Cubic Inch

I Guys.Ihave a 90 hp 3Cly. Reb

I Guys.Ihave a 90 hp 3Cly. Rebulit Bored 20 over.All 3 Cyl. What Is Cubic inch And hp Its A 1987 s#0B174136 merc. Thanks in advance. Arcrat

"Robert, I will double check b

"Robert, I will double check because the 90 did go through one major model change, but believe it is based on Merc's 84.6 cubic inch powerhead (which it shared with the 70, 75, and 80 horse over the years).

Bored over will not make a significant difference to factory displacement since each over bore is only .020" from original. So for example, the bore went from 3.5000" to 3.5020"

The 1980-something, 90 horse Mercs put out close to 100 actual horses (97 to 99 on average) at the prop if tuned well.

Merc traditionally "under rated" their horsepower so they would look good compared to the competition. However, when the EPA got into things all mfg's tightened up their rating numbers.

Since the old 90 was putting out about 100 horses, plus the level of emissions for a 100 horse, it looked like a "very dirty" engine, so the practice ceased. Now most engines are within about 3-4% of advertised horsepower and it is illegal (at least in the US) to alter the horsepower from what is listed on the EPA sticker..."

"Ok, I was a little bored [img

"Ok, I was a little bored

If the motor was originally 84.60 cubic inches then boring out all three cylinders by .020" would change the displacement to 84.66...."

THANKS Graham Do you have any

THANKS Graham Do you have any info I should know about on the motor? spec bore 3.375 max pm 5500. arcrat from oklahoma....}} plus 0.20