I would just like to share my delight at the propellor i have just purchased. As some of you may know I was interested in getting the most out of my tohatsu 50hp as I could to allow me to wakeboard in addition to just having a well set up outboard. Getting the right prop for our boats (26x in my case) could be an expensive 'trial and error' kind of job. I found the prop I now have on by accident on YouTube whilst looking at prop setup. It is a 'Propulse' propellor. The beauty of it is that the pitch of the blades can be adjusted, allowing the user to play with effectively 5 different pitches until they are happy. In addition, the blades are composite so very strong and replaceable if you do have an argument with a reef. In our boats which some regularly beach, I can't help but think this is a good thing. Well, sea trials started in Ernest last weekend and this morning (in moderate sea state), I achieved 17.4mph max speed by my instruments. Incidentally, I have no connection to this product. I just hope it will help someone in the same situation as I was. Happy motoring!
Fri, 08/07/2016 - 11:11am
#1
james.brine
Propulse propellors
Hi James
Thanks for this, very interesting. I thought maybe one of these might be expensive, but they seem about the same price as a regular ali prop, which is useful.
The only thing that surprises me is the pitch is quite high, typically 11" upwards. My experience of both 26X and 19 is that 11" is about the maximum pitch you need, anything over that and you can't reach peak revs at WOT. Macs are a lot heavier than the kind of boat 50HPs are mainly intended for. It's a shame you can't get them down to 10" or even 9" pitch. Also, a 4-blade prop is usually regarded as behaving like a 3-blade one pitch higher (e.g. 11" 4-blade is similar to 12" 3-blade).
About what pitch have you found to be the ideal, and what peak revs does it give you? Is your engine an older 2-stroke or a modern TLDI?
I have a new Tohatsu 50HP TLDI on my 19, with a 12" prop, and I barely get 5000 RPM even on the plane (and the 19 does actually plane!). I've been thinking of getting an 11", but an adjustable one is a great idea. I just think I'd probably end up with it at 11" anyway and be unable to make use of the range of adjustment.
Still, replaceable blades are a bonus!
Rick Jones (Treasurer), former 26X & 19 owner, Isle of Wight
Hi Rick. I have ended up on the highest setting (where the blades are the most flat). Sorry, still learning prop terminology. I didn't get a good look at the revs as it was quite an intense experience keeping her in a straight line! Today was first successful outing but I'll get more info up here as I progress. My engine is the M50D I think which is the older one I believe.
Hi James
Blades at their flattest is the lowest pitch, which is 11" according to the data I found. To understand prop pitch, think of the blades as part of a screw thread, then imagine continuing that thread for a full 360 deg around the hub. The distance along from one turn to the next is the pitch, usually expressed in inches.
Changing pitch is like changing gear in a car. Too low a gear/pitch and you'll over-rev before reaching full speed. Too high and the engine will labour, and not provide enough thrust to reach full speed. As with a car, the optimum depends mainly on the ratio between the power of the engine and the weight of the boat. The sweet spot to aim for is the engine to run at the revs that deliver max power (typically around 5,500, the manual will say specifically) with the throttle on full (Wide Open Throttle - WOT) and the boat running at full speed in calm conditions.
As weight is a big factor, the amount of gear carried and the number of people on board can make a big difference to the performance and optimum settings.
The M50D is, as you say, the older conventional 2-stroke. The modern injected TLDI is also known as the MD50 - confusing!
Rick Jones (Treasurer), former 26X & 19 owner, Isle of Wight
Hi James would you like to take a photo of it and send it to me for the magazine?? Then non-internet users can see it?
Liz
I'll see what I can do Liz.
Thanks!
I have no experience of 'Propulse' props.
I did fall in love with a Kiwi prop once but luckily never bought one as they had all sorts of problems. They were the same nylon type.
Just a thought.
Chris
I have the pro pulse prop fitted to my 26X. It is pretty good but I am not achieving the same as the OP.
Best speed is 16mph through the water without ballast and 2 people. I have the a Yamaha 50 4 stroke. The engine only revs to 4100rpm at wot. The prop is set at the minimum pitch it adjusts to which is probably not quite fine enough.
When I bought my 26X it had a Suzuki 2-stroke with the stock prop, 13" pitch I think, which was far too high. I replaced it with a 4-blade 9" which was about right (I think the Suzuki's shaft speed was a bit higher than most other engines too).
Eventually I bought a new engine (the Suzuki was persistently troublesome), a Tohatsu TLDI, which I think I ordered with a 10" prop. It did over-rev a bit at WOT, although I almost never drove it flat out. An 11" would probably have under-reved slightly. If you're not worried about optimising max. power it's also worth noting that a lower pitch gives you better control at low speeds, and a less sensitive throttle at cruising speeds.
So in my experience, a 26 is likely to be best with a 9" or 10" pitch prop. If very lightly loaded then you may be fine with 11". This is assuming a 50HP engine, with 60HP you could maybe go an inch higher, on the assumption that the 60 would increase top speed by about 10%.
Rick Jones (Treasurer), former 26X & 19 owner, Isle of Wight
Hmm. yes. Rick it seems you might be right. After my initial elation with the max speed I achieved, It may have been a bit of a fluke. I was motoring in a swell single handed when I achieved 17.4mph so my have been surfing down a wave at that point. It was also after having adjusted the prop from its highest pitch so you can imagine the improvement I felt. After going round Land's end and over to St Michael's Mount last weekend, doing a longer stint in better conditions, it seems to me that I an still a little over-propped. It still achieves about 16mph occasionally with everything trimmed perfectly but not consistently. Macs seem to always be 'nearly' on the plane and drop and raise speed over waves. Do you remember what speed you achieved with the 9"? Blue water yachts recommend the 10" :and I guess they should know: and if a 9" runs the risk of over-revving I think I'd better avoid. By your advice, I'm still effectively on a 12" pitch so a 10" would be another two steps closer to where I want to be. I may invest in a 10" but keep the Propulse as I do have good control with it and the additional comfort of repairable blades (a must if I do the Avon again!). Finally, I may add some hydrofoils to get her bum out the water a bit better. Anyone tried these?