18 repowering ideas

[bigblockdock]

I have a 1985 seacraft SF18 with a 87 115 merc and a 25" orig tansom. Turning a 17 inch pitch prop, top speed is around 38. cruise is around 27/28 mph. the motor wgt. is 316 lbs. The 115 is in excellant cond. but I want to repower to gain some mph. I've looked at the four strokers also and found them to be alot heavier and slower than the 2 strokers. I think a 140 sukie is in the 500 lb.which could be a bit on the heavy side for an 18 which was rated for a 150 before 4 strokers were around, but as someone said you can plug your drains and be ok. I'm presently looking at a 150 merc 2 stroke which weighs in at 415 lbs. Turning a 19 inch pitch prop the speed should be near 48 or 49 mph I think. Anybody running a 150 merc on an 18SF with some numbers? and can you raise the motor some on the transom? Butch