Starting a Mercruiser 5.7 petrol engine

[planenews]

Hi all,
I have just bought a Fairline Sprint with a 5.7 Mercruiser engine. It has just had a major overhaul.
I can't seem to start it until several attempts with the obvious drain on the battery. Can anyone suggest a good technique for starting?
I have tried a few pumps of the throttle, non at all etc.

 

[AndieMac]

Hello and welcome

Has the automatic choke been disconnected?

Is the problem cold start or warm start?

Pumping (no auto choke) only works when really cold, once warmed up and during re-start, fully open the throttle (WOT), leaving one hand on it pushed right forward, and one hand on the ignition key.
Fire it up (this is where you need to be really quick), and as it starts (which it will) pull the lever back to idle.
This process is how you start a flooded engine, but it does allow a quick start with no guess work.

It may also need a carb overhaul, being an older set-up ingesting salt laden moisture.
crystals form around the bowl. Easy job to bead blast, re-onodise and new kit, ready to go for another decade or so.

 

[DAKA]

Hello and welcome

Has the automatic choke been disconnected?

I had a bit of string on my choke that I could hook on a convenient jubilee clip cutting the autochoke to 50% movement.
The choke was 50% disabled from may onwards.

Agreeing with AndieMac, check the autochoke, full choke is too much at this time of year and will flood the engine preventing start.

 

[Trundlebug]

Is the ignition timing set correctly?

Assuming the points gap is set correctly, the timing may be too retarded and need advancing a bit.
If you get a strobe light and check the timing, it can make the world of difference to starting, throttle response, performance and fuel economy. Just by turning the distributor to the right place!

Is the fuel fresh or old? As said above, fuel these days goes off after only a few months and fresh fuel can make quite a difference.

 

[andyo83]

Pumping (no auto choke) only works when really cold, once warmed up and during re-start, fully open the throttle (WOT), leaving one hand on it pushed right forward, and one hand on the ignition key.
Fire it up (this is where you need to be really quick), and as it starts (which it will) pull the lever back to idle.
This process is how you start a flooded engine, but it does allow a quick start with no guess work.

Seconded.

 

[ValleyForge]

All as above but remember - It has an engine driven fuel pump so you need to turn over for a few seconds to pump fuel from the tank into the carb. Then pump throttle 2 or 3 times to prime. Then turn over again. Hard to flood an engine of that size- should start promptly. If not take it back. Might be worth checking a few spark plugs to see if indeed it has new ones. (check gaps).

 

[spannerman]

Had the same problem with both my 5.0 and 5.7 V8's, the problem is after the last shutdown the latent heat causes the fuel in the float chamber to evaporate so next time you come to the start it from cold there is very little or no fuel present and it takes a bit of cranking to prime the carb, I fitted an outboard motor primer bulb to both my engines and when I do the usual check in the engine room I give it a few pumps and then it starts with out lots of cranking.

 

[planenews]

Thanks!

Dear all,
Many thanks for all the helpful comments. It has certainly given me an insight and I don't feel I'm starting "blind" now!

Mike

 

[lovezoo]

Maybe worth checking that the killcord switch isn't in the off position.

 

[dingdongs]

if it has just had a major overhaul i would take it back and get them to do it properly.find out if the compression is good for a start.

 

[gingie]

fuel

Have i mis read or not seen anyone suggest checking the fuel tap is open!!!!!

Fairline fitted valves to their boats worth checking.

It is very easy to flood any petrol engine even EFI! Regardless how many cylinders it has.

This engine MIGHT have a mechanical fuel pump which sometimes gets overlooked as the valves inside can stick/fail with age. Also some of the early ones also had a fuel filter arrangement on them. Again get over looked.

Or you could have a later engine fitted if your lucky that has an electric pump. This will run only when the engine has sufficient oil pressure. You can bypass the switch to override this sometimes these cause a non running issue.

Could also be a dead ignition sensor or coil if no spark present. Worth checking for spark.

 

[AndieMac]

Had the same problem with both my 5.0 and 5.7 V8's, the problem is after the last shutdown the latent heat causes the fuel in the float chamber to evaporate so next time you come to the start it from cold there is very little or no fuel present and it takes a bit of cranking to prime the carb, I fitted an outboard motor primer bulb to both my engines and when I do the usual check in the engine room I give it a few pumps and then it starts with out lots of cranking.

Good point with the engine heat/evaporation factor.

I've always had primer bulbs fitted to my old carb. model engines, sitting between the filter and carb itself, and also the new mpi recently has one grafted between the tank side of the filter and a retro fitted fuel manifold drawing from 3 tanks, just in case I need to manually lift fuel.

 

[planenews]

Thanks dingdongs, I will if it continues. Just wanted to sort out if it was me causing the probs!

 

[Jim@sea]

if it has just had a major overhaul i would take it back and get them to do it properly.find out if the compression is good for a start.

I suggest you do a compression test yourself, its really easy. Buy a compression tester, take the plugs out, disconnect the distributor so you dont get a shock from the ht leads, throttle closed, screw in the compression tester and check the readings, they should all be the around the same figure. If you dont have a compression then ring them up. If you let them work on it and they have made a mistake they probably wont tell you.