TOPIC: 1990 Merc Classic 40 - In Deep Now What?

I picked up a 1990 Merc 40 Classic for $100 with controls that apparently the oil injection failed(line from reservoir broke and starved engine). I have quite a bit of experience for many years working on outboards but have never gotten as far as inside the powerhead but I thought what the heck lets learn and tear it down cause I could see the pistons were scored and Timmy Calmes said it might be saved it walls were ok.

I have it torn down and the powerhead broke apart and I am seeing some issues right off the bat.

First of all because it is oil injected there is a a screw gear that drives the oil pump off the crank or cam or whatever. Check out this picture of where the gear for the pump meshes with a gear running off the cam shaft. Looks like something is all melted in there.(right side of pic)



Now in that picture above check out the heads of the two bolts that hold down the piston connecting arms....see the wear and metal shavings? Now check out this picture of the other side of the block and gouges they made into it.



Ok now my questions...and no I don't have a specific repair manual for this year/model so be patient with me please.

From what you see what are your first impressions on the damage and what happened?

What are my next steps to remove the crank and get the pistons out to evaluate further?

Do I have to loosen/remove all of those bolts attaching the connecting arms or whatever they are called to the cam? What kind/size of torx socket do I need for that?

Thats enough for now and thanks for any assistance I get.

Have a great weekend.

Tim

Welcome to the world of " automatic oil injection ".

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Without maintenance these systems fail !!

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It appears that the big end bearing failed and the loose rod rubbed on the crankcase.

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So it looks like major repairs / search for parts is about to commence.

Ok... forget the questions about pulling the crank and pistons...I figured it out. It came apart easy.

Now have a look. Three of the 4 pistons are severely scored and the piston walls are also. The rings are all ok etc so what would cause this scoring? No oil lubricant by chance?

I think I have come to the decision that I am not into putting a ton of effort and hundreds of bucks into this thing and my best bet is to part out all the good stuff left after this bad situation.

Everyone agree?

Tim, the scoring on the pistons is due to the pistons growing from heat, due to the lack of oil. Given the condition of the oil pump drive screw there is likely particulate from that in the crank journal bearings and scoring there too.

Thanks Dave for the info. Too bad a good motor had to succumb to this fate by a simple problem like a cracked/broken line serving the oil. Just bad design to make like easier for users...like measuring and adding oil to fuel is so hard right?

see if you can find a good used power head. and put it back in service.is that an option?

I concur with Dave - the 44-cuber Mercs are great runners and well worth at least finding a donor powerhead to return that one to service. They made those 44 cubers for about 30 years, so finding parts shouldn't be an issue...

dont use the oil injection just mix 50-1

I believe that I have learned that lesson well by looking at the inside of this poor girl