have all stats listed Avon Rib 50 hp...

Re: Aluminum to Stainless. Which Prop? I have all stats listed Avon Rib 50 hp...

I'd go with the 14 pitch if raising the engine.<br />As for "how high" to go...well, that's one of those items that requires some testing. Standard bolt pattern holes are 3/4" from center to center on the top and you will likely be about 1-1/2" above the transom, or 1-1/2" above where you are now, at best with the Rapture.<br />Mark locations at 3/4" so if the 1-1/2" is to much, you can drop 3/4" to take care of it.

 

[boatster]

Re: Aluminum to Stainless. Which Prop? I have all stats listed Avon Rib 50 hp...

Re: Aluminum to Stainless. Which Prop? I have all stats listed Avon Rib 50 hp...

So do you think the 14 pitch Michigan Wheel SS prop is ok? I feel a little cautious when I see it for $100 for a SS prop. Why so cheap? Otherwise I was thinking of going with an OEM Tohatsu SS prop for $225. How different can these props be from each other?<br /><br />I agree I think I'll raise it 1 1/2" and if it doesn't do so well I'll drop 3/4". Do you think drilling holes in the aluminum engine mount would cause any possible problems? Given of course I'm careful when drilling the holes. Would I weaken the transom mount any? I can't think of anything worse it'll do other than adding a few more holes where holes already exist right? <br />I get a little nervous modifying things like an outboard

 

[boatster]

Re: Aluminum to Stainless. Which Prop? I have all stats listed Avon Rib 50 hp...

Re: Aluminum to Stainless. Which Prop? I have all stats listed Avon Rib 50 hp...

HI Walleyehed,<br /><br />I'm about to buy the Michigan Wheel 14pitch Raptor prop from here on Iboats. Do you think this would be a good prop?

 

[walleyehed]

Re: Aluminum to Stainless. Which Prop? I have all stats listed Avon Rib 50 hp...

Re: Aluminum to Stainless. Which Prop? I have all stats listed Avon Rib 50 hp...

I think it would be just fine...The Rapture series is being replaced by a simular design with a bit different blade features. They just have a close-out price on the existing props in stock.

 

[boatster]

Re: Aluminum to Stainless. Which Prop? I have all stats listed Avon Rib 50 hp...

Re: Aluminum to Stainless. Which Prop? I have all stats listed Avon Rib 50 hp...

Thanks again Walleyehed.<br /><br />I'm going to order that prop and raise my motor at least 3/4" and go from there. I'll report my findings.<br /><br />Boatster