water entering cylinder on 470 mercruiser

[mcwinfrey8]

Does anyone know the path of the raw water after leaving the heat exchanger on a 470 3.7l mercruiser l4 engine? It enters the exhaust manifold (whih is also the filler tank for the closed water cooling). I'm wondering whether it could have a split inside, allowing water to enter no.3 cylinder. Any help with why i am getting water in this cylinder would be great this problem would be great. I'm pretty sure the closed system is good as new head gasket rebuilt cam etc etc.

 

[WillyBWright]

Re: water entering cylinder on 470 mercruiser

Water or Coolant? Seawater is pumped from the drive thru the voltage regulator into the heat exchanger and out the exhaust elbow. About the only connection is at the exhaust elbow if water is getting in there. If it's coolant, that leaves all the other possibilities. Fresh water would clean the sparkplug. Coolant would leave a white caking residue. (I'm not sure what saltwater leaves behind.)

 

[mcwinfrey8]

Re: water entering cylinder on 470 mercruiser

I'm almost positive it's the raw water, as when connected to a hose it runs fine at idle then after a rev goes down on 3 cylinders. switching off the raw feed whilst running brings it back onto 4 cylinders again in a few seconds. also, if i stop the engine without turning off the feed from the hose, when i restart it loses the 3rd cylinder again. Annoying!

 

[mcwinfrey8]

Re: water entering cylinder on 470 mercruiser

forgot to mention the plug when removed is wet with water.

 

[Haut Medoc]

Re: water entering cylinder on 470 mercruiser

I thought you would get more help by now....<br />The answer to your heat exchanger question is no..<br />If you had an internal leak there, you would lose coolant (anti freeze)....<br />I would suspect the riser or gasket if the closed part of the system is not losing any coolant....<br />I think it is a fluke that is going into #3 & not #4 as well.....If the riser is more than 7 years old, replace it....<br />At least there is only one ....JK