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View Full Version : outboard motor help..long shot? haha



motosno963
07-30-2012, 11:24 PM
soo my buddy at work just asked me for help with his 1990 Merc 50hp outboard..he says when its not under load it runs like a champ but when you put it in the water it wants to bog down..he said hes changed the fuel lines and filter, and also cleaned the carb..i asked him if he did anything with the fuel pump and he said no..im thinking its the pump but i could be wrong..any ideas?

kaneboats
07-31-2012, 11:45 AM
Hmmmm. Plugs? Wires? Timing? All the above?

Stazi
07-31-2012, 11:47 AM
Sounds like a vacuum related issue, because under load you will get a whole lot more vacuum. So I'm guessing there's a leak somewhere in one of the vacuum lines connected to the carb.

parrothd
07-31-2012, 11:59 AM
First thing is to check the compression....

ga-lsv05
07-31-2012, 12:14 PM
First thing is to check the compression....

X2 first thing I would check on a 2 stroke

2005 mobius lsv 2900lbs ballast

jmb
07-31-2012, 10:27 PM
Vacuum? Didn't know we used vacuum

lewisb13
07-31-2012, 10:50 PM
I dont think there are vacuum lines on that motor. Im guessing its the main jet. The pilot jet controls fueling at idle and just off idle. The main jet controls fueling above idle. Ill bet any money its plugged.

parrothd
08-01-2012, 12:03 PM
I dont think there are vacuum lines on that motor. Im guessing its the main jet. The pilot jet controls fueling at idle and just off idle. The main jet controls fueling above idle. Ill bet any money its plugged.

And if it's plugged and he ran it, which he did, he probably seized or melted the piston.. You need to check the compression before anything else.. :)

kaneboats
08-01-2012, 12:36 PM
Also check all the fuel lines. On outboards they tend to put wicked bends in the lines to get through tight spaces and get on fittings in tight little crannies. As the lines age they soften. I had one once that would run great for 10 min. but when you went to pull a skier or something it would wind up and then die. An old soft fuel supply line had softened and was getting sucked closed during heavy acceleration. Just something else to keep in mind.

Going back to the basics, you need ignition, carburetion & compression to run. You know you have at least a little of all three or it wouldn't run at all. So, now you need to be sure you have proper compression -- try a leak down test. You also have to be sure you have consistent fuel supply. And you have to be sure the timing is advancing correctly through the rpm range. Good luck!