Merc 9.8 hp upgrade?

sstatz

Recruit
Joined
Mar 31, 2005
Messages
1
Hi,<br />I was told that the same motor was used for the Merc 9.8 hp, as with the 15hp & that it was merely either re-jetting the carb/or that there was an actual kit out there to increase a 9.8hp to a 15hp.<br /><br />Is this true, if so, would a dealer be the best avenue for the parts?<br /><br />Thank you
 

JB

Honorary Moderator Emeritus
Joined
Mar 25, 2001
Messages
45,907
Re: Merc 9.8 hp upgrade?

Howdy, sstats.<br /><br />Welcome to iboats. :) <br /><br />There are many myths about changing jets to get a 50%+ increase in HP. They are just that: myths. They exist about almost every make. Installing larger jets can only produce a terrible running engine unless a LOT of other changes are also made.<br /><br />There are a few case in which changing the carburetor, or the carb and a few other parts, reproduces a higher rated engine with the same displacement, but the results never justify the cost.<br /><br />Sorry. :(
 

Barnacle_Bill

Admiral
Joined
Feb 8, 2004
Messages
6,469
Re: Merc 9.8 hp upgrade?

Not sure about your Merc but I have a Johnson 9.9 that would cost about $800 to upgrade. Its not worth it.
 

Dhadley

Supreme Mariner
Joined
Feb 4, 2001
Messages
16,978
Re: Merc 9.8 hp upgrade?

In the march 05 issue of Bass & Walleye Boats magazine they just did a 1999 9.9 Merc conversion. The total cost, including Boyesen reeds, was 272.90. They had some pretty impressive results considering it's on a blow up boat.<br /><br />Obviously it was all in the breathing. The difference between the two carbs was amazing. In the pic the 15 carb throat looks about twice the size of the 9.9. And the 9.9 had no tuner so that helped a bunch.<br /><br />In the end they still couldnt swing the next size bigger prop but they did gain performance overall. What was interesting was how much fuel was being used considering the hp. As a 9.9 it used 1.96 gal/hr which, as a rule of thumb, is almost enough fuel for a 20 hp motor. As a 15 it burned 2.33 gal/hr.<br /><br />Very interesting article.
 

Chinewalker

Fleet Admiral
Joined
Aug 19, 2001
Messages
8,902
Re: Merc 9.8 hp upgrade?

The model 110, 9.8hp shares virtually NOTHING with the 9.9 and 15hp models and cannot be upgraded. The 9.8hp is an "old school" 11-cube powerhead that it shares with the 7.5hp model. It was built in various incarnations from about 1940 to the mid 1980s...<br /><br />- Scott
 
Top