Won’t idle, won’t stay on - Maxum Boat Owners Club

Rambo · 06-07-2021, 04:20 AM

Hey, guys and girls, so I’m new to the boating world, so go easy on me lol. lots to learn, I’ve owned jet skis, very different. I need your help!!

So I purchased a 2008 maxum mx1800 with a mercruiser 3.0 4 cylinder last year, prior the boat sat for 3 year winterized, so I bought it because the guy wanted to sell it. On the way home I put fuel in it. Came home put the muffs on it turned water on boat fires right up. Ran great. Everything worked great did take it on the water because got it late in the season, and it need some cleaning. So then I winterized it. But I believe I put stabilizer in the tank. Antifreeze in the block. Etc.

Now this year I tired to fire it up, and I won’t stay on. Won’t idle. It has A two barrel carburetor, I gave it a couple pumps with half throttle and it fires stays on with 3/4 throttle, very rough idle. The second I put it back to neutral it dies. I also tried engaging the prop and I ran but rough and it dies. I had my brother pump the throttle so I can see the carb and before we tired to turn it on again and I only see one side on the carb is getting squirts of fuel When giving it throttle. But when we engage the prop then it get fuel to both sides. We did spark plugs And oil change prop oil is good the boat has very very low hours.

Can anyone be of some help the kids want to go riding lol. And help would be very appreciated. Thanks

mmwjr · 06-07-2021, 12:26 PM

You have a TKS (turn key start) carburetor which has no choke but instead an enrichment circuit, these are know for getting clogged passages. You’ll need to remove the plunger to clean it. I recommend that you get the Mercruiser manual for this carburetor.

Rambo · 06-07-2021, 12:33 PM

Hey, do you know where I can find a manual or download one? Also when you say “plunger” that must be in the carb?

mmwjr · 06-07-2021, 01:52 PM

I’ll look to see if I have the manual. Your pointing to it in the picture.

mmwjr · 06-07-2021, 02:09 PM

Try this place

https://www.scribd.com/doc/88364069/Service-Manual-41

Wallsy · 06-07-2021, 02:49 PM

Don't rule out a gas line problem (from tank to fuel pump even). I once had a 3.0 that behaved much like you describe and eventually determined that the flexible gas line insides had turned to mush apparently as a result of ethanol. Replaced the line and from that point on used regular leaded gas and never had another problem. This does seem less likely on a engine of your more recent vintage. Good luck.

Rambo · 06-11-2021, 10:18 PM

Okay so the tks part came in, I installed it and it’s still doing the same thing won’t stay idling, I even put seafoam in the tank gave it 2 pumps fires up then I have to give more gas to keep it from stalling the second I bring it to neutral it stalls. I ran it with a higher idle for like 2-3 mins then very quickly put it in drive then gave it more gas. Then I kept revving it so that the seafoam can work through the carburetor. But still stalls. I’ve done this a few times and then engine is getting hot so I stoped for now. Any clues

mmwjr · 06-12-2021, 02:10 AM

Quote:

Originally Posted by Rambo

Okay so the tks part came in, I installed it and it’s still doing the same thing won’t stay idling, I even put seafoam in the tank gave it 2 pumps fires up then I have to give more gas to keep it from stalling the second I bring it to neutral it stalls. I ran it with a higher idle for like 2-3 mins then very quickly put it in drive then gave it more gas. Then I kept revving it so that the seafoam can work through the carburetor. But still stalls. I’ve done this a few times and then engine is getting hot so I stoped for now. Any clues

Not sure what you replaced, the enrichment plunger?

That’s not the problem, you need to clean the passage in the carburetor body. Remove the plunger and spray carburetor cleaner into the passage. If that doesn’t work the carburetor may need to be fully disassembled and soaked in a cleaner then reassembled with new gaskets.

Phillbo · 06-12-2021, 02:25 AM

Why is the engine getting hot? Are you running it without water?

Rambo · 06-12-2021, 02:34 AM

Quote:

Originally Posted by mmwjr

Not sure what you replaced, the enrichment plunger?

That’s not the problem, you need to clean the passage in the carburetor body. Remove the plunger and spray carburetor cleaner into the passage. If that doesn’t work the carburetor may need to be fully disassembled and soaked in a cleaner then reassembled with new gaskets.

Okay I tried that, and that didn’t work so I’ll disassemble it tomorrow and have it soak in thanks.

Rambo · 06-12-2021, 02:35 AM

Maybe because I kept the idle higher than idle, and yes water on

Rambo · 06-12-2021, 02:42 AM

I also took the fuel filter out to replace that was well. So tomorrow I’ll have a new fuel filter and a cleaned carburetor.

So I have another question is this the fuel filter spot.
Because I took this out. And I was still able to start the engine and rev it

mmwjr · 06-12-2021, 12:21 PM

Quote:

Originally Posted by Rambo

I also took the fuel filter out to replace that was well. So tomorrow I’ll have a new fuel filter and a cleaned carburetor.

So I have another question is this the fuel filter spot.
Because I took this out. And I was still able to start the engine and rev it

If you’re referring to the white filter on the right hand side of the picture that’s the oil filter. If you ran the engine with it off oil should have pour out of the engine.

Rambo · 06-12-2021, 12:40 PM

So I’m referring to the black one on the left.

mmwjr · 06-12-2021, 07:27 PM

Quote:

Originally Posted by Rambo

So I’m referring to the black one on the left.

Got ya, yes I forgot the 3.0 have a fuel filter on the bottom of the fuel pump. So you ran the engine with it removed and no fuel came out where the filter was? Maybe there’s a check valve. There will be fuel in the carb so it will run for a few minutes if not getting more fuel from 5he pump.

mmwjr · 06-12-2021, 07:29 PM

When you disassembled the carb let it soak for several hours then use carb clean sprayed into all the passages followed by compressed air.

Rambo · 06-13-2021, 02:53 PM

OK guys thanks for all the help. What I did was take the carb completely apart let it sit in parts cleaner for a few hours cleaned it all up bought a new Excelerator pump new gaskets took the fuel pump out clean that out put it all back together the boat runs like a dream.

mmwjr · 06-13-2021, 06:30 PM

Quote:

Originally Posted by Rambo

OK guys thanks for all the help. What I did was take the carb completely apart let it sit in parts cleaner for a few hours cleaned it all up bought a new Excelerator pump new gaskets took the fuel pump out clean that out put it all back together the boat runs like a dream.

Excellent! Enjoy the season.