Mercury 25hp Longshaft working like a 4hp :(

[jake3340]

I have a mercury 25hp just like this one http://smalloutboards.com/m2500.htm

but longshaft, last summer my engine over reved and I melted the piston nd broke it. My mechanic put me a new piston and rings, but for some reason the engine is working like a 4 horse power, and im not sure if something is wrong with the piston because im hearing a strange noise like something is knocking around in there, also i just released that I found a small bent metal rod in my room that had came off the engine, you can see a picture of this rod here...



What is that rod ? Is it important ? Could it be this is why my engine is not going up to full gas ?

 

[Shadow662]

Re: Mercury 25hp Longshaft working like a 4hp

I could be wrong and I'm sure someone will correct me but that rod looks to me like it controls the timing advance. As you push the throttle forward it will pull the timing advance and will not run right until the timing advance is correct. So if that controls the timing advance it will run like crap. Someone may correct me or agree with me but if you are in a rush you can start the engine and as you put the throttle forward move the timing advance forward. To see if it runs better. That rod you are showing that is bent/missing is part #42161 and costs around $2 so replace it then try.

 

[jake3340]

Re: Mercury 25hp Longshaft working like a 4hp

Thanks so thats probably the problem why its not going into full gas ? I have the part over here will go stick it on soon and see how it goes, thanks!

 

[jake3340]

Re: Mercury 25hp Longshaft working like a 4hp

Just checked, it was there not the problem, what could it be my engine isnt working at full capacity, moves like a 4hp. Could it be the mechanic didnt put on the piston properly ? Are there any manuals how to dismantle one of these and fix the pistons ?

 

[Shadow662]

Re: Mercury 25hp Longshaft working like a 4hp

First I would call the shop that repaired it and see what they have to say. If they won't fix it and you are set on doing it yourself you can buy a service manual for your engine which will guide you threw the procedure check online auction sites for the best price. I would buy one that is a Mercury manual specific for that motor not an aftermarket that covers a long range of motors.
In the service manual it will tell you what the compression on the cylinders should be then I would do a compression test and see if both cylinders are in range of spec. If the compression is in spec internaly you should be OK. Or if you don't want to spend the money on the service manual until you know you have to tear into it you could call a Mercury dealer and ask if they can tell you the compression specs for your motor. Compression testers aren't expensive and some chain auto parts stores you can rent them for purchase price and return it for a refund after you've finished.
It also wouldn't hurt to clean the carbs and see if that makes any diffrence. Also check to see if that timing advance moves forward when you push the throttle forward.

 

[jake3340]

Re: Mercury 25hp Longshaft working like a 4hp

Ye it moves forwards, when the engine is idling it revs up to full, but driving nothing, anyway thank you very much for your help, the place that repaired my engine don't know what they are doing and im sick of everyone telling me to wait so I get something fixed, I will try find an online manual for my engine maybe il get it fixed lol. Thanks again mate.