TOPIC: Upgrading 1975 1500 to an XS??

First off, I'd like to say Hello! I'm new to the forum and up until this past February I have been New to the boating community.

Long story short, I have purchased a 1971 Checkmate MX-18 with a 1975 Mercury 1500. When I purchased this boat the motor was non-running. I did a compression check which i had 125-135psi and with some new wiring and a lot of cleaning I got it to fire! Actually got to run pretty good the last time out getting up to 45mph. But, upon trying to restore the paint and exterior I've came across more severe challenges. The sub-floor with the center stringer was rotten along with the transom. Which I will be replacing this coming spring.

But my question is, besides the shorter lower unit, can I turn this 1500 into a XS by just changing the carburetor jets and adjusting the timing or do I need to to oversize the pistons and do a complete overhaul? Also, from my understanding in 1975 Mercury didn't make a XS. It was actually an SS. Is that Correct? Also, does anyone know where to find the cowling vents to make the original cowling?

Thank You for your input as always it is Very much Appreciated!!

1500 XS was 1976-77. I believe its more than jets and timing, so I'll let the gurus chime in. The MX was pretty light in its day,a properly tuned 150 should nudge 60 stock. When rebuilding the transom add knee braces so the stress is distributed better, and leaves the option of adding a jackplate. Make sure you have an accurate tachometer when you make speed runs, will help greatly when choosing a propeller. Good luck, and keep us in the loop.

Thanks Kerry for the reply! Will definitely be adding the knee braces in! Ya, the tachometer I was using I don't think was accurate... Was an old Autometer Tach that I had lying around. The original one doesn't work. The prop is a 19 pitch aluminum. I will for sure keep everyone posted on my progress! I have the boat completely stripped down, rub rail off and rivets drilled out. Everything's ready to lift the the top off just started too late in the year and decided to cover her up tightly and wait till spring. But over the winter I want to try to refresh the 150. Just really don't want to have to pull pistons and all that. But, who knows? Maybe I will just pull the powerhead and have it rebuilt?

Thanks Again!

A real XS is a different engine, with raised ports, louvered cowl, special low water pickup in the gearcase, unique graphics and so forth. A nice little find if you can get one today.

Powerhead wise there is very little difference between a 1975 1500 and a 1976 1500xs.

Same carbs same block same everything. The blocks have very slight port timing differences. The difference would never be felt on a boat weighing more than 400 lbs.

Some racers actually preferred the standard block because it possibly had more "grunt" in the mid range RPMS.

The 15 inch mid, low water pick up lower unit, red stickers and a J stamp are all that makes a xs a xs. The louvered cowl was actually on non xs motors as well.

Conrad

Whoops, wrong place me here..as wrong thread..

Thanks for the detailed reply Conrad! I'm going to start tearing it down to clean it up and rebuild the carbs. And was wondering, other than having good compression, is there any other reason for going into the Power Head?

Thanks Again!