40 hp Mercury to much compression

[cyrusperry]

hello everyone I'm having some problems with this old motor, when I turn the key with the spark plugs in it seems to be having a hard time turning the fly wheel but if i take out the spark plugs the thing will spin away no problem. it like their is too much compression. also im haveing a heck of a time finding out the year the ser # 7197937 model # 1040222 can anyone give me the year thanks.

 

[3car]

Re: 40 hp Mercury to much compression

too much compression, or a weak starter? my guess is the latter. check all your connections, then grab a compression gauge and see what tale it tells.

 

[cyrusperry]

Re: 40 hp Mercury to much compression

even when I pull the pull cord I can hardly pull it with the plugs in.

 

[aquia creek slayer]

Re: 40 hp Mercury to much compression

i would have to say that you have a weak starter as well i own a mercury 40 as well and have had some starting problems in the past . when was the last time the starter was rebuilt a brush kit didnt cost but a few dollars for mine and made a world of difference . you might want to start there . fyi my compression is 170 in bithe cylinders... hope this helps.

hello everyone I'm having some problems with this old motor, when I turn the key with the spark plugs in it seems to be having a hard time turning the fly wheel but if i take out the spark plugs the thing will spin away no problem. it like their is too much compression. also im haveing a heck of a time finding out the year the ser # 7197937 model # 1040222 can anyone give me the year thanks.

 

[cyrusperry]

Re: 40 hp Mercury to much compression

just got done doing a compression test and it was 125 top cyl and 135 bottom cyl so is this good, bad or just ugly. also can anyone tell me the year the ser # 7197937 model # 1040222

 

[diaric]

Re: 40 hp Mercury to much compression

that compression, looks good. i don't see your serial on any lists.that number would fall into about 1982 canadian made, but as i said i didn't see it on any of the list i looked at. when you did compression check, starter turned it over really good?

 

[cyrusperry]

Re: 40 hp Mercury to much compression

no it was still slugish when it was turning.

 

[diaric]

Re: 40 hp Mercury to much compression

how does it run? does it run smooth or like somethings binding? if it runs and idles good, then the starter would be the most likely problem

 

[cyrusperry]

Re: 40 hp Mercury to much compression

i just got the thing a week ago and when I put new plugs into it this is the problem I ran into so even after i get this problem sorted out I dont no if it will start and run; the guy I got it off of said he had it running but you know how thing go when buy second hand ( you roll the dice you take your chances) so Im going to take the starter off and make sure everything is good with it. Im keeping my fingers crossed that the starter is week.

 

[andy6374]

Re: 40 hp Mercury to much compression

Have you checked your battery??? and the connections??

 

[cyrusperry]

Re: 40 hp Mercury to much compression

im going to trace it all the way fron the batt to the starter befor i start ripping it apart.

 

[jimc_LA]

Re: 40 hp Mercury to much compression

cyrusperry,

This may sound crazy, but something you mentioned in your last post made me think of it. You indicated that the problem may have started as a result of you changing the plugs. Are you sure that you've got the right plugs? If they are a slight bit too long, they might be making slight contact with a piston head, making it seem like it is hard to get beyond that point (like too much compression).

Chances are that it's the starter like others suggested, but on the outside chance that it's something like this, better to find out now than after it cranks!

Was it spinning over fine prior to you changing the plugs?

jim c

 

[wildthingn]

Re: 40 hp Mercury to much compression

pull your lower unit, i had same problem, posted question all over got different answers none work, found out the hard way buy removing engine, turned over fine with plugs in, do your self a favor remove lower unit, first drain lower unit lube, mine was real low, put in a cleaner and flushed and new lube turned it over with a socket alot, losened it up works fine,,, hope this helps a lot of extra work.....

 

[sailorden]

Re: 40 hp Mercury to much compression

Hi

I have the same problem, its turns like a dead dog with the plugs in, but when you take them out it spins like a top!

What did you do to solve your issue?

Please let me know as my wife is about to take a new lover because I'm spending far to much time in my workshop filling cylinders with oil and turning by hand to encourage it to behave like a normal old Mercury!

Thanks
Sailorden

 

[Starcraftguy1]

Re: 40 hp Mercury to much compression

I have a 1995 Mercury 40hp pro series,To tell you the truth I do think that you have the wrong plugs.You don't know the year,so,how can you have the right plugs.First find out your year of motor,get the right plugs and try it.A lot cheaper then dropping the lower unit and rebuilding a starter.I live in Arizona and take my boat out every weekend.I would start there,and while you are at it,replace your fuel filter.Hope it works for you.