'97 370 DA Telltale Exhaust Problem

[daveduchaj]

My starboard raw water pump failed and the hot exhaust apparently damaged the bypass for the underwater exhaust. At idle, I see little or no water at the telltale and see exhaust bubbling up under the starboard transom. The engine is now running at normal operating temps with no other issues. Any idea where the bypass is and what the part number would be? The Sea Ray parts manual does not diagram the components and the descriptions are vague.

Thanks!

 

[fc3]

Far as I know, it's inside the horizontal log exhaust collector. It's just a big tube with a smaller tube inserted for what I think you are calling the bypass and a vertical tube for the main passage to below the hull. I don't believe there are any moving parts.

Never bothered to look to see what's inside that collector.

 

[Alegria]

Sorry I can't add any more constructive info to the thread only to say I have a similar issue on my port exhaust. There was no water flow at time of survey, under water exhaust was fine and the temps were perfect. MM assumed it was a blockage. They took out the port mufller and found it was melted and was most likely constricting the flow. This is the muffler mounted up on the stern. They removed it and replaced it with a new one. There is water flow now but its weak. They did replace the fuel/water pump housing with new one, that I did see, so I am assuming, incorrectly?, that they may not have replaced the impeller, but I think that is unlikely.

The only other thing is that log muffler that the exhausts run into, but I don't know what that looks like on the inside to suggest where a blockage might be.

I am wondering on mine if the PO has an impeller failure and there are parts blocking or binding up water flow early on in the process... My temps are fine and my underwater exhaust is similar to the starboard one so right now I am keeping an eye on it. Are there two water pumps? As I have closed cooling on the elbows (2 connections) and am wondering where that pump is mounted, I am betting towards the forward bulkhead under where the expansion tank is located.

FC you should get out your borescope and scope it out and see whats in that log collector... HMMM I could use a new toy.. How much are those scopes?????

Sorry I can't be more helpful...

 

[daveduchaj]

Thanks for the responses. From these I gather that the the stern mounted muffler may be the culprit and that the engine is exhausting through the underwater fitting at idle because the muffler became blocked due to high temps. There was a resinous residue around the telltale exhaust suggesting something may have melted in the (very) brief time that the engine ran w/o raw water cooling.

I did notice an unusual water trickling sound going down the vertical tube immediately after engine shutdown, post repair. That could have been water that would normally have exited out the telltale.

Alegria - I can't imagine them replacing the pump body w/o replacing the impeller. If your engine temps and underwater exhausts are tracking the same then I would bet on blockage from the muffler to the telltale. Broken impeller bits in-line would likely result in higher temps in the port engine. I have replaced disintegrated impellers before but always managed to collect all the broken bits - at least I assume so!

Thanks again for the input.

 

[Alegria]

Alegria - I can't imagine them replacing the pump body w/o replacing the impeller. If your engine temps and underwater exhausts are tracking the same then I would bet on blockage from the muffler to the telltale.

Thanks again for the input.

I agree! They had the muffler out to replace it and checked the outlet of the muffler to the through hull and found no blockage. So I still left wondering why I don't have more flow on the port engine. I cleaned the strainer last weekend and bled some water from the through hull to check that for flow and she was flowing fine. :huh:

 

[fc3]

FC you should get out your borescope and scope it out and see whats in that log collector... HMMM I could use a new toy.. How much are those scopes?????

Fiberoptic borescopes are pretty darned cheap now. I paid $120 for mine from SJ Discount Tools. You can spend a few hundred or even a few grand on these things. But this one works agreeably well. I didn't think of looking inside the log when I had the exhaust system open. Boat is in the water, so can't go in from below and it's not easy to go in the side port since the muffler has baffles. Pulling the exhaust tube off the elbows is a pain in the butt. I think Dave is going to have to get a scope or disassemble the exhaust system and inspect with a mirror and bright light.

I have a spare muffler downstairs. You can still get them right from the manufacturer.

Best regards,
Frank

 

[daveduchaj]

It turns out that the 2.5" elbow on the collector (log) has a tube that extends internally to the bottom of the horizontal pipe. Exhaust gas forces the cooling water up and out through the telltale, producing the visible water discharge. The resin melted, collapsing the tube and hence no water discharge from the telltale. Centek makes the part and is direct shipping - much cheaper and faster than ordering through my local dealer. I called Sea Ray to get the manufacturer's part number...