150 Montauk 60-HP: Four-blade Propeller

[Dutchman]

[My 2008 Boston Whaler MONTAUK 150 with Mercury 60-HP BIGFOOT ELPT outboard engine] boat is on the hard for the winter season. Christmas is coming up soon, and I want a new propeller from the kids. Two days ago on glass-like water with a light load--only a extra 300 lbs over dry weight--running at full throttle produced these great results:

RATIO = 2.33:1
ENGINE SPEED = 5,950-RPM
BOAT SPEED = 36.8-MPH (32-nautical-miles-per-hour)
PROPELLER PITCH = [later revealed to be 14-pitch]
PROPELLER MODEL = VENGEANCE three-blade PN 48-17314, the OEM propeller

I like the top end boat speed but hate my [acceleration from a standing start onto plane]. I like to go with a four-blade stainless steel propeller for better acceleration and will be happy with a top boat speed of 34.5-MPH or 32-nautical-miles-per-hour.

Please advise what propeller to ask from from Santa.

[jimh]

What is the rated pitch of the propeller used in your test reported above?

Try a four-blade propeller from the same manufacturer with the pitch reduced 1-inch.

For a Mercury VENGEANCE, the equivalent four-blade would probably be found in the VENSURA series. It looks like it is made only in a limited number of pitches.

I wouldn't invest in any propeller without having the option to return it and exchange at no cost for a different model. You cannot really predict exactly how a propeller will run with a particular boat and engine. I wouldn't want you get get stuck with a $450 paper weight for a present.

[macfam]

That Vengeance prop is 14-pitch.

One other note: I believe that Quicksilver brand are identical to Mercury propellers as far as metal quality and design. They don't have the fancy name recessed into the propeller, but otherwise are equal. According to my research, substantially less money.

[jimh]

I think you are going to have trouble finding a four-blade stainless steel propeller with a pitch as low as 14-pitch. The VENSURA propeller only comes in pitches of 17, 19, 21, and 23. Since you are presently running a 14-pitch, there is little chance you could turn a 17-pitch VENSURA four-blade.

[Dutchman]

Jim first thanks for cleaning the post up.

Yes the OEM prop is 3 bladed 13-3/8" diam. with 14" pitch.
Mercury tells me I can go with a SS Spitfire X7 prop 13-1/2"x15 (P/N 8M0055548) not inexpensive.
As Jim mentioned I don't want a $450+ paper weight and the prop is not heavy enough for an anchor.

Here in Michigan it is nearly impossible to try a prop plus if I buy at the dealer I'm looking at another $150 to $200 more.

Based on that I thought what about an Aluminum 4-bladed Spitfire 12-1/2" x 19 or 13-1/2" x 15 or a 13" x 17" prop.
These are a third the price of the SS and a quarter the price of a Vensura. These Spitfire P/N are 8M8026580, 590 or 600.

[jimh]

I am not familiar with the Mercury SPITFIRE line of aluminum four-blade propellers, but since they are available in a very wide range of low pitches, 10-11-12-13-14-15, there should be one that is just right for your 60-HP application.

Compare at: https://www.mercurymarine.com/en/us/pro ... /spitfire/

[macfam]

Just read a news release on the Spitfire X7 four-blade, made from Mercury's special alloy The lowest pitch is 15".
I can't imagine that we could go from the Vengeance three-blade 14" pitch, to a four-blade 15" without dropping significant RPM.
Got to double check to see if I can raise the engine a hole or two. Perhaps then it could be an option on our Montauk 150 boats.
http://www.boatingindustry.com/news/2015/11/04/mercury-marine-introduces-spitfire-x7-propeller/

[flymo]

I am not really clear on why you want a four-blade propeller, as opposed to just dropping pitch to get better acceleration. I had the impression that four-blade propellers were for better grip and heavy loads, not for improved acceleration. In fact, I would have thought that in your situation of a relatively underpowered hull with a large propeller diameter that the increased blade area on a four-blade would tend to make things worse, not better.

You might be interested in contacting Power Tech Propellers. They have an extensive selection of stainless propellers, and their recommendation for my situation has me very happy. I used their contact form and had an answer within a day. Your situation sounds somewhat similar to mine (F70 on a classic 15-footer) in that you have a large propeller spun by a four-stroke-cycle engine, which tends to make power higher in the RPM band. If that is truly the case, a propeller with less blade area might get the nod. I went with a Power Tech SCD3 and the improvement in performance was nothing short of stunning.

Power Tech will allow you to swap for a different prop for a fairly nominal fee, and their pricing is very competitive. They do not sell direct to the public. After getting their recommendation I bought via Dan's Discount Props.

Tim

[Jefecinco]

Consider consulting with the folks (Ken) at http://www.propgods.com for a good propeller choice for your 150 Montauk. They loan propellers out for testing in their general area but I doubt you want to go to Florida to take advantage of that. They may offer an exchange program for long distance customers with some kind of deposit. I think they are worth a look or a call.

[Dutchman]

I did talk to several prop guys, including Ken, and he advised that I have my current 3-bladed prop tuned slightly differently. He uses a guy in his area (Sarasota) that could change the cup, pitch, and leading edges slightly on my 3 blade Vengeance to get me the results I'm looking for. Good offer, good price, [less than] $100, but I have to ship it all the way to Florida and back. I still like the idea of having spare prop and sending the only one in to get tuned keeps me out of the water. I never had a boat that didn't have at least one spare prop.

Yes, my little boat is under powered, especially for as heavy it is, hence I was thinking four-blade. Ken said I could try a Powertech SCD4 4 bladed 13 x 14 all SS.

Again my problem is with buying and not getting the results, but I did find a local outlet that seems to have a decent return policy. Now I have to wait until next year when the water isn't solid any longer here and the boat back out of winter storage.

[flymo]

Just based on my own experience with the F70, I would NOT recommend a 4-bladed prop. You want less blade area, not more, to allow the prop to spin up faster, into the motor's high RPM where it makes its power. I am very happy with the SCD3 on my F70 and I would recommend trying that first.

A heavy boat with plenty of power would be fine with a 4-blade. Of course you never know until you try!

Tim

[Dutchman]

Flymo thank you but I don't have a Yamaha F70 four-stroke-cycle engine. I have the Mercury 60-HP Bigfoot which originally was designed for pushing pontoon boats due to the stronger and larger gear and gear ratio. It will get to the RPM in the same time if I keep the pitch close.

[macfam]

Next week, I plan on taking my 13-3/8 x 14 Mercury VENGEANCE stainless steel propeller to H & H Propeller in Salem, Massachusets for some minor repairs. I'll inquire about that SCDS four-blade SS from PowerTech. I can't wait to hear if anybody has tried one.

[flymo]

It will get to the RPM in the same time if I keep the pitch close.

No, it really won't - there's more to propeller design than pitch.

I am well aware that you have a Mercury Bigfoot, which has the larger gearcase and different gear ratio compared to the regular Mercury 60 (as does the Yamaha F70, compared to the F60). In my search for the correct propeller, I was using a 3-blade propeller with a lot of blade area. I dropped all the way down to a 13-pitch in that propeller, and even though I was significantly under-propped and ran out of RPM on the top end, it did not accelerate anywhere near as well as the SCD3 does in a 16-pitch. I am convinced that the reduced blade area is advantageous for 4-stroke-cycle engines that naturally have less low-end torque, which is why I am advocating being careful about adding blade area when you are looking to improve acceleration.

Don't mean to be harassing you, just trying to save you some time and trouble. The SCD3 was a revelation to me. I can't tell you what a difference it made, and I want you to have the same experience.

Tim

[Dutchman]

Tim thank you for the explanation you aren't harassing me it is my ignorance regarding the F70 which I thought was just a 70 HP 4-stroke like a standard 60 HP 4-stroke. What was the diameter & pitch you ended up with?
I will add this SCD3 on my list of possibilities.

[flymo]

Yes, it's a bit confusing. Up through 60 horses, Yamaha's "F" designation denotes the smaller gearcase, and "T" refers to the intermediate gearcase. At 70 horses, they only offer the intermediate gearcase, so the F70 has the same gearcase and gear ratio as the T60, while the F60 uses the smaller gearcase which has a different ratio.

I am running a 13 x 16 Power Tech SCD3, and am slightly underpropped - if I were to run light a lot I would want an inch or two more pitch.

Of course your Merc may have a different power curve than my motor, but I'd be very hesitant to put a 4-blade on there - I have the general impression that 4-blades are for heavy boats with plenty of power, that are looking for more grip on the water. I think that's different from your situation.

Tim

[Dutchman]

Thank you Tim
My boat is what I think heavy for a 15' boat. My normal running is as follows;
Boat itself with bow rail & Bimini top = 1000lbs
Mercury 60hp Bigfoot with battery = 310lbs
12 gallons of gasoline = 72lbs
Admiral and me = 430lbs
Cooler with lunch/drinks = 35lbs
Safety equipment for 6 and Danforth anchor + rode/chain = 83lbs
Lines fenders, etc. = 25lbs
Adding this up I'm looking at 1,955 lbs that my prop has to push through (preferably on top) the water for a standard outing.
We quite often have another couple with us, add another 320lbs or when we go tubing I pull a Rockin'Mable 2 person tube with one or two people on it. Quite often these 2 are my adult sons adding an additional 400-450 lbs.
Bottom line I'm looking at pushing close to 2,500 lbs, hence I like more power out of the OB which can only be achieved via a propeller change.