4.3L merc smokes, dies, starts hard... help please

[Priebe85]

I have an 89 Larson with a 4.3l Mercruiser. All sorts of problems. it was hydrolocked this winter. Now runs. When it is cold it starts fine in my driveway with muffs on. Sounds good, doesn't smoke. Then once it gets warmed up you can hear the engine start to run a little rough, kinda raspy. white smoke then comes out the pvc on the valve covers. also appears to smoke where the manifold goes into the tubing, can't pin point whats going on there. I go to turn it off at this point and it will continues "dieseling" for 10 seconds after i turned the key off. will fire back up but still runs like ****. When the boats on the water i have to have the trottle wide open for it to turn over. the motor does not overheat but seems like the oil is hot. Any ideas?

 

[Priebe85]

anyone?

 

[H20Rat]

explain the hydrolock more...? Sounds like you still have LOTS of water in the oil...

 

[Chris1956]

Did you fix the source of the hydrolock? A lot of times it is a bad riser or manifold. Sometimes it is a cracked block. My 4.3LX hydrolocked from a bad manifold to riser GASKET. The white smoke may be steam. If so, you still have a water leak into the combustion chamber.

 

[Maclin]

What does the oil look like on the dipstick? Is the oil level ok or high?

Regarding the hard starting, this sounds like the carb is flooding the engine with raw fuel, assuming it is a carbed engine and I am pretty sure it is. The carb can be spilling over from the fuel bowl if the needle and seat is worn or failed. Also there is a welch plug in the bottom of the bowl on some carbs, this is just epoxied in and the "glue" can fail over time letting raw fuel go directly into the intake manifold from the fuel bowl. If the flooding is bad enough the oil will be fuel contaminated, can tell by diluted grey color and strong fuel smell on the dipstick.

Look down the carb throat next time under the conditions when you would need the WOT to start. Don't start it, just remove flame arrestor and look down for wetness and lots of vapor or even dripping fuel.

 

[Priebe85]

Did you fix the source of the hydrolock? A lot of times it is a bad riser or manifold. Sometimes it is a cracked block. My 4.3LX hydrolocked from a bad manifold to riser GASKET. The white smoke may be steam. If so, you still have a water leak into the combustion chamber.

It was hydro locked due to antifreeze being dumped into the exhaust manifolds. Little mad at someone for this. But sat all winter like this. Had no idea. Hit the starter in the spring and it was locked. Took all the plugs out and drained the chambers. Now it starts. Thanks for all the replys. I'll try a few things after work. I've changed the oil twice now but sounds like I might have water in it still? Oil looks good and doesn't smell like fuel. Carb isn't wet either when is not running. I really don't want to have to tear the motor apart so all ideas are welcome lol. Otherwise I have a fun weekend coming up

 

[alldodge]

As Maclin mentioned, you need to run the motor then turn it off after it's warmed up some. Then look down the carb and see if you see fuel dripping or if it's wet. If it sits long enough all the fuel will dry up. The classic symptom of a carb flooding is the need to open the throttle to start the motor

 

[Scott Danforth]

It was hydro locked due to antifreeze being dumped into the exhaust manifolds. Little mad at someone for this. But sat all winter like this. Had no idea. Hit the starter in the spring and it was locked. Took all the plugs out and drained the chambers. Now it starts. Thanks for all the replys. I'll try a few things after work. I've changed the oil twice now but sounds like I might have water in it still? Oil looks good and doesn't smell like fuel. Carb isn't wet either when is not running. I really don't want to have to tear the motor apart so all ideas are welcome lol. Otherwise I have a fun weekend coming up

explain how the antifreeze made it from the exhaust manifolds to the combustion process?

did someone dump it down the exhaust runners? or into the cooling water jacket?

it sounds like you have either a bad riser gasket, or a bad riser or manifold.

which cylinders have water in them?