What could be the damage

[sarbog]

A little long but yesterday started out on my 340, 8.1 Horizons. Have had no trouble all year. At NO Wake speed for about 20 minutes to the inlet past the port. No problems. When I got to the end of the NO Wake zone I throttled up. within about 10 seconds it just didn't sound right, but water pressure and engine temp, RPMs, all normal. a few seconds later I smelt something burning. Turned around and white smoke pouring from air vents on starboard side. Almost instantaneously vessel view alarm goes off and engines go to emergency power down. all pressures and temps still good. I shut both engines off, powered everything off I could think of, as with all that smoke I immediately suspected an engine room fire. Looked and no Halon system discharge but noticed my bilge pump light was on but it wasn't running. Also, When I shut the engines off the smoke dissipated. I also immediately got on my handheld VHF (as I had shut anything electrical off) contacted Tow Boat and Coast Guard about possible engine room fire. Coast Guard arrived first within minutes. They will be getting a letter of thanks for their quick, professional, courteous, and calm reaction in, to me a highly stressful situation. Anyway, When we opened the hatch, with extinguishers standing by there was no smoke but noticable water in the bilge. Tow Boat passed a pump and pumped it out and not taking on any more water. What we found when towed to port was a clamp let loose on the raw water exhaust hose so it was pumping into my bilge. Probably blew when throttled up.

My question is, does anyone have any thoughts on what the smoke and burnt electrical fire smell was from and what else may be damaged? Engine was getting water fine from the intake but outflow was into the bilge. This was the starboard engine. As I said bilge pump light comes on but pump doesn't run and new pump in the spring. Can't get a mechanic to it till tomorrow. What got burned up?

 

[Strecker25]

A little long but yesterday started out on my 340, 8.1 Horizons. Have had no trouble all year. At NO Wake speed for about 20 minutes to the inlet past the port. No problems. When I got to the end of the NO Wake zone I throttled up. within about 10 seconds it just didn't sound right, but water pressure and engine temp, RPMs, all normal. a few seconds later I smelt something burning. Turned around and white smoke pouring from air vents on starboard side. Almost instantaneously vessel view alarm goes off and engines go to emergency power down. all pressures and temps still good. I shut both engines off, powered everything off I could think of, as with all that smoke I immediately suspected an engine room fire. Looked and no Halon system discharge but noticed my bilge pump light was on but it wasn't running. Also, When I shut the engines off the smoke dissipated. I also immediately got on my handheld VHF (as I had shut anything electrical off) contacted Tow Boat and Coast Guard about possible engine room fire. Coast Guard arrived first within minutes. They will be getting a letter of thanks for their quick, professional, courteous, and calm reaction in, to me a highly stressful situation. Anyway, When we opened the hatch, with extinguishers standing by there was no smoke but noticable water in the bilge. Tow Boat passed a pump and pumped it out and not taking on any more water. What we found when towed to port was a clamp let loose on the raw water exhaust hose so it was pumping into my bilge. Probably blew when throttled up.

My question is, does anyone have any thoughts on what the smoke and burnt electrical fire smell was from and what else may be damaged? Engine was getting water fine from the intake but outflow was into the bilge. This was the starboard engine. As I said bilge pump light comes on but pump doesn't run and new pump in the spring. Can't get a mechanic to it till tomorrow. What got burned up?

Is it possible the white smoke was steam? Not sure how you're plumbed but if that was the manifold/riser discharge hose I would imagine rubber exhaust boots/hoses got hot and caused some of the smell and maybe the spraying raw water hitting the hot metal caused the steam?

Did the alternator get very wet/submerged? We had an alt get submerged once and caused a nasty smell. It ended up needing to be replaced

 

[Air O'Nautical]

Sounds like you did you good job Captain.

Not really possible to diagnose not knowing what got wet....but, shouldn't be too bad.


I'll take a WAG (wild-ass-guess) at it....

The smoke was only steam from the hot engine getting wet from the raw water spray.
The burning smell was the big hose after the exhaust manifolds starting to melt from the excess heat because the lack of cooling water....and possibly the serpentine belt getting wet and slipping/burning.

I'd inspect/replace both big exhaust hoses between the engine and muffler can.
Same with the belt.
Same with the bilge pump.
Same with the alternator if it got wet.
Check every electric connection that may have gotten sprayed with salt water, spray with WD40 and coat the connector seals with dielectric grease.

Carefully rinse the engine of any salt residue, knowing not to spray water on anything electrical.
Check all clamps on both motors to prevent it happening again..

Good Luck,

 

[Henry Boyd]

A couple of seasons ago we had one of the manifold raw water cooling manifolds crack (the second piece to the older 496/8.1 two piece exhaust manifold). That did result in a lot of water in the bilge and steam. But the loss of raw water cooling was not sufficient to trigger the engine to go into Guardian mode.

The after clean up is important. We were "lucky" in that we were on the way to fall haul out, so once Bella was on stands and the drain plug out I could use all the fresh water a wanted to rinse things down.

I'd disconnect the batteries before doing any rinsing, and concur with the WD-40 on electrical terminals. If you are not going to haul the boat, you can use a wet dry vac to remove excess water.

If our experience with the sterndrive configuration of the 8.1 is any indication, the water may not have done any harm. Only your service tech can tell you if there were any bad results from any possible overheating. That being said, Merc is pretty conservative on their fault shut down settings, so any damage may likely be limited to localized issues with the overall health the engine being ok.

Henry