Merc 40 help for outboard newbie

MercN00b

Recruit
Joined
Dec 26, 2002
Messages
3
Folks, <br /><br />I've been lurking here for a while and have to say this forum is very helpful. I've run some searches, but can't seem to come up with my exact problem, so here goes:<br /><br />I have a 40hp Mercury outboard, 4 cylinder, 2 carbs, 2 stroke, model ME40-ELPTO.<br /><br />Motor will run all day on the hose, or on the water at less than 2/3 throttle. At around 2/3 throttle, the engine surges badly. Above 2/3 throttle, the engine runs fast and smooth, but shortly dies like someone just shut it off.<br /><br />When the engine dies, restarting is difficult. I pulled a plug right after the engine died, and it was dark and very tacky/sticky and dry. Usually the plugs are wet and oily. That confused me because i swear i could smell fuel as i was cranking.<br /><br />Also, the primer bulb was a bit soft, but not collapsed when this happened. I ran the motor for about 20 miles today at 1/2 throttle, and it runs smooth, but go full throttle and you have about 5 mins till a quick stall.<br /><br />Also, the idle could be better, it seems a bit rough and weak. It seems to start fairly well, but starts easier warm when the idle speed is set high and a tap of choke is given.<br /><br />So far, here's what's been done:<br /><br />Cleaned old plugs<br />Decarbonized motor (I followed directions on ValvTect can, and piston tops have carbon, but no visible carbon on the pavement after decarbing, what did i do wrong?)<br />Installed fresh plugs<br />Old oil looked like death, so dumped it<br />Filled oil reservoir with Penzoil Synth TCW3<br />Added some decarb (looks like old ATF to me) and stabilizer to fresh gas<br />Ran it for 3 hours on the water <br /><br />This motor/boat have sat around quite a bit, and i've kind of inherited them for the time being. I live on a canal, and have a 15 min idle/no-wake before i can get-to/come-back-from to the gulf.<br /><br />Last thing, if you could get a manual for this motor, which one is best? I am a fair shade-tree diesel mechanic, but this 2-stroke/carb/spark stuff has me a bit hesitant to dig in.<br /><br />Thanks in advance...
 

Hooty

Rear Admiral
Joined
Oct 2, 2001
Messages
4,496
Re: Merc 40 help for outboard newbie

For openers, I'd get a factory manual. If you can't find one on line, get it from your friendly Merc dealer. When you go past that 2/3's throttle and the engine wants to die, give the carbs a shot of premix with a squirt bottle and see if it picks up. If it does, I'd suspect fuel pump(s). Idleing a long time in your no-wake zone also gives plugs a chance to load up.<br />Try the squirt bottle first and if that don' do it, come back and we'll try something else.<br /><br />g'luck & c/6<br /><br />Hooty
 

MercN00b

Recruit
Joined
Dec 26, 2002
Messages
3
Re: Merc 40 help for outboard newbie

Hooty,<br /><br />Thanks for the response, but what you are suggesting is impossible for me to accomplish.<br /><br />The engine goes from running balls-out to dead stop immediately. It doesn't telegraph that its going to die at all, and when it does, its almost as fast as turning off the key.
 

Jim@KSC

Petty Officer 3rd Class
Joined
Nov 1, 2002
Messages
89
Re: Merc 40 help for outboard newbie

Could someone sit aft and continually squeeze the bulb?<br /><br />That would "pump" the pump.<br /><br />You could also substitute a known clean plastic tank with a new gas line and pre-mix, if you can bypass the oil injection.<br /><br />If it sat a while, the carbs would probably benefit from a rebuild kit. Clean the carbs in your dishwasher, but don't tell your wife.<br /><br />Good luck!
 

MercN00b

Recruit
Joined
Dec 26, 2002
Messages
3
Re: Merc 40 help for outboard newbie

Jim,<br /><br />Thanks for the suggestions. <br /><br />I was going to buy a new bulb and fuel line anyway, so I might as well do that this week before taking it out again. The boats 12 gal tank is plastic and removable, so i removed it and drained it. No silt or water visible. I'll fill it with fresh fuel before the next chance i get to run it. From what i've read here i gather that 87 octane pump gas should be fine. I'll be adding fuel stabilizer and decarb to that, since its doubtful i'll be using more than 5 gals, and the rest may sit for a couple weeks.<br /><br />Squeezing the bulb should be no problem while running wide open, so I'll try that too and see if it keeps running. <br /><br />I'm heading to the merc dealer today to pick up a manual if they have one in stock, if not will order the seloc manual online.<br /><br />One final question:<br /><br />The usual put-away routine for this outboard (prior to it coming to my house) was to run the engine with fuel line detached until it stalled. Being that this motor has oil injection (and from reading some posts here) that's prolly not a good thing, since a bunch of oil will sit in the carbs. The next startup produces lots of oil smoke, and dirty plugs.<br /><br />What is better for the engine? To sit with full carbs of fuel/oil with stabilizer, or should i run it dry and deal with the heavy smoking on the next startup?
 

Hooty

Rear Admiral
Joined
Oct 2, 2001
Messages
4,496
Re: Merc 40 help for outboard newbie

I'd just shut it down. I do that with mine and no stabilizer.<br /><br />c/6<br /><br />Hooty
 
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