Mariner 8hp 2 stroke what year is it serial number 9516681 Hi ive recently purchased this engine and i am having trouble finding the year of the model.. engine idles fine and revs up with no problems but as soon as i select a gear it wont go over 1500 rpm under load. seems like its starving of fuel.. tank vent is open and carb recently been cleaned.... please help

SOURCE: Mariner 25 hp 2 stroke hard to start then quits and won't restart

It sounds like the float is sticking in the carb. Since the carb is higher than the fuel tank it pulls the fuel in by vaccum of the engine. when running at high rpms, it can burn the fuel thats flowing into the carb, when you idle down, the bowl of the carb is filling up with fuel faster than the engine can burn it and causing it to flood. Then when it shuts off at idle it does not want to start back up because it is flooded. To make a long stary short, pull the carb and give it a good cleaning and your problems should be solved.

SOURCE: 2003 115 mercury efi losing power

I am a Mercury certified technician. What you need to do is take it to a Mercury dealer and have them hook it up to the computer. It sounds like the engine could be in Guardian mode or possibly a high RPM misfire. It is not something that is common and the computer program that Mercury has for those is able to test misfires and all sorts of cool stuff. It can also tell you if the engine was broke in properly, how many actual running hours are on it and even at what RPM each hour was ran. It will be able to bring up all faults that it has had in the past and any faults that are current. I know that you are probably looking for a quick, easy fix but for this problem I dont think that there is any way around taking the engine in. For what it is worth, if they charge you for more than 2 hours to run it on the computer then take it somewhere else. I can fully test the engine with the computer in about an hour. The only reason that it would take any longer is if they had to put it in the water to duplicate the problem but most shops will have a test tank that is capable of running your engine under a load at full throttle. Sorry for the bad news but I cant think of any other way and throwing new parts at it is just going to get expensive quick.