Is my Mercury converted from 7.5 to a 9.8?

[kykayak]

Hello all...new member, this is my first post.

I recently bought a 1969 Mercury 7.5 HP outboard. The powerhead had recently been replaced with a powerhead from a 9.8 HP 110 model from the early 70's. While the carb was rebuilt, it's the carb from the 7.5 thats on my motor. I'm wanting to get all the power I can from this 7.5.

In order to get all 10 HP, do I need to change the carb to one from the 110? Or is the powerhead swap already bringing out 10 HP without changing the carb?

Thanks all for any input!

 

[Laddies]

Re: Is my Mercury converted from 7.5 to a 9.8?

Back then the 7.5 and 9.8 used a different number powerhead but if yours has been replaced with a 9.8. Then carb don't have to be replaced as the only differance was some used a differant main jet, early carbs (tillison) for the two both used .040 main jet. How ever later carbs (walbro) the 7.5 used a .040 main jet and the 9.8 used a .039

 

[kykayak]

Re: Is my Mercury converted from 7.5 to a 9.8?

Back then the 7.5 and 9.8 used a different number powerhead but if yours has been replaced with a 9.8. Then carb don't have to be replaced as the only differance was some used a differant main jet, early carbs (tillison) for the two both used .040 main jet. How ever later carbs (walbro) the 7.5 used a .040 main jet and the 9.8 used a .039

Thanks for the quick reply. Sorry, I'm new to outboard mechanics. Yes, the powerhead is off a early 70's 9.8 motor. My current carb is the rebuilt Tillison from 1969. However, I purchased a Walbro carb from an early 70's model 9.8. So, would I see any benefits or gains by switching out the carb from the Tillison to the Wallbro? Or, will I have the same performance with my current Tillison? Thanks for any comments or suggestions.

 

[Laddies]

Re: Is my Mercury converted from 7.5 to a 9.8?

just check the main jet to see if it's a .039

 

[mercury713]

Re: Is my Mercury converted from 7.5 to a 9.8?

The throat of the carbs are same size? on my johnson expl 6hp to 8 hp the difference was thoat size was 1/8 differance. just a thought... maybe others are sure just jets differance

 

[bob1340]

Re: Is my Mercury converted from 7.5 to a 9.8?

From what I can see, on my 1970 model 7.5 the only difference between it and a 9.8 is the carb. I've cross referenced most all the parts and with the exception of the carb the parts are the same. Look at a parts chart.