getting a few more ponies out of a 70 johnson

I've got a 1988 Johnson VRO 70, with the oil injection setup removed. I mix 50:1 in it in the tank rather than having to worry about the oil injection giving up on me out on the water and toasting my engine. I know there are tricks for getting more power out of some engines, like bigger carbs, etc. I can't find much info about getting more out of a 70 though. If anyone has any tips, tricks, etc please let me know.

I don't know any easy mods for the 70hp. It's tuned pretty close to the edge for a stock engine.
The Merc 3 cylinder is only around 20lbs heavier. It is available in a 90hp version. I like the way they run.
Couple of things on these 3 cylinder OMCs. The water "tell tale" on some of the earlier engines is piped low off the block. If the water pump gets weak, the water pressure can bleed off through the telltale and the block doesn't fill with water. You still SEE water so it looks OK. The top cylinder bakes from no water. This is fixed by plugging the water fitting and tapping into the top of the block like the later engines. That way water can't flow through the telltale unless the block is full. Look and see if your water telltale is piped from the top of the block or down near the bottom.
Also, ignition timing and carb synch is everything on these. It's the difference between an engine you love and one you hate.

Increase compression and get out the porting tools for that one.
It responds really nice to matching the ports to the old 75hp blocks.
Bottom end power goes away noticeably but you can more than make up for it from 4000 to 7000RPM.
Oh....and you have to find an old non limiter power pack as well.

Since it's a 88 it could be a 49 or 56 cube motor. 56 started in 86 and 49 eneded in 88 so they over lapped 2 years. 49 you could match to 75hp porting but the 56 is a different block, but you could match it to the sst60 porting. should make around 90hp then. Compression helps. Porting will lose bottom end but makes big power on top. add finger ports and gain llow,mid, and in some cases top end. But it does make them pull a lot harder through bottom and mid range. You could also make a sst60 style exhaust tuner for it too.