Won't start after engine flooding

[SoMD Terp]

Back for my second issue of the season. I made the rookie mistake of forgetting to close the raw water intake after a sail and came back a week later to find the engine flooded. After a few starting tries I was able to exhaust the excess water and the engine just sounded like nomal, but wouldn't start. Spark plugs looked in decent shape, compresson checked out good (thumb test). I drained the carb a few times and did find some debris and it was a bit milky the first 2 times.

At this point, my guess is that something clogged the jet in the carb and the engine isn't getting fuel. Thankfully I already have a carb rebuild kit, so that is currently my plan. I'll also be cleaning some extra spark plugs as a backup. Any suggestions to confirm carb before repairing it?

[ndutton]

What type of exhaust, waterlift, standpipe, straight pipe or waterjacket? Model boat might help too.

[SoMD Terp]

Boat is a 1979 Catalina 30. I haven't had it too long, so I'd have to look up the specific type of exhaust. It does not appear that the exhaust is blocked anymore.

[ndutton]

You saw where I was headed and by the way, the exhaust is a waterlift. Something is very wrong for an open raw water intake to passively fill the engine all the way to the combustion chambers and into the carburetor. In fact, so wrong that I'd be careful drawing source conclusions just yet.

The raw water pump needs to pass water without moving (!), the anti-siphon in the galley next to the inboard sink needs to malfunction (!!), the waterlift needs to overfill causing flow backwards into the exhaust manifold and into a cylinder with an open exhaust valve. The path from there into the carburetor is via an open intake valve meaning both valves in a cylinder are open at the same time and even if they were, how does the water get into the carb's float chamber (!!!)?

[SoMD Terp]

So if the engine did not actually flood, I'm at a bit of a loss. What would cause the engine to act seized, but eventually clear when water is cleared from the exhaust? And would result in something getting into the fuel supply (whether via tank end or engine end)? I don't want to clean up the carb and not have fixed the real problem.

[JOHN COOKSON]

May be a couple of things: Back siphoning from the exhaust system when the engine is warm and water in the fuel.
I don't think leaving the raw water valve open is an issue unless the engine is cranked with the raw water valve open and doesn't start???

TRUE GRIT

[Dave Neptune]

Terp, is there water in the oil? IE does the oil look milky? And did the oil level go up from the encroachment of water??

Dave Neptune

[The Garbone]

Can you get us a photo of the carb side of the motor and exhaust riser?

If you don't have the MMI manual it is a great investment.

My guess is bad fuel, have you drained/ replaced the water sep/filter on the fuel line. If you have a manual fuel pump there is a bowl that can be cleaned out also.

[sastanley]

Terp, again, I am nearby. I have not had a lot of experience with this particular issue..However, anytime next week I can make some time to come visit, after our sailing club finishes hosting our annual "Screwpile Lighthouse Challenge" regatta which is Fri-Sun. (like, after work next week..)

I will comment that my "limit" on cranking without starting is about 10-15 seconds..mostly this is because I am experiencing (2nd hand??) the effects from the P.O. over cranking and filling the #4 cylinder with sea water, with a result of reduced compression. So, I am really diligent about not cranking long so I don't make my situation any worse.

If I can help, let me know.

[jbsoukup]

if your anti siphon is not working and you close the raw water intake it will prevent the engine from flooding with water.
but that doesn't really solve the problem which I suspect is the malfunctioning anti-siphon.
water can reach the carb if the whole exhaust system fills and backs up through an open exhaust valve, filling a cylinder and (if you're really unlucky) leaking through a bad or partially open intake valve.
make sure there's no water in the cylinders before you try to crank it over, I've heard that bad things can happen to a hydro-locked engine