Mercruiser 140 heat soak question

trobin0406

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The forum here has been a great help with my boat. I finally put on a new alternator and it seemed to solve alot of my problems. The only problem left is after cruising we stop for a few mins. I always leave the blower motor on and when I go to start it will sometimes be hard to start and other times it will start right up. If it does start right up i will give it throttle and within a few seconds it will start sputtering like it's out of gas. Sometimes it stalls and other times it will cough and catch and then continue to take off like nothing is wrong. It only does it during restarts. If I put the boat in idle and then take off again it will not do it. .. Could this be the gas evaporating? I rebuilt the carb months ago and used the gasket that came in the kit. Also when I bought the boat it appears someone cut a chunk of the metal going to the carb from the fuel pump and put in a rubber hose. Is it possible this is causing gas to evaporate in the line causing an air bubble?

Any help would be great!! Its a 1985 sea ray Seville with a mercruiser 140.
 

achris

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You need to get a steel line back in between the fuel pump outlet and the carb. It's steel from factory for a reason (safety). It's possible this line is leaking air, yes.
 

alldodge

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Don't think its evaporating but maybe leaking. Take a run and then stop as usual. Once stopped take the flame arrestor off and see if you see fog or fuel dripping in the carb
 

Bondo

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and when I go to start it will sometimes be hard to start and other times it will start right up.

Ayuh,..... Do ya give it any throttle, before ya hit the key,..??
 

boozer1966

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I had a very similar problem with a 1984 MCM 140 that I bought where a piece of the metal line had been cut out to add a fuel filter. Replaced the metal line and wrapped in in header tape. That helped, but the main fix was making sure that my impeller was in good shape. As it ages, I notice the water temp creeping up at idle speed. And even that modest temperature increase can make it very difficult to restart.
 

trobin0406

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Everyone's posts have been great. I will replace the steel line and see if it helps. Kinda sucks a new one is 50 dollars.

I have ran it on muffs and have not seen it leak after its shut off but will try this weekend.

I don't give it any throttle. I guess I could put it in neutral and 1/4 throttle and try. Everything else I have that uses a carb I have never done this but it's possible.

Temp does creep slightly. I figured this is normal since there is no flow when the motor is off but I am not sure how high. I know it never has gotten over 200. But will be sure to watch this over the weekend.
 

alldodge

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Not getting into other issues, but you can get steel break line from the auto store and use it.
 

trobin0406

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Does anyone know the size of the fittings at both the fuel pump outlet and the carb inlet? I was thinking of buying the parts before heading to the lake so i could replace and try this weekend. I found a premade line with [FONT=&quot]5/8-18 Inverted Flare Tube Nuts. Not sure if those would work. If not i can pick up the correct fitting and line and flare the ends at the lake.
Thanks!
[/FONT]
 

alldodge

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Sorry sure don't.I have at times determined what they are but can find nothing currently.
 

trobin0406

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Anyone else possibly know the fitting sizes on the carb inlet and the fuel pump outlet? Also the length of the steel pipe?
 

trobin0406

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Ok so I took the boat out this weekend after putting on a new fuel line. The boat ran great.... Until... We stopped for 5-7 mins. I turned the key on and the temp was at about 175-180. I gave a little throttle and started the boat. It caught and after idle for a few seconds we started to take off and then it proceeded to stall... I turned it over and it would catch then stall and we were trying to start for about 2 mins.. Finally it started and we took off no problem.

My initial thought is that it feels like the line that goes over the engine absorbs the heat and the fuel evaporate causing it to air lock and I have to keep cranking until it pushes fresh fuel.

Does anyone have any other ideas what this could be? I will try wrapping the fuel line in heater tape to avoid heat as much as possible. I can replace the impeller over the fall but feel it's pretty solid since it does go above 150 when its running
 

airshot

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I would be hard pressed to believe your fuel is evaporating in that short distance unless your engine compartment was really hot, and I mean really hot. I have a 3.0 myself with all steel fuel line and have never had this issue. Just reading between the lines here I think you may have a carb issue or an improperly adjusted choke plate. Did you buy a complete rebuild kit and do a "total rebuild' of the carb or a quick clean and replace a few gaskets type of rebuild? I good thorough cleaning is close to an all day job to let it soak and be sure all passages are completely cleaned out. A small wire is usually needed to get all the passages really clean along with a good airhose blow gun. You may want to check your fuel pump for proper pressure as well.
 

trobin0406

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It was a complete rebuild kit. I let it soak for 24 hours and then blew it all out. I also was thinking maybe I need the correct mercruiser base gasket. I have heard others have had a hard time with after market types. But I wasn't sure since I have idling issues turning the mixture screw to far in or out. Someone mentioned a leak but I have not witnessed this on muffs after running for 10 mins or so. I could try longer ride and watch but can't imagine a little gas would cause it to take mins to restart. I even tried pushing the throttle wide open during starting and made no change. It still took a little while to restart. also checked fuel pump pressure and it was 4-5 but will admit the gauge wasn't an expensive one so it's possible it was higher. I also have not had any problems and can run it up to 4500 rpm pretty quickly for a 4 cylinder.
 

alldodge

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Does the motor crank over quickly or a bit slower?
Is the choke full open?
Are the idle screws more then 2 turns out?

Having fuel pressure of 4 to 5 psi is good, but need to know what it is while running at higher rpms. Trying to figure out if your getting to much gas or not enough.
 

achris

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If you suspect vapour, get an outboard remote 20L tank, with a fuel primer bulb. Hook that up and run as normal. As soon as you feel the problem, give the primer a squeeze. If the problem goes away, you have a vapour lock or fuel pump problem confirmed. If not, start looking elswhere.

Chris......
 

trobin0406

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Motor cranks the same as it always has. The choke is wide open. I will have to check my idle screws but after i rebuilt it i set everything up to where the book said and fine tuned the idle mixture screw until it idled good and RPM were in range. I have not tried running the boat and checking pressure while driving but can try to do this over the weekend. I did notice Sunday morning that after a short drive i figured i would avoid the trouble of restart and just let it idle for about 3 mins. The temperature appeared fine when i went to take off and after a few seconds of picking up speed the engine started to cut out like it was about to stall. It was able to recover and we took off... It felt exactly the same as what occurs after a restart just not as intense and the motor was about to recover without completely stalling. It makes me think its not leaking fuel from the carb while its sitting because it idled fine the entire time. Should i try adjusting the idle mixture screw in or out more?

Not sure if that helps and any other ideas would great!!
 

alldodge

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Don't see the idel as being the issue, it does idle just taking off is the issue, so that's carb of fuel pump. As achris mention you could install a outboard pump bulb for testing, or check fuel pressure.

The accelerator pump is the issue in most cases or incorrect float level setting.
 

trobin0406

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Not sure if its accelerator pump since it only does it when sitting. i can take off and slow down multiple times during a trip and it doesn't occur. Just when i either shut it off for a few mins or let it idle for a few mins and then try taking off. I will try the outboard gas tank option this weekend and see if that helps.

Also just so i can rule this out what would be the correct thick base gasket for my carb? I know its a few dollars and figured it couldn't hurt.
 

trobin0406

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What should be the correct float levels? I dont want to take the carb apart again but if it fixes this problem i can. Its the only other thing i can think of besides vapor lock and fuel pump. And its better to start with cheaper things to fix first.
 

alldodge

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Read thru every post twice some more, and some of the points I noticed is, this is a Merc 140, so its a 1968 to 1986 model.
The issue is now when taking off, its only after it sits.
The temp does rise once the motor is off, but not above 180
The motor after sitting is hard to start and can stall and need to restart.

So to help I would like to know what year this is and maybe even the serial number

Scratch other things I might have mentioned, I'm leaning toward the float level is to high, or the carb is leaking fuel. The leak is either by the float valve needle, carb body or the float is set to high.

Can not say what the float should be set at because I have no idea what motor or carb you have.

Your motor is getting to hot while sitting, but right now I don't see this being your current problem.

Also don't thing you have a lack of getting gas, just to much so the pump bulb I don't think will help.

Last point, this is not vapor lock
 
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