Idling issue

[Junior]

Hi everyone,

I am new to this forum and first time owning a boat, please bare with me. I just bought a 2004 Maxum 2400 SC3. I am having issue getting my engine to idle. It takes a bit to get it started and i have to push the stick forward a quarter way to keep the engine running. I tried watching some videos on adjusting carb and I sorta have it idling in Neutral but it is idling very high, if I turn it down, the motor would die. I tried taking the carb out and dip it fully in gasoline overnight, cleaned it and WD40 all the moving parts and its doing the exact same thing. Is it possible its just old gas? theres over half a tank in there. Please give me some of your advice.Thank you in advance for your reply.

[mmwjr]

Welcome aboard!

Could be old gas or a clog in the idle circuit of the carburetor which requires disassembly to properly clean it. Use carburetor cleaner and not WD-40. What rpm will it idle? Do you know if the boat was sitting before you bought it?

[Junior]

Hi Mike,

Thank you for your reply.

The 5.7l Mercruiser engine with 2 barrel carburetor will idle at about 1500 rpm.
I say about because the rpm gauge is not working. All other gauges are working. I tried to run it for 10 minuts with the water hooked up and noticed the temperature gauge was at 220. The boat had been winterized and was summarized by the last owner according to him before he sold it to me. He said it sat for about 8 months. I live in Vancouver BC Canada, so it wasn't terribly cold.

I will remove the carburetor and try to clean it inside with a carburetor cleaner like you suggest. Do you think I should get a rebuild kit from Amazon?

Thanks again,
Junior

[mmwjr]

Hi Junior,

That engine should idle around 650 rpm so you definitely have an issue. Yes I would get the carburetor kit as the gaskets will be dried out. I would get an IR temperature sensor to verify the engine temperature but you probably need to replace the impeller. You can also get wire cleaners on Amazon to clean out the small passages.

[Junior]

I ordered the rebuild kit today, should be here in a couple days. I had the carburetor apart and cleaned everything inside as suggested. I will give it a try as is to see if there is any improvements until the kit arrives. Is installing a new impeller a lot of work? I will look into the wire cleaner and keep you updated.

Thank you,

Junior

[Junior]

Just realized what you meant by wire cleaners. I don't know why I thought you were suggesting I clean my wires, lol. I did have some wire brushes and yes they work great for cleaning carbs.

Junior

[mmwjr]

If you have an Alpha drive the impeller is in it and the lower have is removed to access it. If a Bravo drive there is a belt driven pump. The manuals for both can be found under Documents of this site.

[Junior]

Hi Mike,

I put in the clean carb and started her up, she started right away and ran nice for about a minute and stalled. I then removed the fuel line from the boat gas tank and used a portable gas tank with new gas and it did the same thing, ran for about a minute and stalled. I also did fuel pump check and its working. The good thing is the rebuild kit will be arriving in about an hour. I will do the rebuild and let you know how it went tomorrow.

Juniorf

[Junior]

Forgot to tell you and don't know if it means anything. Just before engine dies, if I close the carb valve a bit the engine catches and runs again. Hope that helps you understand whats happening.

[Junior]

Also, I can't get to the mixture screw. There is a tamper proof cap on it.

Junior

[mmwjr]

Originally Posted by Junior

Forgot to tell you and don't know if it means anything. Just before engine dies, if I close the carb valve a bit the engine catches and runs again. Hope that helps you understand whats happening.

Carb valve? Throttle plate or choke plate? If choke plate by closing this you reduce the amount of air which in turn enriches the mixture. This means the engine is too lean. I believe those anti tamper plugs can be drilled out and this will allow you to adjust air fuel ratio but you need to verify this with your carburetor.

[Junior]

Sorry, I am not good with engine terms yet. I believe its called the choke plate, connected to the electric choke.
I was rebuilding the carb and when I removed the fuel inlet to replace the fuel filter, I noticed it was on backwards. I think this could be the cause of why it was running lean. I replaced it with a new filter in the correct direction.
After the rebuild, I installed the carb and it fired up right away and I also lowered the idled under 1000rpm. It seems to have lowered the temp too. I let it run for 10 minutes turned it off, waited for 10 minutes and turned it over again and she fired right up running fairly smooth. I will give it another check tomorrow cold. If all is well I will lower the rpm to about 700 rpm. I think we might have solved the issues.

Thank you for your help, I will let you know how it went tomorrow and doing a sea trial on Sunday.

Junior

[mmwjr]

Fingers crossed.

[2700Steve]

Hope your issues are sorted!

[Junior]

Thank you Steve, but I am still having issues.

[Junior]

Hi Mike,

I think you must have crossed your fingers wrong, lol.
So I went to started again the next day after the carb rebuild and installation. I think I must have flooded it. I can smell the gas and the engine has been coughing trying to start but no luck. I let it sit for 30 minutes, tried again and I did this a few times with same results. Thinking I must have flooded it bad, so I thought I should take out the plugs and check. That was a real bitch to get at the thing but I managed to get a couple out to check. They didn't look bad, not too wet and not too dark. Last owner told me he changed the plugs every year. I have been at it for a few days now, taking the carb out and putting it back and trying to do float adjustments, did all the starting steps and checks for starting a boat with no results. I am pretty stubborn but I am completely lost and out of my realm. I finally gave in and made an appointment with a marine mechanic. I will bring it in on Wednesday the 5th. I will keep you up to date. I am open to suggestions to try before the appointment if you have any.

Junior

[mmwjr]

If it is flooded try setting the throttle full open and try cranking it a fe2 times to see if it starts. This fully opens the throttle plate to allow max air to help lean the mixture. What is your starting process. For a cold engine I give a few pumps of the throttle and try starting. If warm just turn the key. If it just ran in the past 1-3 days it starts after two pumps. If longer I crank a few times then pump the throttle and try to start.

[Junior]

Hi Guys,

I thought before dropping the boat off, I will give it another go and yes I will try the Procedure Mike had suggested. I removed all the spark plugs, marked where each plugs goes and replaced all 8 plugs with new ones. I am also rebuilding the carb again with a kit. I have one question regarding the check ball. Is the ball supposed to be bigger than spring, this way the spring would be pushing the ball down before the T goes on top or is the ball supposed to be smaller and rolls inside the spring freely? The kit came with a ball that has a circuference smaller than the spring.

Thank you,

Junior

[mmwjr]

The check ball should not fit inside the spring.

[Junior]

Hi Mike, I have good and bad news. So the engine starts right away now with the new plugs and idles proper too. My issue is, theres a knocking sound now. Did I break something with all those false start you think. I only let it run for about 30 seconds and got worried.