Mercruiser 260 HP Water in Cylinders

[Hot_For_Mula]

Hey everyone,

Brand new here hoping to grab some advice from you all. I've been reading for the past week previous stories of similar nature, just looking to get opinions on my specific situation.

Last weekend I took out my Formula 233 with the 350 V8 merc. First run of the season. Puttered around at just over idle speed for about a half hour. Shut it off and drifted for a little. Fired back up and drove another 20 minutes then shut it back off to go swimming for an hour or so. Went to turn the engine back on and head back and the engine wouldn't turn over. I suspected a dead battery and ended up calling the sheriff. When their battery pack didn't solve it, they towed me back to the launch and helped me get her up on the trailer again.

I failed trying to crank it by hand so pulled the plugs and found water in all 8 cylinders but no water in the oil. Cleared it out and sprayed WD40 in the cylinders and spun the engine around a bunch without issue.

I'm suspecting an issue with the exhaust manifolds or risers. I'm stumped by it effecting both sides. I filled the manifolds with water through the hoses and couldn't find any leaks, cold that is. I left the block full of water and nothing leaked out as well.

Love to hear some thoughts. I'll pull the risers next but what should I look for as far as failures besides on the gaskets?

Thanks

 

[Scott Danforth]

get the motor dried out ASAP. get it fired up on the muffs and run it for a bit.

is this a salt water or fresh water boat? new to you boat, or have you owned it for a while.

hope you have gotten it running and not sitting for a week with water in the bores (if so, pull the motor and throw away today, buy a new motor)

if fresh water, your flappers could be damaged, your boat could have extra weight in it (water logged foam, more people than it should, etc.) which would shorten the riser height to water-line dimension

if salt water, your manifolds or risers could simply be rusted thru.

 

[TyeeMan]

I had the same thing happen with a 4.3L V-6 about 3 years ago. Took the wife and in-laws for a cruise one Saturday morning, she ran like a million bucks as usual. It was a warm day, pulled out, dropped off the wife and in-laws and headed to another lake to go swimming. backed the boat in, hit the key and nothing. I mean I could tell the starter bendix was engaging but the motor wouldn't turn over, , not even a couple degrees. I tried turning by hand by grabbing the alternator belt in one hand and turning the alternator with the other, nothing! Wouldn't move a bit.

Thankfully, having spent much time on this fine website reading, as soon as I got back to our camper (up north in the woods) I pulled the plugs and got a bunch of water out of 2 cylinders (opposite banks) and a little out of 2 more.
I cranked it over to clear the cylinders and sprayed a bunch of oil in each cylinder and rolled it over. The oil looked just fine by the way.

Figuring the age of the boat (1995) I just went ahead and ordered new manifolds and risers.

Once I got those installed I ran the engine on the muffs for about 10 minutes and immediately changed the oil, , did that twice. After installing oil and filter the 3rd time I went to the lake. I bet I had moisture on the oil fill cap for the next two hours. Oil looked nice and clear but there was moisture somewhere.

Ultimately I saved the engine. Whew!

No pun intended, but that was sinking feeling when that engine didn't roll over. You can just see the dollar signs start ticking away.

Good luck!!

 

[wahlejim]

Based on what you have described, I would go through your entire exhaust system to search for the problem. It is not air tight somewhere. Some common failure points are gaskets (between the engine and manifolds and between the manifolds and risers) hose clamps, hoses, and shutters.

 

[Bondo]

Some common failure points are gaskets (between the engine and manifolds and between the manifolds and risers) hose clamps, hoses, and shutters.

Ayuh,.... There's No water There,... Just exhaust, 'n the outside,...

HFM,... Welcome Aboard,.... If this motor has ever run in the brine, the intake manifold is also suspect,....

 

[Rick Stephens]

Don't assume you do not have water in the oil if you are going by the dipstick. It will not show water, especially when it hasn't been run with water in it. You could have quite a bit in the bottom of the pan and none would get on the dipstick which is isolated in its tube. And the water won't have mixed with the oil to create a milkshake since it froze up.

As everyone is asking, is your boat ever in saltwater?

Seems that going swimming, lots of folks on the stern, often times is the cause of water getting up and over the risers into the manifolds. Shutters won't stop water from getting in from a continuous low stern from folks climbing up and down and congregating there.

 

[Hot_For_Mula]

Thanks for all the replies! I was pretty quick to clear out the bores and coat everything with oil so hopefully the motor can be saved. I'll do and oil change asap and get it fired up. It's a fresh water boat only. Family owned from new in 1982. I rebuilt the motor a few years ago with dart heads and a comp cam. The original heads were actually getting thin on the water jackets. It was only my girlfriend and I at the time and we spent very little time on the swim platform, additionally it just came out of storage so no water logging so I don't suspect it was backwash. I guess manifolds and risers should be done. Its been at least 6 years on those but the boat has seen maybe 20 hours of total use in the last 3 years. I just found it difficult to belive they would both go at the same time especially without indication of the engine running poorly.

Thanks again!!

 

[Rick Stephens]

I can't imagine a low use freshwater boat needing manifolds. Mine are 25 years old and have a thousand hours on them. I agree, should be something else.

 

[96RinkerCaptiva212]

Having just replaced a 5.7 from water in the cylinders, glad you found the problem and got the water out quickly!! I would also suggest to not go by the dipstick as that is what I did and it seemed fine. Didn't pull the plugs until 2 or 3 days later and had water in 2 cylinders. I pumped the oil out through the dipstick tube and it was a milkshake (even though dipstick looked like clean oil). Check your exhaust flappers. Like someone else said, they aren't going to be 100% "water tight" but they certainly help. I found mine still intact but they were laying wide open from age, so they were not stopping any water from entering upon an abrupt shut down (tubing with kids, idle zones), or... too much weight on the stern.

I see you are up and running but just keep an eye on the exhaust situation. Next time you have a few people out on the stern, check the risers compared to the water level. Avoid abrupt shut downs as the subsequent wake coming into your boat can shove into your exhaust somewhat. As cheap as flappers are, it's worth a check and replacement if they aren't strong. Mine was a 96 with 340 hours and the flappers were dead. They are a good safety net, if anything.

 

[Hot_For_Mula]

Just to come full circle on this. I removed the risers and inspected them thoroughly. It appears that the water jackets themselves are fine, as is the same on the manifolds. The mating surfaces between the risers and the manifolds however were extremely wavy due to corrosion. I machined the riser surface flat and filed the manifolds for a while to flatten those out again. New gaskets and the problem appears to be solved. I replicated the same usage and did not have any issues. Hopefully that is the end of this particular saga. Glad I seem to have saved the engine.

Thanks for the help everyone!