Convert 7.5 Hp To A 9.9 Hp

[1KINGROOKIE]

What will it take to convert a 1975 mercury 7.5 hp to a 9.9hp.

 

[green4themoney]

Re: Convert 7.5 Hp To A 9.9 Hp

ive seen this before... all they did was swap the carbs, i dont know how much of a difference it really made tho maybe a little bit faster, they are close enough in speed anyways why would you want too?

 

[corm]

Re: Convert 7.5 Hp To A 9.9 Hp

Hi,

Don't forget to put the std pich prop for the 9.8HP engine on too.

 

[Moody Blue]

Re: Convert 7.5 Hp To A 9.9 Hp

What will it take to convert a 1975 mercury 7.5 hp to a 9.9hp.

A 1975 Merc 9.9.

Wouldn't waste my time or money on a clumsy retrofit that most likely won't work. Spend the money on a true 9.9 and sell the 7.5.

 

[7920hpMercury]

Re: Convert 7.5 Hp To A 9.9 Hp

You would think you could easily convert a 7.5 1975 to a 9.8 since the displacement is the same.

However, 9.8 intake and exhaust ports are larger and at a different centerpoint than the 7.5. Not to mention the carbs are also different.

So, the easiest fix is to get a 9.8 powerhead off ebay and a 9.8 carb and replace the 7.5 powerhead and carb. The rest is the same except as mentioned above, you maybe need to change your prop depending on the load you are pushing.

 

[1KINGROOKIE]

Re: Convert 7.5 Hp To A 9.9 Hp

Thanks to all replys. I think I will try and find a 9.9hp

 

[gomofast]

Re: Convert 7.5 Hp To A 9.9 Hp

You would think you could easily convert a 7.5 1975 to a 9.8 since the displacement is the same.

However, 9.8 intake and exhaust ports are larger and at a different centerpoint than the 7.5. Not to mention the carbs are also different.

So, the easiest fix is to get a 9.8 powerhead off ebay and a 9.8 carb and replace the 7.5 powerhead and carb. The rest is the same except as mentioned above, you maybe need to change your prop depending on the load you are pushing.

Is this true for the '81 merc models as well?