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  Prop: Montauk: Mercury 4-stroke 60-HP Bigfoot

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Author Topic:   Prop: Montauk: Mercury 4-stroke 60-HP Bigfoot
mbking1 posted 06-01-2002 11:39 AM ET (US)   Profile for mbking1   Send Email to mbking1  
I am appx 10 mph under expectations at WOT. Currently, I have an alum prop that Marina suggested. max speed per GPS is 29mph at 5700rpm. I have a Doel fin, so I expect some reduction,but not this much. I am considering one of the new high tech SS props and would appreciate any thoughts so I can make the correct prop choice. Thanks Mark
JBCornwell posted 06-01-2002 11:58 AM ET (US)     Profile for JBCornwell  Send Email to JBCornwell     
Hey, Mark.

Who in the world talked you into putting a Bigfoot on a Montauk? With that big gearcase you wont approach 39mph. That gearcase is intended for 'toons and displacement boats!

With 4" setback, SE Sport 300 fin, SS 18" prop and a clean bottom my Montauk can make 38.5 with a Suzi DF70.

With a high speed gearcase your EFI 60 calculates to 32.6 at WOT and at the same weight as my Montauk (1800, on the water). I would expect the drag of that truck gearcase to subtract at least 3mph from that figure.

I think you are getting what that engine can deliver, and have the right prop for it.

Red sky at night. . .
JB :)

mbking1 posted 06-01-2002 12:28 PM ET (US)     Profile for mbking1  Send Email to mbking1     
JB:

Thanks. I appreciate your input a lot. I love the 60 and its fuel efficiency. Im not a speed fan anyway. I was just wondering if I would pick anything meaningful with one of the SS high tech props. Thanks again. Mark

Dick posted 06-01-2002 03:46 PM ET (US)     Profile for Dick  Send Email to Dick     
JB hit the nail right on the head, you are getting all that Big Foot can deliver. I don't thing an SS prop will give you anymore.
I can squeak about 33 out of my Montauk with the Merc 4stk 50 and standard gearcase, I tried an SS prop and didn't get enough improvement to justify the cost.
mbking1 posted 06-01-2002 09:32 PM ET (US)     Profile for mbking1  Send Email to mbking1     
Thanks Dick:

I think you just saved me $400. Mark

jimh posted 06-02-2002 08:27 AM ET (US)     Profile for jimh  Send Email to jimh     
[Rewrote topic--jimh.]
dscew posted 06-03-2002 06:44 PM ET (US)     Profile for dscew    
It would seem to me that a steeper propeller pitch may make up for the limits that the lower gear ratio in the bigfoot lower unit gives you. All things being equal, if the higher gear ratio has a 18 pitch, then a lower ration should be able to use a 19 without a loss in low end performance. Talk to your dealer.
Dr T posted 06-03-2002 09:46 PM ET (US)     Profile for Dr T  Send Email to Dr T     
Intuitively, dscrew has a good point.

As JB points out, the Bigfoot is made for pushing big heavy loads around at moderate speeds. When the load is light, it still pushes you around at moderate speeds, but is only very lightly stressed. In a standard configuration, you ought to be able to pull a lot of waterskiers at the same time.

dscrews point is that you can trade one gear ratio (the lower unit) for another gear ratio (the pitch of the screw). You can do this until you run out of torque. Testing, however, is needed to determine where that point is. It took me three props to figure it out for 5000+ ft altitude on a 13 Sport with an 82 Johnson 35 hp.

As they say in the ads, your milage will vary.

tds

lhg posted 06-03-2002 10:58 PM ET (US)     Profile for lhg    
I would mount the engine in the middle (3rd) bolt holes, effectively lifting it 1 1/2". You have nothing to loose by trying this out.

This will accomplish two things. Eliminate the planing drag of the Doel Fin stern lifter (this is considerable), so that it rides clear of the water when planing, where it's not needed. The higher engine height will also reduce gearcase drag.
An SS Prop will probably be required, however. If you do this, try your aluminum first, but be sure you're not overrevving.

The 4 1/4" Big Foot gearcase is the same size used by the Yamaha and Suzuki 70's, so I doubt if that's your real problem. And the engine is almost as powerful, at least as much as the Yamaha 70.

Assuming the boat is not heavily loaded, I would assume it should do about 36-38 with the 60.

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