Mercury 2.5hp 4-stroke outboard advice

dartmoor said:
That's shocking - oh, and who says 4 strokes are more reliable than the two strokes they replaced! Really that is a terrible failure by the manufacturer if true....
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Yes, not good at all, in my case it was replaced under guarantee, however, the fact that the failure is not sudden, it can be difficult to diagnose and can mess you about when the engine stops one mile out in the sea
 
OK, so a friend of mine suggested removing the spark plug and putting half a teaspoon on fuel in the cylinder, which I've done and the engine does momentarily fire up but cuts out almost immediately. Before doing this I replaced the fuel and drained the reservoir in the carb.

I'm assuming this confirms that the engine itself is okay but there is still an issue with fuel getting through. The carb looks clean, I've removed the jet and cleaned it out. Is there anything else in the carb that I can check or between the carb and the cylinder? Or is there a way I can check fuel is getting through the carb?
 
vseager said:
Is there anything else in the carb that I can check or between the carb and the cylinder? Or is there a way I can check fuel is getting through the carb?
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If the carb drain screw is accessible check to see if the carb is filling with petrol. If not take the fuel hose off it and check that fuel flows when the tap is opened.
 
vseager said:
Okay I'll check that second jet, do you know which part I should be looking at on the diagram at this link...
http://www.boats.net/parts/search/M...OKE) Carb/0R131842 & Up/Carburetor/parts.html

I havent noticed any fuel on the spark plug. How do I flood the carb?
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My engine is identical to yours, only the size of the jets are different to increase power from 2.5 to 3.5. I had the carburetor out, yesterday, to unblock the jets because I could not start it and was running very rough when finally started. Looking at your diagram, i unblocked No 4 and no 18, I pulled out a single thread of copper wire from an electrical cable and used it to clean the jet holes. If you can see petrol coming out from the carb drain plug, when is unscrewed, then you can assume that the carb is full of fuel, if you can see fuel coming out from No 18 Rubber hose, then definately the carb has been flooded. When all is back together, try starting the engine with the choke out, then if it does not start, take the plug out and there should be fuel on the plug. if there is no fuel, there must be a problem between carb and engine. Try spraying "easy start" or petrol directly in the intake, If there is fuel but it does not start, then check for a healthy spark on the plug; if the spark is weak, its not good because the spark will not be able to jump across when under pressure inside the cylinder; could be faulty spark plug or likely to be the electronic ignition (~£60). The whole thing does not take more than one hour to do, however, can be very frustrating until you find the fault.
 
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Thank you all for your help, I tried most of your suggestions with no luck. I ended up dropping the outboard down to Bill at Home Marine on Saturday morning. He seemed to think that one of his services would get it running and he offers a 3 month warranty with every full service. As I have no idea about these small engines and have tried most options within my capability / comfort zone, I thought I would just get a professional to look at it.

Bill seemed like a nice chap who knows what he's talking about, and with a 2 week backlog of outboards to service people clearly like to use him, so hopefully he will get my motor running! :)
 
vseager said:
Thank you all for your help, I tried most of your suggestions with no luck. I ended up dropping the outboard down to Bill at Home Marine on Saturday morning. He seemed to think that one of his services would get it running and he offers a 3 month warranty with every full service. As I have no idea about these small engines and have tried most options within my capability / comfort zone, I thought I would just get a professional to look at it.

Bill seemed like a nice chap who knows what he's talking about, and with a 2 week backlog of outboards to service people clearly like to use him, so hopefully he will get my motor running! :)
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It a shame stuff doesn't just work. I fear that all the efforts to make these small engines comply with emissions regs means that they are vulnerable to carb faults - seems likes quite a few posts recently on small four strokes playing up after the winter.
 
catlotion said:
Did you make this change? I have a Mariner 2.5 and I've always felt it wanted to go faster but sounded governed. I read that they're basically the same engine as the 3.5. Is it just the jets that need changing?
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To my understanding, it is the same engine but fitted with different carb. I had to pay £50 extra for the 3.5 hp. The above post included a web sitehttp://www.boats.net/parts/search/Me...tor/parts.html which shows the jets for 2.5 and 3.5 hp. Perhaps that is all it needs to increase the power; a 3.5 hp engine will get my inflatable on a plane, a 2.5 hp will not.
 
vseager said:
Thank you all for your help, I tried most of your suggestions with no luck. I ended up dropping the outboard down to Bill at Home Marine on Saturday morning. He seemed to think that one of his services would get it running and he offers a 3 month warranty with every full service. As I have no idea about these small engines and have tried most options within my capability / comfort zone, I thought I would just get a professional to look at it.

Bill seemed like a nice chap who knows what he's talking about, and with a 2 week backlog of outboards to service people clearly like to use him, so hopefully he will get my motor running! :)
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Will you please let us know what was wrong with your engine, it is good to learn.
 
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