Staring problems for a 4.3l carbied Mercruiser

[Paulio]

Just wondering if anyone could diagnose or has had the same starting problems I am experiencing

When I cold start the motor it will fire up and run on idle but even when it has warmed up it wound take any more throttle it just dies. If you do get the revs up it will rev for a bit and then die again.

We took the are filter of and held the choke fully closed for a few second a couple of times and then it runs fine a didnt miss a beat all day. Which was good because we had to cross the bay head on into 25 knot winds on the way home.

Has anyone else had this on an inboard or knows what it might be. Pretty sure its starving for fuel but not sure why ?>:(

[wirlybird]

sounds like a small air leak. Buy the full carby kit for it. and run a decoking agent through the engine like yamaha tune spray then do an oil change should be right as rain.

[Roughasguts]

Probably water in the carby! by using the choke you sucked it out enough for it to run. So drain the carby and collect what ever dirt and water in a jar to see what's in it.

Have you got a water fuel seperator? has it been cleaned?


Cheers.

[testlab]

I second the full carby kit. Could be anything from a stuck needle to leaking bowl gasket. It's also likely it has had water in it at some time (as above) or a bowl full of dead fuel that's gummed things up.

If you wind up getting a replacement carb then make sure it is a marine carby for safety.

[captain rednut]

ill third the carby kit. cheers

[Paulio]

Thanks for all your advice.

The carby kit makes sense.

[Fed]

We took the are filter of and held the choke fully closed for a few second a couple of times and then it runs fine a didnt miss a beat all day.
Does it have an automatic choke and are you 'setting it' first?
Auto chokes do need to be manually set, the auto part is sort of auto off.

[Paulio]

Yes it does have an auto choke

Do you know how do I would find out about setting it ?

Also does anyone know if you can buy reconditioned carbys ?


Thanks

[Roughasguts]

If you wanted to replace with another........Probably better off with a Holly Carby!!!!

Cheers

[testlab]

Yes it does have an auto choke

Do you know how do I would find out about setting it ?

Also does anyone know if you can buy reconditioned carbys ?


Thanks

Setting the auto choke is done by advancing the throttle one full stroke and returning to idle position. The choke flap will engage and remain in the closed/set position until the bi-metal spring pulls it open. Advance the throttle 2cm and crank. Sometimes a single pump of the throttle will be necessary.

Once it is running and warming up (I warm up at 1000 rpm) and the revs rise by themselves a quick rapid burst of throttle will disengage the choke earlier than just letting it open by itself.

When I refer to advancing/pumping the throttle I mean with the gear shift disengaged. There are several ways of doing this depending on the control set you have.

[Paulio]

thanks again everyone

Ive been doing a bit of research and found this

"If it's an electric fuel pump I may know what it is-Ijust went through the exact same thing. Before you rip anything apart-
Check the circuit from the oil pressure switch that is teed off from the oil pressure sender on the port stern of the block. It is an extra switch-some merc techs call it a fuel pump switch, but techinically it's an oilpressure switch. There should be a purple and a purple and yellow wire coming out of the switch. You can test to see if the switch is bad by removing the wires from the switch and jumping them together. The switch is there so your fuel pump won't run if there is no oil pressure. I think the starter energizes the pump momentarily, but then this switch kicks in when there is oil pressure.
When I pulled my leads off, one of the tabs on the switch came with it-it was corroded. Mercruiser has since sealed the switch, so I guess I wasn't the only one.
I was pretty relieved it was something so simple-I hope it is for you, too.
If you have a mechanical fuel pump, well, sorry for the long post.
Goodluck"


I might check this option before re kitting the carby, I was quoted $ 500.00 for the carby work.


I will keep you posted

[testlab]

You should be easily able to check that with a test light or meter. What year model is the engine?

[Paulio]

Thanks again for all the advice, thought I would give you all an update for future reference. Turned out to be the wiring between the low pressure oil sensor and the fuel pump was losing voltage due to some corrosion on connections.
Boat was almost up for a service so I got Northside Marine to check over and diagnose and fix at the same time as gethe service.
Should be as good as gold now