Author Topic: Exhaust Issue? (Read 15755 times)

MikeB · « **on:** July 01, 2013, 10:34:47 PM »

We decided to take the CVX-18 (Mercruiser 228/Chevy 305) out for an evening cruise. It ran really well for about half an hour. On our way back home we decided to blast around at WOT for awhile before noticing a burning rubber/electrical smell. We quickly took it back down to about 2k RPM trying to figure out whether or not the burning smell was coming from us.

We shut off and felt the engine - manifolds were hot but not unusually hot. Temp gauge showed about 120-130. Oil pressure looked alright.

Started back up and noticed the engine didn't have as much power anymore. We trolled back to the dock and could smell a distinct exhaust smell, like a go-kart. Engine was also much louder - like something in the exhaust burned through?

Am I on the right track here?

Rich_V174SS · « **Reply #1 on:** July 01, 2013, 10:53:04 PM »

If you have low water flow from a failing water pump or a blockage someplace in the cooling system your exhaust system could get hot enough to melt the rubber coupling hoses. If your exhaust was getting louder I'd say that's what happened. Your engine compartment could be filling up with carbon monoxide which will choke out your engine causing a drastic loss of power.

carlsoncvx18 · « **Reply #2 on:** July 02, 2013, 12:36:15 AM »

Could it be and engine drive coupler?

Rich_V174SS · « **Reply #3 on:** July 02, 2013, 06:29:38 AM »

That wouldn't affect the sound of the exhaust, but there would be a burning rubber smell. That could, however, be accompanied by a squealing sound and the rpm's would race with the loss of power like that of a spun prop hub.

fireman24mn · « **Reply #4 on:** July 02, 2013, 09:23:29 AM »

White Bear has lots of weeds. I wonder if you had some stuck to the drive for a bit and then before you noticed they came off. Than the temp was back down when you looked at it. Just a thought I get weed on the drive all the time when I am out there. Especally on your end of the lake they seem to be a lot worse. I have a few small pieces of Exhaust hose if you do need it.

MikeB · « **Reply #5 on:** July 02, 2013, 10:55:10 AM »

Thanks guys, I'll take a closer look when I get home tonight. When I had a clogged impeller hold on my Mercury 1150 I cleaned it out with some weed-wacker wire. I'm really confused why my temp gauge didn't budge?

Rich_V174SS · « **Reply #6 on:** July 02, 2013, 11:14:04 AM »

With water in the engine it can take longer for the engine temperature to rise. But if there's no water flowing through the exhaust they can get hot enough to melt things very quickly.

Retro Performance · « **Reply #7 on:** July 02, 2013, 06:47:03 PM »

Do you have any water leakage in the engine compartment? If any bellows burned through (louder) I think you would expect them to leak cooling water (assuming there is flow). on the restart did the engine lose RPM or speed or both?

MikeB · « **Reply #8 on:** July 02, 2013, 09:06:05 PM »

Well I think I found the issue...

About a 1.5" chunk out of the starboard exhaust bellows.

A couple questions I'm still wondering about

- How did this happen? Do I have a blockage in my exhaust risers? Do I need to take them off & clean or just replace them?
- Do I have to pull the engine to replace & diagnose? I'm wondering if I should ask a shop to do this.

I should also mention the impeller was replaced late last year. The stream on the garden hose muffs looked pretty normal.

Rich_V174SS · « **Reply #9 on:** July 02, 2013, 09:09:53 PM »

You don't have to pull the engine out. To change the exhaust coupler boot you have to remove the elbow from the manifold, and from the look of the corrosion at the elbow/manifold joint the elbow could be plugged up with rust and scale. I would pull the elbow just to see what it looks like inside. If it's really bad I wouldn't waste my time with it, just replace it along with the boot and a new gasket. If you do one side you should probably do the other.

Rich_V174SS · « **Reply #10 on:** July 02, 2013, 09:17:35 PM »

Just over a year ago (or two?) my exhaust elbow was all plugged up too. The water outlet holes around the exhaust tube were closed up like clogged arteries and barely passed any water. It was an aftermarket one from GLM. I bought an OEM Mercury replacement used on ebay that was in really clean condition and haven't had a problem since.

Rich_V174SS · « **Reply #11 on:** July 02, 2013, 09:39:36 PM »

Quick question for ya - you say the water pump was replaced late last year, by whom and who's pump parts were used, Mercury or aftermarket?

fireman24mn · « **Reply #12 on:** July 02, 2013, 09:53:04 PM »

Jeff soaked his manifold in muratic acid last year and it cleaned his out and then worked fine. If you need the rubber hoses I be leave I have a set off my 302 manifolds you can have let me know of you want them

carlsoncvx18 · « **Reply #13 on:** July 02, 2013, 10:40:57 PM »

I replaced it with true blue Mercrusier parts.

MikeB · « **Reply #14 on:** July 02, 2013, 11:16:22 PM »

Quote from: carlsoncvx18 on July 02, 2013, 10:40:57 PM

I replaced it with true blue Mercrusier parts.

From the man himself... Thanks again Jeff! My feeling is that the impeller was not related to the problem.

Shawn - Thanks, I'll let you know if I'm in need of a replacement. I may end up replacing both if I take off both elbows.

Rich - Solid advice! I appreciate your insight. I'll take some more pictures once I have the elbows off.

Anyone know where I can pickup muratic acid in the Twin Cities? Do I have to order from a chemical supplier?

carlsoncvx18 · « **Reply #15 on:** July 02, 2013, 11:23:44 PM »

Menards,Home Depot

MikeB · « **Reply #16 on:** July 04, 2013, 11:31:14 AM »

Picked up 2 gallons of muriatric acid earlier today and now I'm stuck getting the elbows off. I have the 4 bolts on the top removed and the metal clamps to the bellows off. Thing doesn't want to move.

I doused it in PB blaster and I'm gonna wait awhile. Are there any other tricks to getting this off?

MikeB · « **Reply #17 on:** July 04, 2013, 12:53:12 PM »

Well after several taps from a rubber mallet back and forth I managed to break free.

At first glance the corrosion doesn't seem all that bad:

Either way, she's going to take an acid bath and get thoroughly cleaned with a coat hanger. The exhust bellows is also going to be replaced. Anything else I should do while it's off?

Rich_V174SS · « **Reply #18 on:** July 04, 2013, 01:42:35 PM »

You should also replace the elbow gasket with the same style as the one on there. Try this: put your garden hose up to the pipe fitting and turn on the water to see how well the water flows through the elbow. If it pressurizes and spits back at you then it's too clogged up. Water should flow through it freely.

MikeB · « **Reply #19 on:** July 04, 2013, 03:12:33 PM »

Tried the garden hose and water did seem to flow freely through. Should I clean with muriatric acid anyway since it's off? Not sure if it's going to strip the paint - I don't want to do more damage than good...

A couple other thoughts...

- We did have the thermostat housing apart last weekend. Is it possible something didn't go back together right and cool water isn't reaching the exhuast? The hoses are in the same spots as always.

- When we bought the boat it was missing the exhaust boot (by the outdrive). I was told you didn't really need one - could that have anything to do with the exhaust running too hot?