First post so here we go. . . I recently purchased a fishing boat with a Ted Williams / Sears 7.5 hp motor (I think it's from '73). We got the motor running before buying it although it did take a good 30 min or so of pulling before we finally got it going. The guy said he hadn't used it in a year and said there was probably some old gas in the carb. He put a new spark plug in and said he could smell varnish. (he did put new gas in the tank though) He said it ran great last season. When we finally got it going it ran well, we put it in and out of gear a few times, turned it off and on and repeated a few times and it seemed to run fine, just needed to shake the cobwebs off (or so we thought). So then I bring it to the lake to go for a joy ride and i get nothing, it pulls fine but doesn't turn over, it fires a couple of times but putters out. Any ideas on what I need to do to get it running smoothly/start? I brought it back home and pulled on the thing for an hour or so, adjusting the carb (it seems to have it's best pulls at 3/4 open), but still no luck getting it started. (yes, i had the intakes in water)
My buddy says just take the carb off, let it sit in Chem-Dip for 20 minutes or so, blow it out and it should work fine but i've read some horror stories on the chem-dip and i don't want to ruin the carb. Is this a good idea?
I'm definitely not knowledgeable enough to take the carb apart and get it back together.
There is a small tube shaped fuel pump in the carb. After you remove carb, you'll see it in the round hole. Carefully remove it, and check it for rips/tears. They are pretty common to fail. Also where fuel hose goes into carb, there is a plate. By unbolting the plate, you expose the flapper valve. If the flaps are hardened or stuck, it won't allow proper fuel delivery. Make sure you remove fuel pump, and flapper valve before you dip carb. It will ruin those pieces. Does your primer bulb ever go soft while running? Also check fuel fitting orings. My female fitting will leak fuel when disconnected. I posted a question right before you about my Eska 15hp. I have saved about 5 Eska's from scrap by fixing fp, flapper valves. Lastly check compression to see if it's ok. Those motors get a bad rap, but I like (and collect them). Good luck.
I used to run those engines also, a 3 HP and the 7.5. As pointed out, the usual culprit was the fuel pump element, a little red rubber 'balloon' that goes into the carburetor body. One tiny hole, and the fuel will not pump. I ALWAYS carried a spare in my tacklebox and got home from the boondocks several times as a result. The powerhead is actually a Tecumseh engine, and often the part can be located by your local lawnmower repairman, if Sears can't get it for you.
I would get a primer bulb (just to elimanate problems). You could be loosing the prime to carb (while you were on the way to the lake). That way, you can elimanate the fuel prime part of it. Alot of times (even if fp is bad, you can keep pumping th bulb slowly to keep it running. Then you can quit pumping, and if fp/flapper is bad it will die. Theese motors seem to need a few pumps of the bulb even if they sit for an hour. That's been my experience anyway. When I pump my primer bulb, I get fuel coming out of connector. I just ordered a new fitting for it. It will be here after lunch. It shouldn't let fuel come out while disconnected from motor. If it does this, it could also let air in. That's why my primer bulb is mushy I suspect. I have new fp/flapper valve (not installed yet). I like to do things one at a time, so I can learn which thing fixes it.
I'm not even sure there is a place to put the primer bulb (probably a stupid statement) but i have no idea where it would go. . . would it go on the carb? I tend to not think that this is the problem because when i close the choke and give a few pulls, it starts spitting a little bit of gas out so i assume it's obviously pulling just fine through the lines? not sure if it is relevant but the fuel tank is on the engine itself. . .
I should have asked if tank is internal, or external? Sorry for confusion. I have a Ted Williams (Eska) 7.5 that has both (internal, and external). You just turn a shutoff to one, or the other depending which one you are using. If it's built into motor, you don't need a primer. I would remove carb, and clean good. The center bolt that holds on float bowl (when removed) should have a hole that goes through the bolt crossways. Make sure that it's clear of any obstructions. Then remove float pin, and lift off float/needle assembly. Check float to make sure that there is no fuel inside it by shaking it. It happens more than you think. Also remove aforementioned flapper/fuel pump block. After you clean it, reassemble float/needle/float pin. Re attach float bowl with bolt. Make shure while installing float bowl, that the shallow part of float bowl goes underneath float hinge pin (so when float drops, it won't contact shallow part of float bowl). There is a small round screen behind flapper valve block (on carb body). Make sure it's clean. With flapper block reinstalled, hold carb upside down. Then attach a small length of hose to carb inlet. With your mouth, try to blow through hose (while holding carb upside down). You SHOULD NOT be able to blow through hose while upside down. Turn carb over (like it goes when on motor) then blow through hose again. You SHOULD be able to blow a little air through hose (when carb is upright). That will test that needle and seat seal. Go ahead and replace any rubber fuel hoses while you have it down to clean. Ethanol is hard on those hoses.