Author Topic: Exhaust Issue? (Read 15720 times)

Rich_V174SS · « **Reply #20 on:** July 04, 2013, 03:26:03 PM »

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- 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?

That's a possibility. If it wasn't assembled right the cold water bypass might be blocked off. There should always be water flowing through the bypass whether the thermostat is open or not. The problem could potentially be the thermostat housing itself if it's rusted and plugged up.

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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?

No, that wouldn't matter because the problem is occurring before the exhaust boot.

MikeB · « **Reply #21 on:** July 04, 2013, 04:18:30 PM »

Jeez, I may have done something dumb when reconnecting the thermostat housing...

Here's how I think the hoses are supposed to look:

Here's how we put it back together:

Looks to me like the 2 hoses on each side of the housing are on the wrong way. Is that my problem?

OleRed · « **Reply #22 on:** July 04, 2013, 06:12:11 PM »

yes, the top port goes to the riser, bottom port to the front of the log

MikeB · « **Reply #23 on:** July 04, 2013, 10:51:21 PM »

Just got back from putting around at 6mph to watch some fireworks. Ran the engine for about 2, five minute intervals with a half hour break in between. Never went above 1500 RPM.

Starboard side of engine - still very hot. Manifold felt normal, but elbow and bellows still too hot to touch. It's pretty obvious why one side burned and the other was fine. Even the both hoses running to the thermostat housing felt warmer than the port side.

Port side - felt fine. Manifold, elbow, and bellows felt as cool as I think they should.

I'm not sure why the starboard side is running so hot. I'm thinking I may take it in to a better mechanic than myself.

Rosscoe · « **Reply #24 on:** July 05, 2013, 08:46:19 AM »

Did you pull both risers and flush out? If you're going to do one, you might as well do both. Hose all hooked up the same, starboard and port now?

Rosscoe · « **Reply #25 on:** July 05, 2013, 08:48:56 AM »

Quote from: MikeB 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...

It shouldn't strip the paint. I was at Jeff's when he did his and the crud just came out. Outside had no damage. Soak them in a bucket for 10 minutes or so. May be too late as it sounds like its back together.

MikeB · « **Reply #26 on:** July 05, 2013, 09:22:25 AM »

Quote from: Rosscoe on July 05, 2013, 08:48:56 AM

Quote from: MikeB 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...

It shouldn't strip the paint. I was at Jeff's when he did his and the crud just came out. Outside had no damage. Soak them in a bucket for 10 minutes or so. May be too late as it sounds like its back together.

Yep, I let both risers soak for about an hour. There was a lot of gunk that came out - the acid turned pitch black. Starboard side still feels really hot. The bellows that I replaced I couldn't even touch after running for a few minutes.

Rosscoe · « **Reply #27 on:** July 05, 2013, 09:49:37 AM »

Did you pull the thermostat housing apart too? I guess it doesn't make sense that one side would be hot and the other cool if the thermostat were installed upside down.
Is it the same with the manifolds? One hot and one not? Risers should be warm but not too hot to touch. Thats how Red said they should be when I was plumbing mine.

scott r bishop · « **Reply #28 on:** July 05, 2013, 09:53:45 AM »

One thing I would add here is that we are getting a steady stream of warm water out of the "pisser" hole in the outdrive when running on the hose - am I correct in my thinking that this indicates there is not a significant blockage through the cooling system? The temp sensor never goes above about 110-120, and we did take the thermostat housing apart and boiled the thermostat to make sure that it popped open as I think it should.

Jason · « **Reply #29 on:** July 05, 2013, 09:54:30 AM »

Sure you got all the hoses hooked up right?

MikeB · « **Reply #30 on:** July 05, 2013, 10:09:34 AM »

Quote from: Rosscoe on July 05, 2013, 09:49:37 AM

Did you pull the thermostat housing apart too? I guess it doesn't make sense that one side would be hot and the other cool if the thermostat were installed upside down.
Is it the same with the manifolds? One hot and one not? Risers should be warm but not too hot to touch. Thats how Red said they should be when I was plumbing mine.

Thermostat housing came apart last weekend. The port side riser is warm but starboard side is quite hot. Manifolds were both pretty cool - I could keep my hand on both without burning it.

Hoses should be hooked up correctly now too.

Rosscoe · « **Reply #31 on:** July 05, 2013, 10:16:48 AM »

I imagine you looked at the inside of the hoses for stuff? Maybe a long shot but how about swapping port side hose to starboard and vise versa. No kinks at all?

MikeB · « **Reply #32 on:** July 05, 2013, 12:27:59 PM »

I'll take another look at the hoses tonight.

I spoke with Hannay's and they can't get it in until July 18th! The guy said he thought there was a clog in the manifold or riser. Really hope I can find another fix before then...

MikeB · « **Reply #33 on:** July 05, 2013, 12:43:09 PM »

Looking over some of the pictures I took yesterday I had another idea. According to the manual each of the elbows should have a metal spacer in between the manifold & elbow (gasket - spacer - gasket). When I took the elbows off yesterday, I realized that the port side elbow didn't have a spacer, only a single gasket.

Here's a picture of the riser without the gasket & spacer on:

Here's a picture of what it looks like with the metal spacer on:

Notice how the "slits" on the side of the square hole are covered once the spacer gets put on? Is that restricting water flow? Maybe somebody used the wrong type of spacer? The port side that runs normally didn't have a spacer, and didn't have those holes covered.

OleRed · « **Reply #34 on:** July 05, 2013, 01:38:11 PM »

the purpose of the spacer is to restrict the constant flow of raw water from entering the exhaust log so the risers will stay cool until the thermostat opens, water flows through other ports mainly after the thermostat opens.

Hey ! wait a minute, on a second look, there is no ports in that spacer to allow water ftom the log to the riser other than the restricor hole, that has got to be the wrong spacer, it should have two more ports, on the sides, but it does need that back port restricted.

75starflight · « **Reply #35 on:** July 05, 2013, 01:45:47 PM »

I would say that your spacer is the cause of the heat with the riser. Looks like it is plugged to me.

MikeB · « **Reply #36 on:** July 05, 2013, 01:57:56 PM »

Quote from: 75starflite on July 05, 2013, 01:45:47 PM

I would say that your spacer is the cause of the heat with the riser. Looks like it is plugged to me.

The spacer doesn't have any holes in it - just a solid piece of metal with a gasket on each side (like this):

The port side had a single gasket more like this (no spacer):

The diagram I looked at had a spacer on each manifold, but the only one staying cool is the one without the spacer. Not sure how it's supposed to be...

MikeB · « **Reply #37 on:** July 05, 2013, 01:59:19 PM »

Quote from: OleRed on July 05, 2013, 01:38:11 PM

the purpose of the spacer is to restrict the constant flow of raw water from entering the exhaust log so the risers will stay cool until the thermostat opens, water flows through other ports mainly after the thermostat opens.

Hey ! wait a minute, on a second look, there is no ports in that spacer to allow water ftom the log to the riser other than the restricor hole, that has got to be the wrong spacer, it should have two more ports, on the sides, but it does need that back port restricted.

Thanks Red! I'll look into this over the weekend.

MikeB · « **Reply #38 on:** July 05, 2013, 03:10:04 PM »

Looking online I'm having a hard time finding a block-off plate for a Mercruiser with log style manifold. I can only find center-rise. Sierra-Marine seems to think I need to same block-off plate (without holes) that I'm using now:

Also, the Merc Service manual I am reading shows the same thing.

Would the other (port) side NOT having a block-off plate affect the starboard side? If the water follows the path of least resistance maybe the water is favoring the port side?

Glastronjohn18 · « **Reply #39 on:** July 05, 2013, 04:22:21 PM »

Mike, check "fig. A" shown in your merc manual, spacer with the vent hole. The notes say that spacer is for engines mounted level, such as yours.