TOPIC: ~1990 Merc 40 hp Steal - Need help how to proceed

As a religious Craigslist watcher, I am trying to find an older 30-50hp motor to pair up with a classic 65 Lone Star I found yesterday.

I saw an ad for a 40hp Merc for $100.00. Said that he bought boat and owner said motor was bad but had good lower unit and working power T&T. Picture was grainy but looked like a newer Merc.

Called him and he said the guy said that the oil injection had failed and ruined the motor. Said he'd take $50 for the motor and wanted $50 for the controls and harness.

So into the bowels of the inner city I flew in driving rain.

Saw it laying in the mud on it's side and I immediately knew it was newer and looked great. We stood it up and rested it on a fence.
In the pouring rain I didn't want to even suggest hooking up the battery I had to try and turn it over and check compression for fear that he would realize it was not dead. So I put in in gear and turned the prop with my foot and you be the flywheel turned so I paid him a C note and ran as fast as I could.

Sorry for the long story and I am getting to my questions....

Wrangled it onto the transom of my new Lone Star alone and stared looking at it. Pulled plugs and wrapped a cord around the flywheel and it turned but pretty stiff. Tilted it up and squirted liberal amounts of pre-mix and 50% Marvel Mystery oil. Pull a couple times, squirt, over and over and it gets easier. Hooked up battery and controls/harness and it cranked easy spitting out the plug holes so I know know it is not too serious.

Stopped there and now I need to know how best to proceed.

Before I get to checking compression....a couple of things I saw with flashlight as it was now dark.

1) Looks like where the fuel line connector comes into the motor it goes to a T and one side seems to be missing a hose on the other side(though it does go directly on the other hose to the fuel pump.
2)found a 6 inch piece of small hard hose(unlike fuel line) laying inside the motor....gotta figure that out in light
3)Oil injection line looks to be hooked up fine.

Now how to proceed. When I test for compression...should I leave plugs in the wires and ground to block to avoid blowing electronics/power pack?(as I have read many times before) Would it be too late as I did crank it already with starter for a sec?

There is also a weird host in the leg hanging there(kinda looks like a speedo cable with a plastic fitting ....again check tomorrow and post pics.

Needless to say I am pretty excited about this find and even if there is a major issue with the power head it will still be a good investment I am sure.

Thanks,
Tim

Pull the bypass covers ( if equipped with them )and inspect as much as you can,

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Pistons and rings for sure.

careful it may be an oil injected motor that had a problem since it is so stiff or the block may have allowed water intrusion. If so rebuild what you have or find a replacement power head. Do you know the year? For $100 you are still ahead of the game. A clean good running in order 40 from mid to late 80's all serviced and ready is still a 1400 dollar motor used.

Pull off the head and tear into to see what ya got.

Though the serial number is a bit hard to read, I believe that the motor is a 1995(will continue that investigation). From what I heard and see(the crappy vinyl oil lines are laying in the motor broken) so apparently it starved of oil and bad things have happened inside the head. I will provide some pics in a bit.

The motor turns over both by hand with a rope and with the starter. It is pretty stiff though but no sounds or feel of metal etc.

I will surely have to pull the head off of it to investigate further.

Another question I have.... I have a 77 Merc 50(blue stripe) with supposedly good power head(I see new starter and coil etc) and was running a few weeks ago until lower went(drive shaft was a bit bent I guess).

Will the foot of the 1995 or whatever 40 fit on the '77 50hp? Crap...I think that the old 50 is a shorty and the newer 40 is long(and drive shaft on shorty is bad/bent.

And just dreaming out loud..... any chance in a blue moon that the power head of the '77 50hp would fit into the newer 40? That would certainly make the better looking engine for sure.

One last question(for now)... I need controls and harness for the '77 50. Am I correct in thinking that the blue stripe controls were the same in any of the 35-70hp range(like I believe the lower units were)?

Thanks for the help with this.

Tim

Update:

I got the correct serial number ( 0C267810 ) which I now believe makes it a 1990 Mercury 40 Classic.

Here are some pictures of the motor:







Here are the broken pieces of oil line I found in the head:



And the fitting with the tie and a piece of the line still on it:

you will have to pull the head to see if the 50 will mate to the mid section. It may very well because the blocks appear to be the same. I worked on one of these and disabled the oil injection. Still running strong.
The oil lines are cheapo's over time the oil gets tanic and breaks down the lines. Most people just do not pay attention to them and then OOPS!

Thanks Jim,

I guess that a good place to start might be to compare the powerhead gaskets ...if they line up then it will be a good start right? And without the SN for the old 50 ... It looks like they might be the same.

need to check other mounting items also.

Ok I took the easy route. Even though the power head was basically the same, with it having so many differences on the periferrals it would have been a tough retrofit.

After I tested the 77 500 and found compression excellent and it fired right up nice, I decided to take the foot off the 40 and it bolted right on. Running, shifting and pumping great so that will be the motor for the Lone Star. Just need a full set of controls and a little paint(she's a little rough looking).

I started tearing down the 40 and will hopefully have the powerhead re-bored and with new pistons should be a fine motor again. Of course I need to find a lower unit for it too now.

Picture showing the scored pistons/rings thru the inspection ports.