Pair of Martin 75s

[amuller]

This past weekend I picked up two Martin 75s, something I’d been looking for.

But I had not realized that there are at least two versions of these. In the "TS" version the twist grip shifts the motor (neutral shift) and the red button on the end pushes it down to a fast idle. Thus, I presume, "Twist Shift."

In the "ST" version the twist grip is connected to the throttle, or the timing, or both. Thus, "Syncro Twist."

The two I got are the TS version but the manuals I find online seem to be for the ST version.

Have I got this figured out correctly?

Also, Martin calls for a 10-1 fuel mix. Is this what people are actually using these days?

am

[frankr]

You got it figured out correctly. TS and ST

The oil war is still going on.

[The Boat House]

hiram1914 & Buccaneer posted these for me.
Very helpful going through the one I did.
I’ll be running 3 oz. per gal. (little richer than 50 to 1)
in it this summer. The 40W oil for the lower unit is
very hard to find.

http://aomci.org/forum/viewtopic.php?f=2&t=15742&start=10

http://aomci.org/forum/viewtopic.php?f=2&t=15742

[amuller]

Thanks very much! Definitely some interesting design elements in these motors.

Eska also used a tabbed-spring neutral clutch but it was above the pump, so I doubt prolonged idling was wise.

40W motor oil?? Never seen that. SAE 85 gear oil would be roughly similar in viscosity to SAE 40 motor oil.

Anyone know of impeller dimensions/interchanges for these motors?

You are going to use 3 oz/gal when Martin calls for 12?

[The Boat House]

Russ will what have ever you need but contact him before
ordering as some prices are incorrect . He is also
willing to answer any questions you may have. Always
replied to emails the next day.
https://martinoutboards.com/
I initially tried SAE 85 gear oil but the clutches seemed to slip.
Russ may have the 40W. I got some from a member.
I would suggest 30W if you cant get the 40W.
I have run 3 oz. gal. in most everything I have for years.
Sending you a PM.

[Buccaneer]

https://www.agrisupply.com/premium-non- … l/p/28785/
Only $2.99 per quart

Prepare to be boarded!

[amuller]

Hmmmm 40 is different from 40W, meaning winter grade. The description doesn’t seem to match the pic.

i can envision that gear oil, with heavy anti-friction additives, might make those clutches slip. I think this arises with motor bikes with wet clutches.

Alan

[Buccaneer]

I was thinking the "W" meant weight.
Either way, not a good idea to put 40 anything
in your car in January in Minnesota. 😮

Prepare to be boarded!

[The Boat House]

The thicker oil seems to increase the space between the
clutch plates. That’s my guess anyway. I checked the torque
to turn the prop when I changing the from gear oil to the
40W there was only an increase of about 10 lbs.

I don’t have an ARGI around here. The farm stores around
me don’t have a 40W except Tractor Supply but they only
sell it in 2 gallon jugs.

The number (Say 40) is the viscosity of
the oil. We needed to maintain it in some
of the coatings we ran using a Zhan cup.
I believe the weight of oil is (or was in the
beginning) measured the same the same
way. You time how long it would take for
the cup to empty. Using the same number
cup, 30W oil would take 30 seconds, 40W
oil will take 40 seconds, and so on. Multi
grade oils would be checked at different
temperatures.

A member sent me some of this.

[amuller]

quote Buccaneer:

I was thinking the “W” meant weight.
Either way, not a good idea to put 40 anything
in your car in January in Minnesota. 😮

I think the W is often taken that way, and oil is often sold as "40W."

But if you look at the specs W clearly means "winter grade." Thus 10W40, etc. I know I have never seen a real 40W oil, and it doesn’t appear in the tables of SAE oil specs I’ve looked at, such as https://wiki.anton-paar.com/en/sae-viscosity-grades.

So I incline to think that "40W" is just a marketing term meaning "fourty weight" and the oil we want for the Martins is just plain SAE40 single-viscosity oil, which should not be hard to get.

(Note that in aircraft engine oils, a W in front of the number means "ashless dispersant," not "winter" and has nothing to do with viscosity.)

Alan

[Author]

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