PDA

View Full Version : Exhaust hose meltdown - AGAIN!!!



cutwater
08-09-2007, 10:33 AM
A little while ago I posted about the hardwall exhaust hoses that ruptured on the Minx. I was suspicious since both went out around the same time, but I thought maybe they had just dry-rotted, so I replaced them with MPI softwall wet exhaust hoses. They were "steaming" and warping slightly right after the engine came up to temp, and within 30 minutes I had melted holes in both hoses.

I am at a loss, because I AM picking up raw water, as I can see it exiting the through-hull exhaust. Also, the engine temp gauge never goes past 150 degrees (fluctuates between 135 and 150 degrees - seems a little low to me?).

I can only think of two things: The engine temp gauge is incorrect and I am actually overheating, or I am not getting as much water through the risers as I should. Any thoughts?

MOP
08-09-2007, 10:55 AM
Do you have stock cast iron, if so I may have a fix!

RickR
08-09-2007, 11:01 AM
Are the manfolds or risers very hot to the touch after a hard run?
What kind of exhaust do you have?

VetteLT193
08-09-2007, 11:04 AM
You run an OMC right?

Maybe your pump is only half working... enough to keep the engine cooled, but not enough to cool the exhaust. I've seen plenty of impellers with missing fins.

I don't have any clue how the OMC engines handle the water pumping though:boggled:

mrfixxall
08-09-2007, 11:05 AM
risers and or manifolds are parcialy plugged( rusted up inside),,then the exhaust melts the rubber exhaust bellow..

cutwater
08-09-2007, 11:50 AM
Yes, stock OMC cast iron. They're the end risers, 1988 350 SBC.

I'm not very familiar yet with OMC either, but they do feel pretty hot to the touch.

I will take the risers off and look for rust as soon as I can. Anything else I should specifically check while I'm at it?

VetteLT193
08-09-2007, 12:28 PM
Yes, stock OMC cast iron. They're the end risers, 1988 350 SBC.
I'm not very familiar yet with OMC either, but they do feel pretty hot to the touch.
I will take the risers off and look for rust as soon as I can. Anything else I should specifically check while I'm at it?


If you haven't checked the impeller yet, I would at least check it. When I bought my boat I pulled the lower to inspect, change the oil, and do the impeller.

I pre-purchased the impeller and wound up not using it because the one in the boat is perfect... I at least have peace of mind now:)

Hopefully there are OMC instructions here, or on the net, so you can dig into it. It's no big deal on an Alpha, and I doubt OMC is any harder.

RickR
08-09-2007, 01:22 PM
+1 w/Mr Fixall! Riser gaskets available @ NAPA.
I would use Hylomar on the riser/manifild gasket also.

HMMMMM? 20 year old water jackets (exhaust), you start digging around and cleaning them be perpared for a leak :( Probably time for a new set anyway.

cutwater
08-09-2007, 01:37 PM
Okay, so if I've got rust in the riser jackets I'll probably have rust in the exhaust manifolds too, right? Should I take both off?

If I do have rust or debris in there, how should I attempt to clean out the water jackets?

RickR
08-09-2007, 01:48 PM
I am NOT famaliar with your manifolds. Does the riser/manifild joint have bolts or studs?

If the manifold bolts have been on for 19 years there might be an issue getting them off. Especially if the boat has been in salt water.

I would let the water out of the manifold (remove hose) and/or drain plugs, then, remove 4 riser bolts. You might need to break the riser loose with a rubber hammer or block of wood.
Remove riser and inspect.
See if you can remove rust from the riser with air and water hose. I would not use a caustic chemical on a manifold that old :(

Post pics if you can.

gcarter
08-09-2007, 02:21 PM
I had a problem w/my Minx and the Stainless Marine risers and exhaust hose. There was too much down angle on the risers and the top central part of the hoses would burn out.......
It was just bad geometry!!!!!

VetteLT193
08-09-2007, 02:26 PM
I really think it's going to be a much easier to check the water pump first, and it's more likely the cause considering that both exhaust hoses failed at once.

If one went, and continued to be a problem I'd lean towards a problem with the manifolds... even if one went and then shortly after a the 2nd one went I could see, but but both at the same time really points to a water flow issue IMO.

And, the engine temp gauge could easily be wrong, or just misleading.

mrfixxall
08-09-2007, 02:49 PM
Yes, stock OMC cast iron. They're the end risers, 1988 350 SBC.
I'm not very familiar yet with OMC either, but they do feel pretty hot to the touch.
I will take the risers off and look for rust as soon as I can. Anything else I should specifically check while I'm at it?


IMpeller is easy to check,,remove the back cover on the drive...look for a black housing with a little hose attached,remove the 3 bolts and impeller and housing gome off together..

zelatore
08-09-2007, 04:02 PM
+2 Mrfixall on the risers/manifolds. If those are the orriginals, you've got WAAAAAY more life out of them than ever expected :eek!:

Sure, check the impellor, but I'm betting the rust monster has done in the risers/manifolds

MOP
08-09-2007, 05:29 PM
I don't know but it seems like a horse race!

1. engine shows good temp
2. he states good water flow out of the exhaust

Neither is an indication of a bad pump or bad risers, not saying they are not. But lets do a little normal dio before it is all torn apart, it only takes a few minutes to check the pumps out by the book. I have a hunch the pump is doing just fine and able to force water through what is left of the passages. Temp problem checks 1-O-1: This must be done on the water to prove the pumps ability! Remove hose coming from the transom and insert it into a bucket, start the engine let it run for 1 minute. A bottom shifter OMC will put about 2-1/2 to 3 quarts of water in the bucket at idle in a minutes time, if it passes then go on to the risers. To be good at this crap you need to do things in steps!

VetteLT193
08-14-2007, 12:07 PM
cutwater, any updates?

cutwater
08-14-2007, 01:23 PM
cutwater, any updates?

Hey Vette... been a crazy week. *Hopefully* tonight I will be able to go check the flow rate from the impeller itself, then the flow out of the water pump. After that I guess I will knock off the risers and inspect the water jackets.

Anyone know where I can get a reasonably priced set of exhaust manifolds/risers? Lenny has a set for sale but they have the Vortec ports, and I think mine is non-Vortec ('88 Merc 350 block). I'm not making big power, and I just need something basic for a few years until I upgrade the power.

Thanks,
John

VetteLT193
08-14-2007, 01:38 PM
Hey Vette... been a crazy week. *Hopefully* tonight I will be able to go check the flow rate from the impeller itself, then the flow out of the water pump. After that I guess I will knock off the risers and inspect the water jackets.

Anyone know where I can get a reasonably priced set of exhaust manifolds/risers? Lenny has a set for sale but they have the Vortec ports, and I think mine is non-Vortec ('88 Merc 350 block). I'm not making big power, and I just need something basic for a few years until I upgrade the power.

Thanks,
John

eBay has some pretty cheap manifolds. there are even OMC ones on there, not sure if they match yours or not though.

MOP
08-14-2007, 02:35 PM
The exhaust ports are the same, the Vortec intake passages are different.

cutwater
08-14-2007, 02:47 PM
The exhaust ports are the same, the Vortec intake passages are different.

Hey MOP -

Sorry I'm a bit uninformed about this subject. Lenny said his (the late model red Volvo manifolds) have 4 bolts.
http://www.donzi.net/forums/showthread.php?t=49660

So will these work in my application? I was assuming that mine had 6 bolts and didn't think they would be interchangeable.

gold-n-rod
08-14-2007, 05:25 PM
Anyone know where I can get a reasonably priced set of exhaust manifolds/risers? Lenny has a set for sale but they have the Vortec ports, and I think mine is non-Vortec ('88 Merc 350 block). I'm not making big power, and I just need something basic for a few years until I upgrade the power.

Thanks,
John

I think the shipping will bust your balls. I have a set off my 5.0, but the damn things prolly weigh 150# for the pair.

Buying them locally is probably your best bet.

MOP
08-14-2007, 06:47 PM
Hey MOP -

Sorry I'm a bit uninformed about this subject. Lenny said his (the late model red Volvo manifolds) have 4 bolts.
http://www.donzi.net/forums/showthread.php?t=49660

So will these work in my application? I was assuming that mine had 6 bolts and didn't think they would be interchangeable.

Yes they will work, ask Lenny to get the weight for you and check the price with FedX ground. They are cheaper then UPS or the PO for shipping heavy items. My BravoX came a long way for $80.

Phil

MOP
08-14-2007, 07:54 PM
Wait until you drain the manifolds and get the risers off, you may find they are not bad but plugged from some scale.

Phil

cutwater
08-16-2007, 03:15 PM
1. MOP - did you mean gallons instead of quarts? The raw water feed directly from the transom filled up a one-gallon jug in about 15 to 20 seconds = 3 or 4 gallons/minute.
2. RickR - Last night, the manifolds were only mildly warm to the touch (seemed very normal) after idling for a while, but I didn't run it hard.
3. Starboard exhaust (exhaust gas and manifold itself) runs slightly hotter than port :confused:, but I know for sure that the port exhaust hose ruptured about 10 minutes before the starboard.

Last night, the hoses were still hot but didn't seem to "steam" and warp like last time. If this is an intermittent problem, I would think it's the impeller starting to go bad? I will probably replace the impeller and thermostat this week regardless. When I replace the burned hoses, I will inspect the manifolds and risers.

I have attached pictures of the burned hoses and videos of the boat (idling and revved - Sorry it was pretty dark by the time I took the video).

Video 1 - Idling : http://www.youtube.com/watch?v=AlknqRKki2E
Video 2 - Revved : http://www.youtube.com/watch?v=TXizQZjjqQs

The high-res videos are also attached - easier to see, but BIG (6 MB).

John

cutwater
08-16-2007, 03:22 PM
By the way, in Tennessee duct tape will fix anything... for a few minutes! It was enough to get me back to the dock. The exhaust in the bilge was starving the engine for air. I guess it ran so rich when the hole opened up that I got black soot all over everything in the bilge :(

drew0982
08-16-2007, 03:27 PM
I don't know anything about inboards, but what I don't understand is why you'd use hose instead of pipe for exhaust? :confused:

zelatore
08-16-2007, 06:45 PM
I don't know anything about inboards, but what I don't understand is why you'd use hose instead of pipe for exhaust? :confused:

One word: flexibility

Look at any inboard or I/O setup and you can see why you need it. The engines will move on their mounts realitive to the transom somewhat unless you're running solid mounts (maybe in a race-only situation, but nothing I konw of stock). Got to have some give in the system somewhere or it's going to make it's own. :)

gcarter
08-16-2007, 07:01 PM
I haven't read all this, but several gallons of muriatic acid in a plastic bucket will completely remove scale from any iron pieces soaked in it. Doesn't take long either.

MOP
08-16-2007, 07:24 PM
Ok the water pump is well above the acceptable rate! Pull the risers they are plugged, snap a pic of the mating surface the thickness of the casting determines need for replacement or cleaning.

Phil

MOP
08-16-2007, 07:26 PM
Hmmm did not look a pics first time around! Original OMC's even in fresh water it is probably time to chuck them.

Phil

drew0982
08-16-2007, 09:32 PM
One word: flexibility
Look at any inboard or I/O setup and you can see why you need it. The engines will move on their mounts realitive to the transom somewhat unless you're running solid mounts (maybe in a race-only situation, but nothing I konw of stock). Got to have some give in the system somewhere or it's going to make it's own. :)



I guess we're so used to making everything rock solid down here because of seas we'd probably use solid mounts anyway:) Thanks for the info though:cool:

98shovel
08-16-2007, 10:08 PM
from the amount of water comming out in the vid i dont see a problem with water flow
i used a 4" stainless tube with short rubber pieces on both ends that way the rubber only is on the ends and doesn't see direct heat
then went to tube headers ond dont have to worry about it

VetteLT193
08-17-2007, 07:46 AM
Are you getting water spraying out of the holes in the melted hoses?

cutwater
08-21-2007, 02:55 PM
I pulled the impeller this wknd and it looks like 2 of the fins were half missing. Also, the "sleeve" or whatever you call it that compresses the impeller blades was turned so that about 15% of the water flow was cut off. I am not sure that this is the entire problem since I was getting good water flow at idle, but it could explain things if this is more of an intermittent problem. I will inspect the risers this wknd.

What temperature should the exhaust hoses be rated at?

mrfixxall
08-21-2007, 03:40 PM
I pulled the impeller this wknd and it looks like 2 of the fins were half missing. Also, the "sleeve" or whatever you call it that compresses the impeller blades was turned so that about 15% of the water flow was cut off. I am not sure that this is the entire problem since I was getting good water flow at idle, but it could explain things if this is more of an intermittent problem. I will inspect the risers this wknd.
What temperature should the exhaust hoses be rated at?


Replace the housing to,it will only spin again under higher rpm's

cutwater
08-21-2007, 03:52 PM
I bought a new sleeve, and I plan on using a 2part epoxy to secure it in the housing. I don't think there's any circumstance where you would want that sleeve to shut off water flow, right? It relies only on a snug fit (as it is) to keep it from spinning... seems like a poor design.

mrfixxall
08-21-2007, 04:01 PM
I bought a new sleeve, and I plan on using a 2part epoxy to secure it in the housing. I don't think there's any circumstance where you would want that sleeve to shut off water flow, right? It relies only on a snug fit (as it is) to keep it from spinning... seems like a poor design.

Ruff up both pieces to give the epoxy somthing to stick too:wink:

VetteLT193
08-27-2007, 08:36 AM
I bought a new sleeve, and I plan on using a 2part epoxy to secure it in the housing. I don't think there's any circumstance where you would want that sleeve to shut off water flow, right? It relies only on a snug fit (as it is) to keep it from spinning... seems like a poor design.

Did the pump come back together ok?
How do the risers look?

I'm curious because I haven't been able to work on or use my Minx:wink:

cutwater
08-27-2007, 09:12 AM
Last night I was able to take the Minx out for the first time since replacing the impeller, sleeve, etc., changing drive oil, hoses (got a free set, so I figured I'd try again) and so on. And I had the same problem, which I kind of expected since the raw water flow looked about the same as before. So now I'm thinking it might be the circulation pump? Basically I'm thinking that the impeller is forcing enough water through to cool the block, but it is shouldering the whole load so it isn't forcing water through hard enough to sufficiently "spray" the hose walls. Take it easy on me if I'm completely misunderstanding something :bonk:

Should I just fill up a bucket and see if the water pump draws it out sufficiently once the thermostat opens up? I'm going to try to get new risers and manifolds too - I need to do this regardless. I looked at the water jackets when I put the hoses on, and yes they had a very thin layer of rust, but it didn't seem too bad. Is any rust too much?

MOP
08-27-2007, 09:18 AM
I would back flush the oil cooler first, a circ pump does not make sense you can take the belt off and it will still cool like a cross over! You need to find the missing rubber from the impeller.

VetteLT193
08-27-2007, 09:47 AM
Last night I was able to take the Minx out for the first time since replacing the impeller, sleeve, etc., changing drive oil, hoses (got a free set, so I figured I'd try again) and so on. And I had the same problem, which I kind of expected since the raw water flow looked about the same as before. So now I'm thinking it might be the circulation pump? Basically I'm thinking that the impeller is forcing enough water through to cool the block, but it is shouldering the whole load so it isn't forcing water through hard enough to sufficiently "spray" the hose walls. Take it easy on me if I'm completely misunderstanding something :bonk:
Should I just fill up a bucket and see if the water pump draws it out sufficiently once the thermostat opens up? I'm going to try to get new risers and manifolds too - I need to do this regardless. I looked at the water jackets when I put the hoses on, and yes they had a very thin layer of rust, but it didn't seem too bad. Is any rust too much?

The risers always rust. It's just a matter of time:( You can run salt-away (or similar) at the end of each flush to help get some of the rust off, and slow down the creation of new rust. Even if you don't run in salt water it will only help.

If the manifolds/risers look ok, it's a really confusing problem. I don't run flappers, which may make the water flow look greater, but your water flow seems better than mine based on the videos.

Speaking of flappers, do they open and close easily? If they are choking down the exhaust I could see a build up of heat to melt the rubber. Even though it's relatively unlikely you might want to just pull them off (assuming they are the basic clamp on style) to eliminate them as a possible problem.

The circulation pump really isn't needed. And generally if it isn't making noise (squeeling) it's going to be ok.

A possible spot for your missing rubber impeller pieces is the T-Stat area. It's probably the smallest opening, and it's easy to get to and check.

cutwater
08-27-2007, 10:02 AM
I would back flush the oil cooler first

Thanks MOP. What's the method for this? Also, besides the manifolds/risers, am I overlooking something else that could be the problem?

maddad
08-27-2007, 10:38 AM
I was having a problem with hot exhaust temps, MOP suggested air leak causing steam pockets. My pump is crank driven so it took a little work to find it(more suction side connections), but you should look at every seal and connection on the raw water side of your pump. A small leak on my sea strainer gave me a ton of grief before it was fixed.

MOP
08-27-2007, 11:05 AM
Follow the hoses from the power steering down to find the cooler, it is almost guaranteed that rubber shards will end up there. you can usually remove the hoses and flush them out with a garden hose. It still may also be the risers!!!

Phil