mercruiser 5.0 v8 carb hard to start

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rowey2006

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www.birdcareuk.com
hi,
having problems with engine it is hard to start and most times the engine floods, then i just walk away and come back another day.
batteries are fully charged, plenty of fuel, new fuel pump etc..
i leave engine for about 2-3 months between starts.

any help on this matter would be great.

thanks marc.
 
Marc - Need more info here. (I've two of 'em - I couldn't flood mine if I tried).

Sorry if it all seems bleedin' obvious to you, but how do you know it's flooded ?

How long from first turning her over does this take ?

Have you looked in the carb ?
 
hi dave
i am no mechanic, no i havent looked into the carb.
i only have the one engine.

i do the usual pumping of the throttle then try and start no success, keep cranking engine give it about 15 sec cranking then wait 20 seconds do this for about five six times then i give up on the thing, move the throttle a bit more etc.. does not start then i presume i have flooded the carb, engine bay does smell burning oil/hot type smell. i got the mechanic down last time he said the fuel pump was shot fitted brand new one about 4 months ago.
engine has been started after fitting fuel pump with no problems, could it be that it is cold very cold, raw water cooling.
regards
marc.
 
If it's left that long between starts it's no good trying to pump prime the cylinders as the carb bowl will have no fuel left in it to pump. Crank for 5 seconds or so with the throttle in neutral to fill the bowl, then give 3 - 5 brisk pumps of the throttle then open about 1/4 and try a start. Also whip off the fame arrestor & check if the choke is working OK
 
OK Malc - I'm no mechanic either, but I might have the answer for you.

When I first got my boat I had identical starting problems - I was certain I would flatten the battery before getting the engines to start !

Got the Mercruiser mech on - he said the following;

Winter starting - select neutral, pump the hammer all the way down and back again (still in neutral) five times to prime the carb. Turn over the starter, gently pumping the hammer half way down and back until she fires. Find a decent fast tick over speed (about 1500 rpm for mine) and leave for one minute. Then gently ease back the hammer as the engine sounds happier until temp's about 100F. Then sit the hammer back in its normal position.

Summer starting - as above, but should only need three initial pumps.

Problem is, the fuel gently seeps back into the tank when you're not looking ! Try this method first - it won't cost you any more than a trip to the boat. Let us know how you get on.
 
Marc, is the fuel pump actually delivering fuel? I had a problem with the Merc unit in my first boat - the (electric) fuel pump wouldn't work, we eventually traced the fault to a dodgy connection to an oil pressure sender located low down in the engine. Apparently the idea is that the fuel pump is only activated once the engine has oil pressure; if there's a fault with either the sender or the wiring to/from the sender then the fuel pump doesn't get power and the engine won't start.
Best of luck with the debugging.

Cheers
Jimmy
 
These engines are hard to start at the best of times, let aloneafter being left for so long between running periods.

As others have said - check fuel is getting to the carb, and for operation of the choke.

Also, clean out the fuel filter and new element. If these collect any water, then engine will not start or run well.
 
My 7.4l V8s have always been hard to start after standing for a few days; I have to pump the throttles about 10X, but they always start. The manual says after starting set at 1500 rpm until engine temp reaches 130F. I've had my chokes removed as in this climate they're a bit redundant. It improved fuel consumption a bit, too.
 
I had problems with the Auto choke.

Make fast a bit of string with clove hitch and tape.

Once flooded force open choke ie/ no choke.
Then start .

It worked well for me.
 
Those Merc V8's "flood" quite easily.

The suggestions above are quite correct, a couple of quick "pumps" then bring it back to just above tick-over, crank it over and gradually increase the throttle till it catches, then warm it up by idling it at about 1,500rpm for a bit.

However, if you "flood" it (total resistance to starting and often a smell of petrol) then applying full throttle (obviously whilst in neutral) and holding it there whilst cranking will scavenge out the overfuelling and it will eventually stutter into life. You need to be a bit persistant and don't stop cranking the instant it starts to go as it usually splutters a bit.


As soon as it does go you need to wang the throttle back quick otherwise you're instantly revving the nuts off of a stone cold engine that the oil hasn't properly got round yet, not good. Pull it back to a fast tick-over and then let it warm up as normal.

Got me out the you-know-what a few times with big V8's that tip has.
 
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