Mercury 150HP inline6 Water in Cyl 3

[acdcbcwhatever]

I have water in cylinder three, have taken off the intake cover, exhaust cover, and water cover over the head where the plugs screw in. I can't find any cracks, the motor doesn't have a headgasket. I figured it might be towards the back of the motor, as the reeds are on the crank in this motor, and I have water shooting out the carb too in little drops. Any help would be appreciated. Motor was rebuilt not that long ago, it has been ran in saltwater, with no water running through the motor, it runs like a raped aped, hook a hose up and it lags on the rev up. In gear it stalls immediately in the water. Also, in my book it shows a restrictor underneath the intake covers. Any idea what this is?? Looks like a plug. Is it in every cylinder port of the intake? Sorry don't have the boat right by me now. The book justs says to put it back when you rebuild the motor, doesn't say anything about who or what it is.

Thanks

 

[Chris1956]

Re: Mercury 150HP inline6 Water in Cyl 3

Idle restrictors are small bead-like plastic inserts that fit into the holes drilled in the block under the transfer covers. They are of marginal value on a well running motor, and no value to you at this time.

Normally the water will come in via the inner exhaust cover or exhaust baffle. Remove these check them for warpage and reinstall with new gaskets and a moderate amount of red silicone. Torque them properly.

 

[acdcbcwhatever]

Re: Mercury 150HP inline6 Water in Cyl 3

Thanks for the info, that's what it said in the book too. If it is coming through, how would the water enter the motor? Through the exhaust ports? All the other cylinders are burning good with no water in them. Also one other question, theres a water jacket cover right by the exhaust ports. I haven't taken that off yet, everything else looked good.

 

[Yepblaze]

Re: Mercury 150HP inline6 Water in Cyl 3

What did the spark plug look like at the business end? Brown? Black? Gooey? Like new?

 

[acdcbcwhatever]

Re: Mercury 150HP inline6 Water in Cyl 3

It was grayish from oil and water mix, along with water bubbles on spark plug. I work on cars so I know what it looks like, just becoming familiar with boat motors. Also, when the gas and water spit out the back of the carb from the dead cylinder, it's more of white like the oil mixed more with the water. It's only on the middle carb, and water only in cylinder number three. Also, when I had it on the lake last time, I pulled the number three spark plug and ran it for a sec like that. Ran like a five cylinder motor. Pulled off just fine.

 

[Faztbullet]

Re: Mercury 150HP inline6 Water in Cyl 3

Never use silicon or any sealer on exhaust baffle and gaskets!!! Clean and check for warpage as suggested...replace if warped. Clean bolt holes with tap and NEW bolts and high temp epoxy on bolts

 

[Chris1956]

Re: Mercury 150HP inline6 Water in Cyl 3

Whatever, Check the inner exhaust cover (by the exhaust port) for corrosion holes. There are some nooks and crannies, so look it over well. With the severity of the water infiltrasion you have (spitting out the carb), you should see a hole in the exhaust baffle or inner water jacket cover. If not, it is possible that the inner water jacket cover is leaking. Be careful removing those bolts. They break easy, and ate a bit*& to retap. Use heat and penetrating oil and an impact driver to get 'em out.

BTW - The last 150HP inline six was made in 1977. I have one that threw a rod last year....