Hard Starting 4.3 V6 Mercruiser

[crawdog]

I have just bought a used Bayliner with a 4.3 Merc V6. It ran fine at first few times with a little trouble starting. Then after starting it would just fire right up on the next start, strong engine.... Ive been out 4-5 times and each time it was a little harder for the first crank. Ive been flushing and cleaning as required. Now it will not crank at all. Ive tried some starter fluid with no change. Looked at one of the plugs and looks good. Oil is fresh

one smoking gun. there was no inlet fuel filter on the carb. was missing.

Battery OK, starter keeps trying but no pop.

Some issues that it might be? Water in Fuel?, Carb not working properly? Fuel filter plugged? Spark plug gap? not the proper startup sequence( not putting it in the 1/4 throttle position. )

Im scratching my head and what it figure this out and do not want to take it to the shop. It should be something simple. I hope. thanks.

Ive been reading these forums for a while now and its been a great help with the fiberglass and deck rebuild.

what should I check out. Thanks for the responces.

 

[verado7]

Re: Hard Starting 4.3 V6 Mercruiser

check for spark - check distributer ,is it loose ? check timing , i'm betting the ignition module is bad though. good idea to keep a spar one of those on board too they are just like the ones in your truck fords are worse than chevy's though in regards to loseing ignition modules . now i've started something i'm sure .

 

[Silvertip]

Re: Hard Starting 4.3 V6 Mercruiser

You said you have the throttle set at 1/4 forward on cold starts but did you pump the lever a couple times to prime the engine before turning the key. Does the same thing as pumping the gas pedal a couple times on a carbed automobile of years gone by. Check choke operation. Remove the flame arrester and with a stone cold engine, open the throttle 1/4. The choke plate should be fully closed. If it is stuck open or does not close fully it is no wonder it starts hard. If this is a four throat carb, do not confuse the large secondary plates for the choke. Those are air valves. The choke is the single plate over the forward throats.

 

[crawdog]

Re: Hard Starting 4.3 V6 Mercruiser

Thanks for the help.

I changed the distribitor and rotor. It fired right up. Wahoo!!...... then two days later same symptoms of not starting but now Im not even geting a spark to the distribitor. I think your right its the ignition module but thats a $250 gamble and I want to make sure its the problem. Do Ignition Coils ever go bad?

Ive got 12 V on the + side of the coil in the Run position. is there a way to find out if the module has gone bad other than just replacing.

thanks again.

 

[cr2k]

Re: Hard Starting 4.3 V6 Mercruiser

A bad starter solenoid will cause this problem. There is a wire that runs from the starter solenoid to the 12v side of the coil. This is to boost the voltage to the coil during cranking. Yellow w/red stripe as I recall, but I could be wrong. Check for voltage during cranking. If not 12v then you may need to replace the solenoid or wire in a relay as I did for the same problem.

Easy diagnostic check...run a jumper wire from the batt to the power side (not the distributor side) of the coil and see if it starts. If so see below.

Inside the solenoid is a copper plate that makes the starter motor contact as well as the booster contact, this gets burned and dirty or the bolt end inside gets fried off and fails to power the coil booster wire.

If this is the case tap in to the wire that comes form the key switch at the starter run this to the activation coil on a relay. Run a 14 ga. wire from the + batt. terminal to one side of the relay and the other side to the wire that goes to the coil. About a $15 fix that WONT require starter removal. Dont forget to ground the other side of the activation coil. This will help but only prolongs the need for a starter and or solenoid replacment.

If this is not clear to you, email me at drydockmarine@comcast.net and I will send you a diagram.

Craig

 

[verado7]

Re: Hard Starting 4.3 V6 Mercruiser

another situation i would run across on gm distributors was the connector with bat wire on the side of the distributor - when you connect it it would sometimes push the inner terminal up instead of seating in it - take the cap off and reconect that connector while pushing down from the inside on the mating terminals - cheap fix if your having that problem - you could also go to a wreckers and grab an ignition module off a blazer or sonoma pick up or anything above 1985 for almost free and try it .also i just did a quick check and EBASIC POWER has them for 69.95 - dont be fooled by some touting them as special marine modules - identcal in every way to the ones mounted in cars . always a good idea to keep a spare one on board .

 

[cooter2506]

Re: Hard Starting 4.3 V6 Mercruiser

Verado he has Thunderbolt ignition FAR different they gm uses in their trucks