1964/65 Evinrude 40hp Big Twin

[USMC1989]

Hey Guys-
I recently purchased a 1964 Mirrocraft runabout that I am turning into a fishing boat. The boat is aluminum and 14' long, 62" wide at the transom. The motor that came with the boat is the original 1964/65 Evinrude 40hp Big Twin. I am going to have the motor professionally gone through over the winter to make sure it is running A1. My question is this - what kind of top speed can I expect to get with this motor, on this size boat? Other than installing a new floor, & a few seats, there won't be much weight to the boat (it's pretty bare as it sits).

Any info/opinions would be much appreciated.

Thank You-

Brent Stinebaugh
Mukwonago, WI

 

[nwcove]

Re: 1964/65 Evinrude 40hp Big Twin

i would guess 18-22 mph. maybe a bit more if the boat is really light.

 

[lindy46]

Re: 1964/65 Evinrude 40hp Big Twin

Well, my 14' Glasspar runabout with a 40hp evinrude did 33-34mph, so I'd expect at least that from an aluminum boat.

 

[steelespike]

Re: 1964/65 Evinrude 40hp Big Twin

Actually many times a glass boat will be faster than a similar size aluminum Due to the usually smoother less convoluted
bottom. If the 40 can twist a 14" prop up to 5,000 rpm the speed would be 34.
Its unlikely a 14 would work for you but get your wot rpm and gps speed along with the prop size
and let us know the results.

 

[kfa4303]

Re: 1964/65 Evinrude 40hp Big Twin

I'd guess around 25-30 mph too, but the big ol' 40 should have lots of low end torque.

 

[USMC1989]

Re: 1964/65 Evinrude 40hp Big Twin

The guy I bought it from said he had clocked it at 20mph WOT on gps. That seemed low to me, I would have thought that a 40hp Big Twin would get it going closer to 30mph. How much difference does the prop make? The prop currently on it is a bit chewed up, I will be replacing it. Looking at a few different prop manufacturers, it appears that there are two standard props for this motor (10-3/8" x 11" pitch and 10-1/2" x 12" pitch). I found one other that is 10-1/2" x 13" pitch, I'm thinking that this one would likely increase the top speed, but wonder if it would bog down the motor too much......

 

[Chinewalker]

Re: 1964/65 Evinrude 40hp Big Twin

If you didn't add all the floors, etc. then the 13 might work fine, but with the added weight of your conversion, a 12 or 11 would probably work better. Wouldn't hurt to grab several different ones if you can and try them all... Never hurts to have a spare prop (or two). Even if one isn't a great performer, it can get you home in a pinch if your primary one leaves a blade on a rock...

 

[kfa4303]

Re: 1964/65 Evinrude 40hp Big Twin

yeah, 20 mph seems a little lowish :/, but a lot depends on the total load and weight distribution. Hopefully, it will run better once its been tuned up. Here are some links to vids of motors like yours running on the open water to give you a comparison. What your motor may lack in top end speed it will make up for in low end torque. You should be able to pull an elephant up onto skis once its running right. Keep us posted.

1960 Evinrude 40 HP Outboard - YouTube

1965 Glassmaster runabout with 40 Hp Big Twin Evinrude Outboard - YouTube

1962 Evinrude 40 horsepower lark iv - YouTube

 

[USMC1989]

Re: 1964/65 Evinrude 40hp Big Twin

Excellent, thanks for the input guys.