BoatBanter.com - View Single Post - 1976 Boston Whaler Re-power Question

Larry[_4_]

wrote:
On Thu, 04 Mar 2010 19:48:08 -0500, wrote:

I made the exact same repower on my boat (Mariner 75 2S to 60 4S Big
Foot)
The weight was close but the prop had to be changed (does he need a
15p, I have one in SS, make offer)
The tach is a 2 wire hookup from the gray wire to ground (port side of
motor) and you could certainly do this temporarily if he can borrow a
tach.
This actually picks up the unrectified output of the charge windings
but there is also an output from the computer. (there are 2 gray wires
on the motor). They both seem to work the same on my motor.
If you just had a meter with a frequency counter you could interpolate
that with a little simple math. Use the idle speed as a sanity check
(700 or so) then see what WOT works out to. You have a pretty wide
"acceptable" range.5500-6000 with the rated HP right in the middle.
I would shoot for close to 6000 with the boat empty. It will always
get heavier as time goes by. ;-)

It's not the Big Foot so he may not be able to take you up on your
offer, but I will pass it on. Good point on the max RPM's. I doubt his
old Mariner has a 6000 RPM redline.

If it is not a big foot he won't be using his old prop either. The big
foot is a 14" prop, same as the 75 Mariner.. The non-bigfoot one is
12 1/2".

Neither has the Big Foot gear case.