40 hp. mercury issues

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canadian omc

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Mar 31, 2012
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Location
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1980 mercury 40 hp. carburetor re-built by a local marine mechanic complete with a tune up ,now it hesitates when coming from idle up to WOT and at that it seems to labor and almost seems as though the timing is off! I would appreciate any and all advice,thank you in advance!!! BTW can anyone please tel me how to set the timing on one of these motors? thanks again.
 
I would advise that you get a mercury manual for your specific year and model. DO NOT buy a clymer or seloc manual, get the OEM service/repair manual. I doubt anyone will be able to explain how to time your motor on here, a manual will be needed. You may just need a link & sinc done because timing rarely gets thrown off.
 
i bought the boat and motor recently and the shop where the work was done will not honor any warranty as they dealt with the original owner. I`m going to a different shop today or tomorrow with it. Thank you all for your advice , and may i ask if any one has an idea as to where i can purchase a manual for this motor thanks again guys
 
Try ebay, you need to know the serial number of your motor and try to match it to an OEM manual. I am not good with merc serial numbers. Here is a link to some on Ebay

https://www.ebay.com/sch/i.html?_sacat=0&_kw=40hp+mercury+service+manual

You do not want a manual that covers 20 different years, you want the original OEM service manual for your motor
 
Johny25 said:
Try ebay, you need to know the serial number of your motor and try to match it to an OEM manual. I am not good with merc serial numbers. Here is a link to some on Ebay

https://www.ebay.com/sch/i.html?_sacat=0&_kw=40hp+mercury+service+manual

You do not want a manual that covers 20 different years, you want the original OEM service manual for your motor

I couldn't agree more but at the same time, what you want and what you can get is often 2 different stories. I've been watching ebay for a factory manual on my 20 horse merc for almost a year now and haven't seen one show up yet. I settled for a sealoc for now which at least let me get a proper tuneup on it. But I still haven't given up on locating a factory manual.
 
so i took the motor back to original shop to get checked out , well after $200.00 and 3 days i get it back and it still hesitates and sounds as though the timing is out! I was told by the mechanic that these old mercurys always run like that. So my question is do these motors always run rough or do you think my local marine mechanic is just playing me ? Thanks again guys for any and all help
 
Maybe one cylinder is dead. Like a bad plug. I have a 9.9 force and it acted the same way cleaned the carb and put new plugs in it and ran great. What I would do is start it up and run it then pull the plugs and see if one of them is wet. If it is change the plug and try it again.

Steve
 
canadian omc said:
so i took the motor back to original shop to get checked out , well after $200.00 and 3 days i get it back and it still hesitates and sounds as though the timing is out! I was told by the mechanic that these old mercurys always run like that. So my question is do these motors always run rough or do you think my local marine mechanic is just playing me ? Thanks again guys for any and all help



They do not run rough - that is some BS you are being told. Who would have ever purchased the motor new if it ran like crap


Does it backfire? Hard to start?

I doubt it is timing, w
start by installing new plugs then new wires, etc. Make sure you have fresh gas as well - it is gonna be a process of elimination
 
so i changed the plugs and wires now this thing runs like a champ , as it turns out one of the plugs was cracked on the porcelain. so again all i can say is thank you for all the advice and support
 
Wow,that was an expensive set of wires and plugs.
I think I'd go see the mechanic and give him the old set of plugs...
If they wouldn't give me atleast abit of money back,tell him thanks for nothing.
 
I know it's sort of late, but did the shop take the boat out for a test run after the initial repair?

Motors sound good when car or boat sits still, but really needs to be run under load.

I once had a car motor rebuilt. When I picked the car up, the motor sounded great but it wouldn't go faster than 45mph on the freeway! I gave the shop two chances to fix it but they kept insisting that nothing was wrong, so I took it to the dealer and paid them a fee to tear it down to see what was wrong. The crankshaft had the wrong size bearings on it. I got my money back via small claims court.

Glad you were able to resolve the problem with minimal expense.
 
took it out for a run today and it still seemed to run sluggish , then I remembered another post about hydrofoils causing drag removed them and now it runs smooth and planes better. I just can't thank everyone at TIN BOATS enough BTW how do you use the smilies? LOL I still haven't figured these out thanks again guys
 
I second that^^^ Hydrofoils when not installed at the proper height are worthless. The hydrofoil should not be in the water when the boat is on plane. If it is still in the water when the boat is up and on plane then it is doing more harm than good. Trim tabs are a far better investment if you need better planing at lower speeds.
 

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