Won,t start when warm

D

dsantos

Member
Joined
Jul 10, 2001
RO Number
5266
Messages
188
Motor – 1986 Mercruiser, raw water V8 I/O – newly rebuilt.

Issue – Boat starts great every time on muffs, once in water and ran for about 30 minutes temp around 150, if you shut the motor off it will NOT start.
It cranks over but will not fire, after several cranking attempts the motor gets harder to turn over because the compression increases. On 2 occasions while cranking fluid (gas I presume) was sprayed out of carb.
Eventually the battery can no longer crank the engine over, towed back to dock, after boat is home(battery charge)turns over easily and fires right off.
 
Is the choke open or closed when you try to start warm? If closed, try holding it open and turning it over. could just be the choke is out of adjustment.
Jim
 
Electronic choke and is open when warm starting. Could it be flooding bad enough to almost hydro-lock with fuel?
 
Rochester carb? Well plugs may be leaking. and yes, it's possible to hydrolock from gas and even fill intake manifold with gas. Also look at tube from fuel pump to see if it has gas in it. means diaphram is broken/torn and leaking gas directly into carb.
 
Tonite i let it run for a 1/2 hour one the muffs,was able to get to not start,and crank over slow. Pulled sparkplugs to check for water, none plugs did smell of gas. Not sure what to check next, guess will check for spark in case the ingition sensor is not functioning when
hot.
 
you can delete three of the four duplicate posts.
 
Did you at least check that fuel pump over-flow tube.

...and a choke stuck closed WILL suck large amounts of gas...especially if the throttle is opened while starting to start.
 
When hot, with no pumping at all and no attempts to start normally but throttle fully open, will it start?
 
The first thing to do when it won't start is to check if it is sparking...with a $10 spark tester. If not, all the fuel work is premature. Ignition can go bad when it gets hot. What king of ignition....points or electronic? When it doesn't start, does coil have 12v? Does it fire once when you turn the key off? It's cranking slower because the battery is discharing, normal. Don't overheat the starter and burn it out. Less probable is a heated fuel line vapor locked.
 
Google Thunderbolt IV ignition module and you will have more answers than you care to read. I agree with others that it is not likely fuel problem but more likely the module or the coil.
 
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