94 mercury 135 black max

[Jola454]

What can I do to get more power out off my 135

[wired247]

How much money do you have?

[wrechin2]

If the engine is still running.....For starters you can gain 15HP by changing the carbs as the 135 and 150 are the same engine. Then you can start with the basics.....Cutting the heads to raise the compression and increasing the timing slightly (after removing all the "black" boxes) on a healthy engine. There are many things that can be done to a 2L internally to spruce it up (especially the fat block 2L) but then it becomes a issue of the cost of the mods versus stepping up to cubic inches (2.5) as sometimes it is more cost effective and then Wired247 question becomes a very good one. Just my .02

[Jola454]

How much can I shave off my heads and still run 91 octane

[wired247]

Tightest you'll want to run is about 28 cc's chamber size. Idle relief slot motors cant really be tested for cranking compression like non slot motors and give you meaningful numbers . 28CC works fine on 91.

[V-bottom]

What can I do to get more power out off my 135

Not sure how much money you were looking to spend for the improvements. We had the same scenario back in '07 or '08 and figured rather than spend the money to "get more out of the 135" we sold the 135 and went for a used 2005 175 Opti ( 2 years old at the time) and picked up 10 mph and way better fuel mileage and all around performance. The 175 was only about 35 pounds heavier than the 135 so it was negligible. Good luck with your decision.

[wrechin2]

I always cut the heads to the same cc as if it was a non-idle relief engine because as mentioned you can't get a accurate reading on compression but will have the same increase. A lot of factors come into play but I would agree 28 would be safe. We have ran 26cc here but have better fuel. Just my .02

[Jola454]

Do you measure cc size with or without the spark plug hole filled

[wrechin2]

With the plug that you would run such as a NGK BU8H installed in it.

[Jola454]

Had them cut down to 30 cc should a guy polish up the combustion chambers as long as the heads are off