I have just [yesterday] bought an old Mariner 3.5hp outboard (I believe this is actually a Yamaha?). It was started in a tank when I bought it and run off the choke in and out of gear, etc and seemed great so I paid the man his money. Put it on the back of the dinghy in the evening and it barely would run at all off the choke and either on or off would not rev above mid throttle in gear? I have read other related forum apends and have noted comments relating to jammed floats and dirt because the only other things that happened to it were being laid on its side in the boot and getting a full tank of 50:1 unleaded 94 petrol [2 days old]? it was also at a slight angle [trimmed in] from the transom ... any help would be great? ... SeaBear
I would still suspect the carb,Seabear.The fact that it ran fine before it was laidon it's side, means that something in the float bowl (a piece of debris,water,old fuel)got into the pick up tube,and is now "hanging-out" there.Remove the bowl,and see if there is anything in it.
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Thanks 12Footer ... I removed the carb and blew [mouth not airline] most of the jets, etc but there is a small brass tube which runs vertically from top to bottom of carb and passes through the throat of the carb? Not seen this before - but the tube didn't want to come out so I didn't force it? Anyway, rebuilt the carb and refitted it also emptied the pipes and tank and used fresh petrol/oil and restarted it - slightly better but still playing up. I guess I should do it again but remove this tube and check it out as it may have an orifice in the tube where it passes through the throat and it may be blocked? Does anyone know if this tube is just a push fit or what?
That brass tube is the pickup tube, and is a prime suspect. It acts like a the tube in one of those lawn sprayers.As water from the hose (air in the case of your carb) flows-over the top, it sucks fertilizer (fuel in the case of your carb) out of the canister (bowl on you carb).They do come out, but can sieze in-place.I have broken them before,so you are right in your caution. I would take it to a garage, and ask them to clean it with compressed air. This doesn't allways work,and in worse case,you WILL have to remove it.Also, note that there is a brass venturi on the side. This is the jet, and if plugged will cause the same thing. It meters the fuel.
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"Did you hear about the guy whose whole left side was cut off? He's all
right now."
Bingo! I completely stripped the carb and when I removed the little brass tube, etc they were covered in crud. In fact the tube/jet that is the feamle to the long brass tube has about 8 drillings - well 3 of them were completely blocked! Anyway I didn't finish until 7pm so I'm off up the river tomorrow to test it but it ran great in the dustbin!!! Thanks for your help ...
OK - I spoke too soon! It started up fine and would sit at a nice idle after about a minute and off the choke! So, after ithad run for a bout 5 minutes I cast off and up the river I went, against the tide so if I did have to row?? Well, it runs for about 15 minutes and then dies and will only restart if left alone for a bout 5-10 mins and then it ran for another 15 mins and died? I have put an inline filter in after cleaning after the carb but there is quite a lot o frust in the tank ... I'm pretty sure the tank breather is OK but does anyone have any other ideas?
I was just wondering if a fuel pump can be fitted to this outboard? Partly to improve fule flow in case the inline filter is restricting flow? Also, because I could also use a remote tank ...
Ahoy, SeaBear. Yes, a fuel pump can be fitted but it wouldn't be a "factory" job. I have seen (and done) adaptations of OMC small engine fuel pumps to engines not originally intended for remote tanks. It requires a little machine work to make a mounting plate for the pump, drill and tap the crankcase for a fitting to attach a small tube to provide crankcase pressure/vacuum to the pump, and finding an appropriate spot to actually mount the pump. I ran a Johnson 3 hp with one of these adaptations off a 6 gal tank for several years. Worked marvelously. BUT! if you can't do it yourself it could be very expensive, perhaps prohibitively so.Good luck.JB
Ahoy JB! Thanks for info on fuel pump ... do you know what the small rubber pipe is on the side of the crankcase on this engine? It is only 2 inches long and loops out of the crankcase and then goes back in an inch away? I had assumed this may have been for a pump but if not then what is it for?
Mariner 3.5hp choke problem
The fact that it ran fine before it was laid
Linear Mode
