496 hydroloc help. Help help
 

Plugs out can I roll it over with out disconnecting he ecu to prevent damage to it ?

so motor is a 2002 496 one of a pair in a formula cruiser.


water in 2 rear cylinders on port side . plugs out of the whole motor , riser off .

Question is can you crank it over without the wires and plugs atached.

will it damage the ECU without disconnecting it?

yes turn it over no it wont hurt anything

yes what?

I would roll it over by hand first then shoot wd40 in and give it a spin. If you have a teather just pull it out and hit the starter

so there is no way the water came from the riser as i can see as it is not a open design like i envisioned on the old 454 i am used to

is this year motor 2002 known to blow head gaskets it has 500 easy hours on it.

Does not have safety tethers.

Next idea?

With plugs out, This is a good plan, after that check your oil for milk.

just make sure the plug wires aren't close to anything and give it a turn.. When did you notice it was locked up?

i fired it up with the rear 2 cylinders plugs removed and it fired right up and blew water out

problem is i want to crank it and pickle it and i was thinking we are just drawing more water up through the outdrive intake and filling the cylinder again.

alarm intermintely went on and off after a short full throttle run.. i was not on the boat it is my buddies... they turned it off and it fired again no problem a few minutes later no crank hydrolock

Headgasket?

no water in oil no milkyness

Were you loading it onto a trailer when this happened. I have noticed when people get there trailers a little too deep and get the boat on it sinks the back way down in the water and a chance to let in flow in, doesn't mater running or not. and it fills both rear cylinders

1st Thought it sounds more like a cracked exhaust manifold or riser. Your not exchanging fluids. water to oil. AND a head gaskets has to be real bad to fill a cylinder that fast

nope just coming back to the slip

i think headgasket after a hard run. best scenaro intake.


is there anyway the manifolds or risers could cause this on a 496

What did the plugs look like when you took them out besides being wet. What color were they?

so you thinking cracked manifold ?



supposedly it has brand new manifolds no indication of water in the manifold when i pulled the riser

appreciate all the input

plugs clean just wet but i just glanced at them

need to crawl back down in the bilge to verify the plugs

Just trying to rule out the easy stuff 1st

do a compression test if you can, that will tell you

of course this is the one time my tool bags and compression gauge is not in the back of my truck.

compression check would be the 1st thing i would do if i had my tools

next step tomorrow thanks guys

so i will roll it over and wd40 the rear cylinders until

need to taste the water coming out of the cylinders time to crawl back down in the bilge

Don't forget it might give you a false high #reading because its a wet cyl. confirm with leak down.look close at the riser, spray brake clean on them, it helps bring up any cracking

Doesn't that have a closed cooling system? If so the only way to get water in is from the exhaust.

The 496 has closed cooling. If it was a head gasket or intake leak it would be antifreeze coming out of the cylinders and you would be low in the reservoir.

I had a friend that chased this same problem in his 2003 496 formula 330 sun sport. He changed manifolds , risers and starters , it would only do it once in a while. And then he finally listened to me and pulled the cylinder heads and and found the exhaust valves were not sealing and were causing water to be sucked back into the cylinder .

496's are dryjoint, you can pressure test manifolds without even pulling them........

Tommy , Those 496's are freshwater cooled , if it was a head gasket , coolant tank would be empty or it would have burst a hose. Are the manifolds new ? If they are the fact aluminum , they rot and dump water internally.
I know you said they have 500hrs on them , but the height of the standard elbow is right on the verge of being to low on some installations. Put enough fat asses in the back corner of cockpit and you could have trouble, especially if the motor is already having an issue. We put 6" taller elbows on our parasail boats with 496's after seeing our competition kill two motors this way. Good Luck!!!

Sounds like a leaking exhaust manifold to me.

You need to disable spark and fuel - Leaving spark plugs wires hanging is never a good idea

You say that like spark and atomised fuel in the bilge is a bad thing....

Dont listen to this joker,,,if you get the concentration just right you will no longer have hydrolocking cylinder problems....

on some of the 496's if the exhaust is to low and you pull back your throttles to fast I've seen water get sucked up right back into the engine and hydroloc them

intake leak almost always puts water in the oil or to the outside so it's likely not that

I'd pull the sea water pump belt while you crank the disabled motor. Cranking, without starting, can suck water up the exhaust if in the water or on a hose.

tommy,disable the ignition&fuel pump,like BUP said it is not a good idea to crank it with plugs out and system,s on.also,don,t put wd40 or brake cleaner in the cylinders.USE MARVEL MYSTERY OIL.

100% correct.the only way water can enter is through the exhaust.the block and heads have a antifreeze-water mix,not straight water.

Just disconnect the large connector on each side for the coil packs. That will disable spark and they are easy to get to.

troubles with small amounts of water in cylinders and on threads of plugs. And no apparent water leak in manifolds, heads, intake. Then problem may be reversion, reversion, reversion. Fighting that right now. Severe case in my boat. Big blocks have a lot of this issue. Mine are stock and just rebuilt both 2 years ago. pulling the heads already (only 2 years old with normal use due to reversion. Hopefully from just the valves, not bottom end. Merc has faught this forever. Look up the exhaust after idling and if you see many little light colored specs, thats the traces of water/salt water that is backing up in the exhaust when idling from REVERSION. Merc has made a "resonator" to put up the exhaust to correct this but may cost you 1-2 mph. But if it saves motors, worth it. Other better alternative is to weld on tubing to the elbows to get the end of the exhaust tubes further downstream before mixing with the water. Also slash cutting the tubes will help performance vs flat cutting them. A little bit of work but it would have saved my valves after only 2 years of service. A friend of mine has just done this instead of the resonators and completely stopped the reversion, and because of not using the resonators has lost no top end. I am going to do this on mine in next few weeks. I have also found just last weekend that the elbow temps are way to cold in fall, winter, spring even on the gulf coast where i live. THey are running 105 to 115 degrees and the manifolds are even colder. Causes bad "condensation". You can look up the exhaust pipes at the top forward curve of the elbow after stopping and see the water condensing. Need to stop that from happening. I am going to restrict the water flow to the manifolds to raise the temps after talking with Merc today. Simply put in a PVC valve and tinker with it to get the right temps without so little water of course that you burn the hoses. It doesn't take much water to keep hoses cool. If you need more water thru the block, just dump some overboard instead of restricting it. Again, put a valve to control it. Like i said a little work, but these motors especially mild ones, should run for many many years without rebuilding if corrosion does not get to them. Unfortunate, but no way around it. See many people with this problem that never realized what was causing it. Hopefully it may not be in your case, but thought i would share what experience i had. I just put in the resonators to try them temporarily but like i said, i am redoing the exhaust shortly. Some high perf manifolds may address this issue but no matter what brand i would inspect for reversion anyway. Headers should solve the reversion issue but they are a little pricey, and it not proper application wont help performance. REVERSION AND CONDENSATION .... not checked often enough and should be one of the first as its easy to do by looking up the exhaust with a bright flashlight. Get them corrected.

Turned out whomever worked on the boat and installed new manifolds before they bought the boat removed the flappers in the y- pipe . Reversion is what the cause was according to a Merc mechanic friend of mine who is familiar with 496s and repaired it.

I had this happen last fall in my 496. #6 cyl. Flappers in Y-pipe had broke loose and fallen down.