Shaft length

[tacx]

I have a 1970 9.8 hp 110 Mercury outboard . Measuring from the ventilation (cavitation) plate to the top of the transom with the motor vertical it measures 17" ? I thought that standard shaft lengths were 15" , 20" , or 25" ? Is 17" an odd ball? My boat transom is only 15" ?

Thanks
Tom

 

[racerone]

You are mistaken in how to measure shaft length !-----Your motor is a short shaft meant for a 15" transom

 

[tacx]

Interesting? How does one measure ? Everything I read tells me I measured correctly?

to be more specific. I measured from the top of the transom clamp ( where the clamp sits on the top of the transom ) to the anti ventilation plate. I get 17" ? I don't care what you call it ,short, long, or extra long, it's still 17" .
Now my question for old merc owners. Is that a standard length for that motor?

Thanks

TOm

 

[racerone]

If your motor was a " long shaft " than the measurement you made would be 22 inches .----That would be for a 20 inch transom.------Go talk to a shop that knows your Mercury motors.

 

[flyingscott]

17-18" for a shortshaft motor is pretty standard measurement across all outboard manufacturers. My 1992 johnson 15 hp and 1985 evinrude 15 hp measure 18" for a shortshaft. My 1955 Scott -Atwater 10 hp measures 17" for the shortshaft. Your motor is nothing special as far as that measurement, just a shortshaft motor.

 

[tacx]

Thank you, flyingscott,

so, my boat has a 15" transom and with the motor sitting on the transom the anti vent plate is 2" below the bottom of the boat. I thought that the proper level for the anti vent plate should be even with the bottom? Do I need to build up the transom?

 

[flyingscott]

My guess is your boat does not have a lot of angle to the transom. You can put a block of wood under the motor to compensate. That is pretty common to happen especially on older boats.