Any Boat Mechanics On Here ? Merc Problems!g

[Insanity]

So I bought this little 7.5 Mercury from my land lord it a 1976 model but has only ran about ten times.

Looks like new. It has a 125 pounds of compression. And the carb is spotless I have cleaned it three times. ( completely striped it down jets out, carb cleaner and air blew threw everything, and a new fuel pump ) I'm not new to carbs. It should run. Still could be the problem but I don't see how.

I changed the port side gasket as I had a leak and it was running lean and screaming.

But it still will not start at all unless it's in gear and wide open. I have ran it like that and it skips the throttle up and down every so often without you turning the throttle. That's with the throttle wide open it will drop to half on it on then back to wide open. About three times then it will run wide open as far as you want to go.

When you idel down it will go pretty low ( while missing ) then die. And will not start back unless wide open.

Now I took it to another guy to fix and it ran fine for him. ( my step father watched from the bank said it purred like a kitten ) So something is really weird. When I got it back I choked it and it started rite up. I un chocked it and it ran wide open idel as I turned it down it just died. And then got harder to start until it would start anymore. Turned the throttle wide open and it started first pull. So it's not flooding.

The boat mechanic up the road is very behind. And I can't drop it off and wait for it to be fixed in three weeks or so. I've got fish to catch.

Oh and I already put in a new impeller!

[Insanity]

OK any half way mechanics. Lol

I'm lost need ideas of things it could be. To like at.

[gardnerjigman]

Did you ask the first guy what he did??? Maybe run it half choked?

[Smokinal]

sounds to me like a piece of debris in the bowl. does that carb have the little orifice in the bottom of the bowl where the jet screws into? take a straightened out paperclip and jam it through the jet a few times.  i had an old johnson with same exact symptoms and thats what my issue was.

keep us posted.

[Insanity]

We both ran it the same. Choked once and then it started. and he used my gas tank to boot.

I sprayed carb cleaner and air threw every jet. And even looked threw them the second time I took them out. On the third attempt to find the problem I remove the main nossel which the Manuel says not to do. I figured out why when I went to put it back together. The venture fell out of place. Took a little while to get that little bugger poked back into place.

I think the main nossel is the jet your talking about. Smokinal. It has two rows of little holes around the top of it. I poked them out with a needle because I couldn't line them up to see threw them very good.

If I just new it was the carb for sure I'd buy a new one. I'm so sick of taking the old one apart. Lol

I've had it off like nine times for on thing or another. I'd love to hit it with a hammer.

[Tim Kelly]

If it's a twin cylinder engine it sounds like one of the cylinders is only firing intermittently.

[Tim Kelly]

Actually, I had a car that used to act similarly and it turned out to be the points closing up. Since the days of electronic ignition the points and condenser have been done away with, but if you have points in the distributor then check the gap and maybe replace them. 

[Insanity]

If it's a twin cylinder engine it sounds like one of the cylinders is only firing intermittently.

Yep its a twin. I was wondering about that. The motor has barely been used. But I'm wondering if the coils dry rotted. Or something.

It's got a heck of a spark when I checked. But could be changing. I don't no how to run a multi meter enough to test them.

I was going to check the points but can't figure out what threads are in the flywheel to pull it. If it has points. It say thunder bolt ignition. Sounds like something that wouldn't have points. But it is a 76. I'd think points