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  13' Whaler, 50hp Yamaha, Prop size????

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Author Topic:   13' Whaler, 50hp Yamaha, Prop size????
Scott AussieWhaler posted 06-13-2003 11:18 PM ET (US)   Profile for Scott AussieWhaler  
Hi everyone,
I was wondering if I could get some advice from other members of the board who perhaps have had a lot more experience than myself with boat, motor, prop combinations. On my 13' whaler at the moment I have 96 50hp Yamaha with a polished and cupped ss prop 11 1/8" x 13" which is returning around 30 knots (34.5 mph) at about 5150 - 5200 rpm. I have read a couple of the other strings and the motor is about the right height (cav plate 1/2 - 3/4" above the bottom of the hull). I believe that this motor has a recommended rev range between 4500-5500. Anyway, I was wondering what other owners are running in the way of props on their rigs with similar combinations, could you also please include the diameter as well as the pitch of the prop you run and if it is a Yamaha 50 hp outboard what revs are you getting. I was thinking of trying to obtain a smaller diameter but perhaps the same or greater pitch propeller for this motor (10 1/2" x 13", 10 1/2" x 14 or 15") to increase the revs and to maximise speed at WOT. However, stainless prop availability is somewhat limited here in Australia so some feedback before I order something from America would be most welcome.
Scott Natho
timbo posted 06-14-2003 10:12 PM ET (US)     Profile for timbo  Send Email to timbo     
I have a 73 13' with a 93 40 yamaha and i get about 40 mph give or take with the factory prop.. this with me and 6 gallon tank and a battery, this is wot. I haev no idea as to what kind of rpms i am running at, the throttle is loose so i let it back down to cruising speed, with a 50 i think you should at least be getting somewhere in the 35 and up range mph wise. Hope you found this usefull
Scott AussieWhaler posted 06-15-2003 03:33 AM ET (US)     Profile for Scott AussieWhaler    
Hi timbo,
Thanks for your reply, I should've added that the boat has been fitted out for bassfishing including forward casting deck, livewells, bow mount minnkota and a 130 amphr battery up front so it probably weighs more than most 13's. Do you know what size prop you are running, pitch, diameter and alloy vs ssteel? Thanks once again for your reply.
Scott Natho
FISHNFF posted 06-15-2003 10:08 PM ET (US)     Profile for FISHNFF  Send Email to FISHNFF     
I had a 1981 Sport 13 with front bench removed. With a bow mount trolling motor, group 30 battery, bait tank, and me alone with a 1991 50 Yamaha on the back with a 15" Yamaha SS prop turning 5400RPM, it would see an honest 40MPH plus per GPS, a headwind trimmed to the max. With two onboard it would do 38. In saltwater alone without the trolling motor, extra battery, and bait tank, it really moved. Can't remember how fast or what RPM, but almost scary. Mounted two holes up.


elaelap posted 06-16-2003 02:27 AM ET (US)     Profile for elaelap  Send Email to elaelap     

I've got a Yamaha 50 hp 4 stroke High Thrust (like a "Bigfoot") on my 16/17 Katama with a 13 pitch prop and get 30.5 mph at 5900 RPM WOT in perfect conditions. My cavitation plate is at the exact level of my boat's "keel," and I slapped two coats of ablative bottom paint on her this past winter. Those numbers are with me (200 lbs) and my 165 lb son aboard, 12 gallons of gas, and 30-40 lbs of lead weights in the bow locker.

Dick, a frequent contributor here, gets 34-35 mph out of his 50 hp motor on his newer Montauk (1999, I think), a heavier boat than mine, I believe.

I'm anything but an expert, but it seems that you should be getting more speed out of your rig.


Scott AussieWhaler posted 06-16-2003 05:18 AM ET (US)     Profile for Scott AussieWhaler    
Hi everyone,
Thanks for your replies. Yes I think that perhaps I should be getting slightly higher turns out of the motor but then again around 35 mph is plenty fast. I am more worried about the motor longevity than top end speed to be honest. I would rather go about the same speed but the motor turning around 5400 or 5500 rpm and not labouring, so I was thinking that my 13" prop maybe too wide in diameter and that it might pay to drop down from the current 11 1/8" to 10 1/2" in diameter to free the motor up. So I was wondering fishnff and elaelap what was the diamter of you props? Thanks again for your replies I have found this site to be a wealth of information, especially for someone not based in the US. I have learnt a lot from reading the strings about boat setup, performance and oils, maintenance, etc. over the last 6 months, much more in some instances than spending a fair part of my life around boats.
Scott Natho
OutrageMan posted 06-16-2003 07:23 AM ET (US)     Profile for OutrageMan  Send Email to OutrageMan     
I have a 1997 13' Dauntless with a 50hp 4 stroke Yamaha. I just put a 13" pitch Mercury Trophy Sport 4 blade stainless prop on it. Works very well, but I think I should have gone for the 12"


Over the LINE posted 06-16-2003 08:56 AM ET (US)     Profile for Over the LINE  Send Email to Over the LINE     
I have a '84 13' with a 2003 Yamaha 50hp. I tried several props before I settled on a Yamaha 10-1/4 x 15 SS. I run 5400 rpm over 40 mph with 15 gallons of fuel (fuel tank under forward seat), me (185#) and a small ice chest. Because of the extra stuff on your boat, I would probally go with the 10-1/4 x 14 version. The aftermarket props did not work out for me at all.

Good Luck

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