Re: 1500 mercury,good ? or bad ?
Man! Did you pick a bad motor to have an experience with! I'm assuming it was a Twin as the 4-cylinder Classic Forty's are some of the best little motors Merc ever made.
Merc didn't make a 150hp inline in '81 so it's older than that. Check out this Model/Year guide and it'll tell you by Ser # range what year the motor is:
http://www.autorepairmanuals.biz/site/573683/page/599222
The 150 had the highest specific output of any of the 99 c.i. Inlines so naturally it's the highest-stressed. It'll definitely give that bass boat a good head of speed and on the right hull is well-capable of turning 50mph+.
Of course it goes without saying (I'll do it anyway!) that you're looking at an "older" motor and, regardless of brand, it's gonna need some checking-out.
You'd do well to take it for a test run; if it starts up readily, idles well, accelerates smartly and runs out like it should, it's probably OK.
Follow that up with a compression check with an accurate gage. If readings are more than 10 psi different between cylinders run away fast! She's got ring problems and/or scored cylinders. Ideally, compression readings will be within 5 psi of each other.
If you can find a shop with a leak-down tester, all the better as leak-down is an excellent indicator of piston/ring/cylinder condition.
Check the gear oil, if there's water you could have seal or driveshaft problems. If the motor's older than approx '76 it'll have a mild steel driveshaft which might have corrosion issues too.
Since this is on a bass boat, I'm figuring it hasn't seen lots of salt and that's a good thing. Old Salty Mercs are due for lotsa maintenance and don't hold up as well as the old JohnRudes did.
Anyway, hope this helps and maybe you'll be an Inline Owner soon!.........ed
