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OK I finally used my x-mas gift card from the sons to get a 4-bladed prop and did some un-scientific comparison.
I used stopwatch and GPS. 13 gallons of gas, my standard equipped boat with motor weighing in at about 1,275 lbs plus 270 lbs of crew for an approx. total of 1,625 lbs.
The original set up on my 2008 Montauk 150 is the Mercury 60HP Bigfoot with a Vengeance 3-bladed Stainless prop. (Merc 48-17314 (13-3/8"x 14) a great standard setup except no whole shot.
(WOT] of 34.7 mph and 9.1 sec to plane.
Picked up a Mercalloy Spitfire 4-bladed aluminum 13x15 prop and tried it (actual 12.8 x 15 P/N 48-8M8026580) . Had hole shot that was better but couldn't get it over 5,200 rpm no matter how I trimmed. Hence not the right prop.
I exchanged it for a the same kind 13.8" x 13" pitch and that is the right prop (48-8M8026570) . I have to make sure the trim is 0 (all the way in) and she gets on plane in around 6.7 sec. I can trim her out to get my 5,900-6,000 rpm (takes slightly longer than with the Vengeance) and top out at about 31 mph. Also she is more prone to porpoise at the top end but 25 is fast enough I'm not racing anybody just putting around inland lakes.
Bottom line I did get a better whole shot even with another 165 lbs weight, which is what I was after.
We'll find out if she also pulls the towable better when we get some better weekend weather here in West Michigan (you know how it goes nice during the week and rain on the weekends)
Happy boating
Edited by Phil T on 06/10/16 - 7:32 AM
Skipper E-J
m/v "Clumsy Cleat" a 2008 Montauk 150
To regain that top speed, what you probably want is the brand new SS Spitfire X7 4-blade, made from the same material as the larger Enertia. It is supposed to be the fastest prop you can buy for the Bigfoot gearcase.
Interesting data. It's a little bit hard to tell what's going on there, as you were varying both pitch and blade area. Your original 3-blade presumably had less blade area than the 4-blade props, yet was slow to plane - I can't figure out what would cause that combination of symptoms. In general, I would have thought that a 4-blade prop is exactly what you don't want on a "not overpowered" boat, especially with a 4-stroke that makes its horses well up in the RPM range.
You may want to consider another tack, that being less blade area (meaning back to a 3-blade) and lower rake to increase stern lift. I followed that path with my F70 on my 15 and ended up with a PowerTech SCD3, which is a semi-cleaver, low rake design - the results were dramatic (in a good way).
I don't know what the corresponding prop would be in the Merc lineup, if you are interested in staying with the Merc brand; perhaps Finnegan can advise.
If you are fine tuning your prop selection for performance, you can't select an aluminum prop. Just not going to cut it.
I surmise you are trying to improve your time to plane but not necessarily WOT speed?
Given the low horsepower to weight ratio, and the shallow power curve of the 4 stroke motor, I would agree with Tim, you need to increase the RPM's in the lower end.
When testing props, you need to test in the same make and model and then change size. Prop performance is NOT universal across models or even brands or materials.
Said another way, a 13.25x17 X brand aluminum prop is different than 13.25x17 X brand stainless steel and different than a Y brand 13.25x17 stainless steel prop.
Finnegan in answer to your posting yes I'm aware the X7 would be better but also a lot more expensive, and yes I did see the videos on the Merc site, hence that is why I selected the inexpensive Spitfire aluminum.
If I win the lottery I would buy a bunch and try them all to determine the best prop for what I want to do, but if I win the lottery I wouldn't be using a Montauk 150.
Yes I do agree with Tim too but I have explained somewhere B-4 here in West Michigan they don't let you try props (I was able to return my first selection because "I didn't use it" and was told by somebody it wasn't the correct selection) You buy and if it doesn't work re-sell at a tremendous loss which can be very expensive if you want to try 3 or 4 props.
Also if buying from a dealer they want to sell only the prop brand like your OB.
Yes Phil I'm not at all looking for top speed 90% of the lakes we boat on are too small to run WOT for more than 3-5 minutes or too busy to do that.
Phil I was after quicker hole shot and yes I know a 2-stroke does that better but this aluminum inexpensive 4-bladed prop seems to do the trick for me.
I'm happy and when not having a full boat or doing any water sports I have a great SS prop on withing 5 minutes.
Also if buying from a dealer they want to sell only the prop brand like your OB.
You are going to the wrong dealer. My local Whaler dealer's Parts department was happy to sell me any prop I wanted. Not the most competitive with their prices.
Many people are looking at propellers and stunned they are expensive. Keep in mind it is the second most important element after the engine.
Do you have postal service in west Michigan? If you do, there are many prop sellers that can MAIL you any prop you want to try. They also usually have MUCH better pricing than the locals. If you don't like the performance from the prop you try, you just send it back and try another. The people that do business in this way are usually more knowledgeable about how to proceed in your trials to achieve the particular result you are looking for than forum posters.
I have NEVER purchased or even tried a prop that wasn't sent to me via UPS or the U S Postal service.
E-J, finding the right prop can be a lengthy process. The prop I ended up with is the fifth one I tried. I always bought online, mostly from Dan's Discount Props, and I resold the ones that didn't work, right here at WC. I mostly got within $20 or so of the original price. The whole process took some time and effort, but not a ton of money. I'm sure the total I spent was less than the dealer price on one of those 4-blade stainless jobs!
If you found one that works for you, that's great! If you want to keep working to optimize, I can heartily recommend PowerTech props. They make a bunch of different styles in 1" pitch increments, quality is great, made in the USA, good pricing, and their customer service was very helpful to me in finding the right style prop.
Tim
PS: I may not be quite done with my prop search - might want to bump up an inch in pitch.
Also if buying from a dealer they want to sell only the prop brand like your OB.
You are going to the wrong dealer. My local Whaler dealer's Parts department was happy to sell me any prop I wanted. Not the most competitive with their prices.
I was looking for an inexpensive solution to a [u]slight[u/] problem I had. There are many good outlets on the internet that can help you in selecting and selling a prop. Secondly I had a gift card to a specific marine store outlet, therefore was forced to buy there. I really didn't need anything else for the little boat and therefore thought I'll try an inexpensive prop for better hole-shot.
Phil/Silentpardner you are right, but again I state I'm in an area where the marine dealer has approx 4 months to get their moneys worth. If you just walk in and didn't buy an engine or a boat from them they don't service you, when just part buying, like they do "down South" or in the Southwest or Southeast.
I was able to get a better hole-shot without out of pocket expenses, are there better props, yes there are, would they cost me money or a lot more money, yes they would.
I have a great good all around all Stainless Steel Vengeance prop which is fine.
I just wanted to let people know what they can expect when making a change or looking for what I did.
When for what ever reason I need to replace my Vengeance I will use an internet supplier or have the SS prop reworked, but until then I'm happy with my $160 solution and being able to switch between both props in a coulpe of minutes. Used the Vengeance this weekend on the big Lake Michigan. Will use the 4-blade next time I'm pulling Rocking Mable behind the boat which might not be soon with water temperatures still in the low sixties.
