Mercruiser 4.3 engine issues

[The Penguin]

Hi guys I have two problems with a 2000 mercruiser 4.3 300 hrs
1. oil leak I can't find it but theres a bit of oil in the bilge Any ideas of what may be leaking?

2 I was taking the kids tubing and when the engine was hot it ran on after the key was turned off- dieseling I think the term is
Any ideas?

Thanks

 

[Tanglefoot]

Ask your question here, lots of knowledge!

http://www.marineengine.com/cgi-bin/discus/discus.cgi?pg=topics

 

[opp-i-ottan]

A little bit of "greasy water" in the bilge is normal. Check LACK of oil in your engine rather than what the water in your bilge looks like. If you have to top up your engine oil often, you probably have a leak. I have a 2000 Merc 4.3, I have at least 300 hours on it and I just change the oil every year. Yes, the bilge looks "greasy" from time to time, but I have not had to top it up with oil yet!

The "dieseling" or, more commonly known as a, "run-on" problem could be serious because a severe "run-on" can actually cause your pistons to go into REVERSE - in which case you will "pump" saltwater into your engine through the exhaust! When that happens you can look forward to a complete overhaul and a lightening of your pocket book by about $5,000.00! (This actually happened to a friend of mine with an 8 cylinder Penta.)

The problem is caused by high idle speed and old spark plugs, and is easily solved with a good tune up and letting the engine idle for at least 5 minutes before you turn it off!

Inevitable tiny carbon deposits on your spark-plugs will start to "glow" (like ambers in a camp fire) when your engine is hot. If you turn your engine off immediatly after gunning it or keeping it on cruising speed, the "ambers" are still "glowing", causing the engine to fire even though the ignition is turned off. Like I said - this is inevitable!

Give your engine a good tune up regularly (change your spark plugs every year and use QUALITY plugs); monitor your idle speed (should be no more than 700 rpm's); and, MOST IMPORTANTLY, let your engine "settle down" by idling it for at least five minutes before you turn off the ignition! Idling well under 1000 rpm's will lower the temperature in the firing chambers on top of the pistons, and, if the spark plugs are relatively fresh, will cause the "ambers" to stop "glowing"! When you turn off the ignition - it should stop immediately.

Hope that solves your problems...

 

[The Penguin]

thanks very much guys I appreciate the help and ideas


The thing is I'm safe concious guy and I was tubing on sat with the kids and I was turning off the engine when the kids were in the water near the boat didn't want to risk an injury

 

[The Penguin]

So I found the oil leak - its the oil sensor on the right side of the engine just above the oil filter there's a tee fitting and two sensors the one with two wires on the end is leaking
get a bout a cup of oil after a day on the lake tubing etc.

looks like an easy repair going to find out how much a sensor is on monday - I was hoping it wasn't the rear main seal

Any how I'm going to change the plugs and check other electrical things in september/oct

 

[The Penguin]

So I found the oil leak - its the oil sensor on the right side of the engine just above the oil filter there's a tee fitting and two sensors the one with two wires on the end is leaking
get a bout a cup of oil after a day on the lake tubing etc.

looks like an easy repair going to find out how much a sensor is on monday - I was hoping it wasn't the rear main seal

Any how I'm going to change the plugs and check other electrical things in september/oct

 

[Barba]

On this site You can find tons of info about all engines,

he run the Merc shop and he is certified Mercury mechanics. Helps people for free all the time even with video instructions how to fix most common problems with boat engines.


http://www.themarinedoctor.com/cgi-bin/YaBB.pl

 

[Barba]

On this site You can find tons of info about all engines,

he run the Merc shop and he is certified Mercury mechanics. Helps people for free all the time even with video instructions how to fix most common problems with boat engines.


http://www.themarinedoctor.com/cgi-bin/YaBB.pl

 

[Mongoose]

well it sounds like you have a oil problem. with out oil your engine will get hotter and hotter and hotter and dieseling is also caused by the engine being to hot.

the spark plugs get red hot by the engine being too hot from lack of lubrication. and when you turn the key to turn off the engine it cuts out the electrical from giving a spark to the spark plug to engite the fuel so the motor shuts off but..... when your engine is running hot the spark plugs get really really dam hot and when a mixture of air and gas enters the combustion chamber it gets forced up by the piston and compressed and the fuel touches the red hot spark plug it doesnt matter if the electical is shut off because the gas will egnite and the process continues in all other cylenders.

but you should try to take the spark plugs and put new ones in there and because i bet they have some sort of damange but thats only if there not welded in and put some Anti-seize compound on the threads of the spark plug so if your engine gets really hot again the spark plugs wont melt and be one with the engine and the anti seize compound works up to 1500 degress and if your engine reaches that your boat is on fire. i hope its just a sensor not working.

 

[The Penguin]

no worries mongoose I'm smart enough to keep an eye on gauges oil levels etc I always check fluids before a run and the day before a run the engine never got past her reg op temp either

good idea on the spark plugs though

I will check em before the next trip and fix the sensor too

Thanks for your wise advice though always a good thing second opinions are

Cheers

 

[Monaro]

opp-i-ottan Your buddy with the hydro-locked pistons may have been able to save himself some cash. Normally if you have an engine run-on and get some water in the pistons you can cure your problem with a few simple steps.

Pull your spark plugs, both sides.
Run the engine over with the starter until all the water is pumped out of the piston.
Spay in a bunch of WD-40 in every plug hole.
Run the engine with the starter to pump out all the WD.
Repeat the last two steps a few times and your engine should be good to go.

This of course will not work if when you hydro-locked the engine in the first place you bent your connecting rods.

As to bilge water I run twin 4.3 engines with over 1100hrs on them. If there is a single drop of oil in my bilge I freak out. There is no reason for your bilge to have any oil in it at all if there is then you have a problem.