Mercury 9.9 Mod

[geary]

I have a friend that has a 9.9 Mercury ( Don’t know the year). He wanted to know if it can be changed to a 15hp by changing the carburetor ? I know it can be done on a Johnson or Evinrude 9.9hp just not sure if it can be done on  Mercury ? Any suggestions or help would be appreciated. Thanks

 

[RICHARD A. WHITE]

You could try to look up the parts list of the 2 motors and compare parts…

http://www.richardsoutboardtools.com
classicomctools@gmail.com

[Michael Anfossi]

Yes it can be done, have done it several times

[Gary Kosiba]

Hello group, I recently picked up a 9.9 Merc and would like to try this Hp modification.  Would it be just a carb swap or is there any modification to the intake or exhaust as well?  Thanks

[seakaye12]

It would be a whole lot better if we knew the model of the motor you are working with.  2-Stroke?  4-Stroke?

9.9 points to a newer Mercury series;  the ones they sold through the 60’s 70’s and 80’s was technically a 9.8.

With Mercury it is always best to work with the serial number.

[Gary Kosiba]

I have the info now.  It is a 110 and the serial number is 4840180.  Thanks in advance for your help.

Gary

1 user thanked author for this post.

Tubs

[seakaye12]

OK Gary,  your serial number shows a 1978 model which was the long running 10.9 cubic inch block which began in 1962 and went into the 80’s.

Mercury did not offer a 15HP version;  they went from the 10.9ci  9.8HP to a 21.9 cubic inch 20HP block.

At a paltry 10.9ci….I doubt that much more performance can be squeazed out of your 9.8.  It is already a tuned version of the 7.5HP motors.

1 user thanked author for this post.

Tubs

[Gary Kosiba]

Thank you seakaye12 for the info.  I appreciate you taking the time.  Gary

[outbdnut2]

Note that the 9.9 replaced that 9.8 in 1986.

Dave

[Author]

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