What gearcases interchange with 300X?

**simpson_3** · 12-06-2021, 11:41 PM

Would a sportmaster off a 2.5 promax fit on a 300x? I was under the impression that it wouldn't but I've heard of people running a 2.5 case on their 300x.

**outboards4life** · 12-07-2021, 09:41 PM

negative. need a 3.0 liter case

**David - WI** · 12-07-2021, 09:45 PM

But there are 2.5L and 3L Sportmasters.

**25two.stroke** · 12-08-2021, 01:59 AM

Depends on the mid. If factory then everything above is correct. If someone was building a 300x 15" then its possible they made adaptor plate to mount the 300x on a 15" 2.5 mid and then ran the 2.5 lower with a 13 spline driveshaft. I dont know if you wanted to get that deep into it, but its possible to do, but not practical to do.

For a stock 20" 300x the 3.0L sportmasters (250xs, 300xs, 300x etc.) will all fit. So will the 250 proXS torquemasters and standard fishing lowers.