Low RPMs, WOT, 1994 Mariner 125

[JPJG64]

I have a 1994 Mariner 125, 2 stroke, 4 cyl, that won't get over 2300 rpm at wot. The engine seems to run smoothly, just no power. It runs up fine when run out of water with muffs. <br />I think the fuel had been in the tank for a while. I have drained and refilled tank with fresh fuel, checked compression (Within tolerance all cyls). Replaced sparkplugs, have good spark on all cyls. Checked ignition system according to Mercury Manual. Everything appears to be within tolarances.<br />I am in the process of disassembling and cleaning<br />carbs and replacing fuel filters. (I cannot find a filter on the boat Alumacraft 185 Phantom). Can anyone give any suggestions on what else to check while it is disassembled? Any help would be appreciated. Joe

 

[jim dozier]

Re: Low RPMs, WOT, 1994 Mariner 125

Your are not running on all cylinders. If in fact you are correct that you have spark on all cylinders and the compression is good, one of the cylinders isn't getting the proper mixture, too lean or too rich (probably too lean). It would have been nice to know which one but you will probably fix it when you've rebuilt the carbs. Do a complete job and dismantle them and pay particular attention to both the high speed jets and idle jets and float valves. Remove non-metallic parts and soak in carb cleaner overnite, blow out with compressed air and install a rebuild kit.