New project Mercury 150

First post here on the forum. I'm new to outboard motors and have a few questions. I just bought a boat with a 150 on it and I'm trying to get a few suggestions on what to do first. I was told by previous owner that he replaced a few parts in distributor and was able to get it running again. But it wasn't running right. All I KNOW is what I can see,,, The motor turns over freely by hand and half the bolts that hold the flywheel on are broke off. So my plan is to extract the broken bolts. Find top dead center. Put Flywheel back on. Do a compression test. Then if compression is even in all cylinders, try to time it. Hope that I can get it running. I've had many boats in the past, but they have always had Big Block Chevy's in them. I've never worked on an outboard motor, so I'm kind of guessing on all this right now. Going to need help to get her running. Here's what I'm working with. Any comments on what to do are welcome. I'll try to get serial number and post it.

Thanks,
Steve

You don't need to mess with bolt right now, check the compression 1st!!! and then for spark. It should be 130psi or higher and check the internal wiring as these are known for decay

OK. I'll do that. I know how to check compression and for spark. As far as internal wiring, not sure what/where to check. Other than checking for crusty powder at connections and on the ends of all wires that I can see.

You'll find it extremely hard to get those broken bolts out. Fortunately, there are lots of those hubs available on eBay and elsewhere. Might have a couple myself if you need one.

Jeff

Thanks for the offer Jeff, appreciate that. I can't stand looking at broken bolts while I'm working on something. Unfortunately through the years I've had a lot of practice on extracting them... I didn't have access to a compression tester yesterday. So after the family left and the wife was sleeping, I got 'em out. Those broke off, red loctite covered suckers had no chance. A little heat and they were out.

Compression check showed all cylinders at 110 cold. Grounded spark plugs look like they were all firing. Going to try to get everything lined up and see if she will run.

See if you can get to run without spending a lot$$$ and retest compression. If the engine has been rebuilt with low domw piston the compression posted is ok, if its the original high domes it way to low and will suffer idle and hole shot problems.The 150's with high dome tested out at 140-150 psi new...

Got It


So happy...... Had to chase down a bad fuel supply and run out of a 5 gallon jug today. But got her running smooth after link & sync. Compression was a little better warm. All cylinders around 115 warmed up. But she runs and idles smooth. I think have to do water pump. Ran it on hose for just under a minute each time for a couple times. I don't know. Maybe I just didn't wait long enough, didn't want to hurt anything from overheating. Never saw any water coming out the hole on side of motor.

Short video from earlier today:

Re: Got It

Serial number is 3505174. So looks like it is a 1973 150hp.