Detached carb, reattached, now hard to start. Reasons?

[RobH2]

I simply detached my carb and lowered it down. I placed a piece of paper towel in the throat to stop debris.

Then, I replaced my manifold gasket. I reattached the carb.

The engine is now extremely hard to start. After 4 or 5 grinds for about 3 seconds each, it will catch and runs great a full throttle. But under about 1/2 throttle it shuts off.

Once warm, it seems to start better but is inconsistent. Even warm, sometimes it is very hard to start but eventually always does.

I'm trying to diagnose and figure out what could be causing this.

[edwardc]

Check that the choke is still connected properly. Its real easy to pop the cable housing out of the friction clamp when moving the carb around.

[RobH2]

That's a very good suggestion. I'll go back and look at that specifically.

[capnward]

If it shuts off under 1/2 throttle, I suspect something in the idle jet. This happened to me, and when I took the carb apart, I discovered a tiny piece of crud in the jet. Blowing carb cleaner into it didn't work. It needed to be reamed out with thin wire. It was undetectable unless jet was removed and held up into the light to look through it.
When you had the carb detached was a good opportunity to take it apart, clean it, and inspect the idle and main jets.
Also check the two small holes in the carb throat. These are the idle discharge holes. When the throttle plate is closed, one hole is above and one below the plate. If those holes are clogged, the engine won't get enough fuel to idle.
When the carb is off is also a good time to replace inline fuel filters. When you drain the water separator filter, is there water in the fuel? Too much water in that filter will be passed down the line into the carb.
Make sure your idle screw is set correctly, 1 turn out from the seat. Turning it out makes the mixture leaner.
In my experience, ethanol fuel creates a brown goo in the fuel which clogs the carb orifices.

[RobH2]

I will look at all of those suggestions. I was in a hurry to get it running last week when I did the manifold gasket replacement, as friends were showing up so I didn't have time to pull it and examine it. It had been running perfectly and I have been using non-ethanol fuel. I also changed the water separator a month ago. It ran perfectly, no stalling and starting on the 2nd revolution. All of this "good" running was after I changed the manifold gasket. I have a new fuel polisher after the separator as well. It's just a month old.

Then, yesterday I went out, on my birthday no less, and problems. Hard to start, stall under 1/2 throttle, etc. But the last time I ran it, it ran so well. Something happened yesterday.

I'll pull it and see what's going on. Your suggestions are great and they should be done anyway just to make sure.

I'll post back what I find out.

[RobH2]

Instead of doing a lot of diagnosing, I just went ahead and ordered a rebuild kit, the small one without the jets, and rebuilt the carb. Pretty easy to do. The worst part of the whole job was access. My engine is mounted in a hole that makes it quite difficult to work on.

But, all appears to be well. Even with the carb and bowl being dry, it started on the first turnover. I was shocked about that actually. It idles perfectly at 800 rpm and seems to be all good now.

I don't know what got in it when I dropped it down to work on the manifold but now it's corrected. It was good to rebuild it anyway. It's one component that I hadn't torn apart or replaced since I bought the boat in 2010. I can remove it from the diagnosis list the next time the engine hiccups.

Thanks for the help. You guys are the best...

[sastanley]

RobH2, good to hear from you again! Glad you solved the immediate problem!

[RobH2]

Hi Shawn, thanks for checking in.

Yep, all good. I was kidding with a friend today and he asked how the carb rebuild went and if the engine starts better? He was out with me when it refused to idle and was beginning to malfunction. He helped me sail back into the slip since we had no engine by that time. I told him. "yea, it starts so well, that it starts 'before' I push the button."

It kind of blew my mind. After I rebuilt the carb, it of course had an empty bowl and was dry. The fuel line was also empty as I drained the small amount of fuel in it out when I removed the fuel line. After I installed the carb, I went to start it and was prepared to have to grind a bit until I got fuel flowing. But, incredibly, it stated instantaneously, no kidding, I don't think the crankshaft turned a full 360°. I couldn't believe it actually.

So, for now I think I'm good to go...lol...

Nice to see you and I appreciate the hello.

Also, I just noticed your signature about topside paint. I painted my decks last May, that was a chore, but the boat looks fantastic this year. New paint above the waterline where it can be appreciated sure is nice...