Mercruiser 5.0 dies when warm

[Jdeanmc]

Hi Guys
i have a 1999 SeaRay with a Mercruiser 5.0 , with the 2 bbl carb.the boat runs great and starts remarkably easy when cold, when its warm, and after we've sat anchored for a while,i usually slightly flood it to get it started.Ive been told to try to start it without throttle, it will not hit, so i give it a little throttle, no start, a little more throttle , no start and finally it will start, rev to about 3 grand , i pull the throttle back , smell gas but it then its running.
this ive learned to live with but lately its started dying once i give it throttle to get on plane. i can idle after start for a while or rev it up to clear it out in case it was loaded up, seems to make no difference.
When it dies it shuts off like its electrical but i have noticed once this happens if i pull the throttle back quickly , it will try to run but just slowly stall out like fuel related.it will fire right back up now, unlike when ive been sitting but sometimes this happens 3 or 4 times before it takes off and then runs perfectly.
Not sure if its related to bow rise before i can get on plane or "showering" down on the throttle to get on plane
any suggestions on what to look for and check?
thanks in advance

 

[Jdeanmc]

i found a # on the carb body, 861448, if this helps

 

[TurtleTamer]

That does sound like a carb/fuel issue. The important number for the experts on here would be your engine serial number. In order to diagnose a fuel issue, you're going to have to have a solid ignition system (full tune-up or recent tune-up history) and verified good compression on all cylinders. If it's been a long time since the carb has been rebuilt then it could be time anyway. You should also check your fuel/water separator.

Normally to start you may need to give the throttle a pump or two to get some fuel squirted in from your accelerator pump but you'd then pull the throttle back before attempting to start. You shouldn't start it with the throttle plates open and certainly shouldn't let it hit 3000rpm. If the boat has recently run then it should start with no pumps from the throttle.

What do you mean "dies like it's electrical?"

Bogging or dying when attempting to get on a plane also points to a fuel issue. But are you saying it'll do this a few times and then it'll get on a plane and run normally? I couldn't quite understand from your post.

 

[Jdeanmc]

Hi TurtleTamer,
First off, thanks for the reply and the solid advice, i will get the Engine serial number up, may be tomorrow evening before i can get it.
I did replace the water/fuel separator a few weeks back and drained the old one,no water that i noticed when i drained it.i just bought the boat last year and i don't know when the carb has been rebuilt, when its cold i pump the throttle 2 times and then pull it back, its starts perfectly, just when its warm do i have to keep inches the throttle forward to get it to hit
When i say it dies like its electrical ,i mean it just shuts off, light out.the first few times i thought i had pulled the kill switch switch out, but that wasn't the case, then i noticed if i pull the throttle back quickly when it dies , it does try to slightly pick up but it bogs down until it dies and yes after 3,4 or 5 times it will get on plane and runs perfectly to get us back in.
thanks again

 

[TurtleTamer]

You're welcome. But to me that's a bit odd when it dies like that. Only time that's happened to me, it WAS electrical. In what is a pretty rare occurrence, I had an ignition coil go out on me--twice in one season. Died like that both times, but with no restart. I wonder if you don't have a connection going bad somewhere that opens it a bit when it gets hot, in addition to a [possible] fuel issue that gives you hard starting.

 

[Jdeanmc]

i have wondered about the ignition coil, that's easy enough to eliminate, i purchased one at lunch, i'll swap them this evening and check connections.If that doesn't change anything i will at least have some comfort in knowing when it has been replaced.

 

[Scott Danforth]

its almost never the coil - as in only 1 out of every million coils changed actually needed to be replaced. once you open the coil package its yours (no returning electrical parts)

do you have fuel in the clear line to the carb?

your idle circuit in the carb is most likely plugged a bit

also, shutting off when pulling back on the throttle is the lower shift cable.

 

[Jdeanmc]

Hi Scott,
i will check the fuel line when its hot and shuts off, i have read about the fuel "vaporizing"just before the carb when it gets hot.
Also it has already stalled or died when i pull back on the throttle (in an attempt to keep it from dying)

 

[Jdeanmc]

Hey Guys,
Just to update on my stalling issue.
I ordered a carb kit with brass float and a new electric choke, just to have as many new parts as possible , cleaned and rebuilt it and the boats runs absolutely perfect now. when warm , i didn't even have to crack the throttle ,simply turned the key and it was purring like a kitten. planed out perfectly.
Thanks for the suggestions , i will assume it was a clogged idle circuit,
Thanks again for the replies
Dean