I have a 1988 25M Mariner. She has provided flawless (well almost) service for 19 years. Coming in from my last SCUBA trip she died. Just quit running. Thankfully we were in far enough to find shelter behind some rocks. Anyway it sounded like she was starving for gas. When I got home I started to check things out. Lots of spark and lots of fuel up to the carb. I even got it started when I used the choke and actuated the "primer pump". But it would only run for a few seconds. It still sounded like it was running really lean just before it died. I got the idea to cover up a portion of the carb throat. Sure enough, if I cover just the right amount of carb, I can get it to run at any throttle position (no load). So I think that I am just about to rebuild the carb. But before I do, I thought I would pick a few brains for ideas. There must be something in there blocking off the full flow of fuel, a jet or metering valve or something. I have never opened up the carb on an outboard, lots of Rochesters and Carters on cars (back in the day). Any thoughts from you people about this problem?
carb is a good place to start. you know carbs, so you know there could be crud in it, float stuck, etc. other options could be the fuel pump failing. the fuel hose could be collapsing inside, check valves in primer bulb could be bad.
does the primer bulb pump up hard? if you get it started and pump the bulb, does it perk up?if your tank vent was plugged, it should still start and idle but not rev very high and rectify itself when you take fuel cap off to check fuel. the fuel hose connectors and their mates on tank or motor could be worn, allowing a lot of air to suck in instead of fuel. but you should see a fuel leak when you pump the bulb. bad fuel lines on motor would give you same results
i have 1986 25hp marinern + workshop manuel. i can fax you exploded view, of components. im usless with the computer . you can e mail fax no to tommix45@yahoo.com 2 types of carb used one has marking w.m.c on flange (split bottom cowl) the other model has B.C. marking. (thumb srcew idling adjuster. the manuel covers ser.7207858and up for canada.6416713 for usa.
I haven't had the chance to tear into this ...YET! (I got weigh-laid in yard work) Tommix, I will get that serial number and get back to you,. Diaric, the squeeze bulb pumps up hard and the lines up to the quick connect on the motor seem to be just fine. The primer that I referred to is a small pump actuated by a lever attached to the choke mechanism. Manually pushing this allowed me to start the engine and then the hand over the carb throat let me run the engine. The information you gave me about the fuel line inside the cowling is right on the money. Another person I know rebuilt his carbs and then discovered that the real problem was a fuel line that collapsed when the engine was running. Very soon I will be able to spend some time under the cowling. Until then Thanks
I'm currently having a similar problem w/ my 1995 25hp merc...I have the service manual on CD if you need anything. Anyway I put 50:1 in a spray bottle and sprayed through carb and got it to fire so at least I know it's a fuel issue.
Unfortunately this will be my first carb rebuild.....so I'm not sure what to look for.
Mariner 25 HP carb problem
Re: Mariner 25 HP carb problem
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