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mjdavis
06-26-2012, 02:09 PM
I've got a 1989 boat and a well experienced marine mechanic suggested that it might be time to change out my exhaust manifolds and risers. He said there was evidence that the gaskets between the manifold and risers were leaking and that means the internals are wearing out and are probably corroded. He said if I don't do it then eventually water could work its way back through the exhaust valves and into the cyliners which would cause a catastrophic failure of the engine.

Question, does his anaylsis make sense? It sounds a little reasonable but I also know that he would stand to gain if I asked him to replace the parts.

If a replacement is advisable, is it a big job? To me it doesn't look like it (assuming the new manifolds and risers were available!).

Finally, would it be possible to resuse the manifolds and risers after some refurbishment?

Thanks so much!

mayo93prostar
06-26-2012, 02:19 PM
just because the gaskets leak does not mean the manifolds and risers are bad. I still have the originals on my 93 prostar and it has been run in brackish (salty) water all of its life but with flushing after every use. the best way to tell the condition is to take them apart and replace the gaskets and bolts, after inspection. You can get a kit at www.skidim.com depending upon what marinization you have. It is not a big job, just they are a little heavy. I have replaced the gaskets on mine and cleaned out the water jackets on mine twice in the last 3 years.

Lumbergh
06-26-2012, 02:45 PM
Easy job.

Get the manifold kit at skidim, riser kit there too (though I prefer the Indmar kit available from your local boat shop or online):

http://store.inboardonline.com/iwwidb.pvx?;multi_item_submit

http://www.skidim.com/prodinfo.asp?number=49-2004

Takes a few hours but simple work.

mjdavis
06-26-2012, 02:48 PM
Perfect, thanks Lumbergh and mayo93prostar. That's just what I hoped to hear!

mjdavis
06-26-2012, 09:00 PM
One more question, where can I find the torque specs for the exhaust system? Or is this unecessary since the manifolds and risers are not load bearing?

Cloaked
06-26-2012, 09:17 PM
One more question, where can I find the torque specs for the exhaust system? Or is this unecessary since the manifolds and risers are not load bearing?Snug tight is fine. Use anti-sieze on the threads. While you're there, replace the exhaust hoses too. They go bad when they look great on the outside. Click on the link in my signature line for an example.

Use some 80 or 120 grit sand paper to clean the old gasket material from the mating surfaces.

You may need to grind a side of a box wrench to get it to fit inside of the riser mold to get on the hex head, or cut an allen wrench off a bit for the same similar fit.

I doubt your risers are bad just becaues a gasket looks like it might leak. Makes me laugh a little. Those things will go forever in fresh water unless you do not drain in the winter. Then you'll see other issues.

.

Lumbergh
06-27-2012, 12:14 PM
Snug tight is fine. Use anti-sieze on the threads. While you're there, replace the exhaust hoses too. They go bad when they look great on the outside. Click on the link in my signature line for an example.

Use some 80 or 120 grit sand paper to clean the old gasket material from the mating surfaces.

You may need to grind a side of a box wrench to get it to fit inside of the riser mold to get on the hex head, or cut an allen wrench off a bit for the same similar fit.

I doubt your risers are bad just because a gasket looks like it might leak. Makes me laugh a little. Those things will go forever in fresh water unless you do not drain in the winter. Then you'll see other issues.

.

This pretty much sums it up. Better to over maintain, than the other way around. The parts to do the basics are pretty cheap IMHO.

mikeg205
06-27-2012, 02:03 PM
just because the gaskets leak does not mean the manifolds and risers are bad. I still have the originals on my 93 prostar and it has been run in brackish (salty) water all of its life but with flushing after every use. the best way to tell the condition is to take them apart and replace the gaskets and bolts, after inspection. You can get a kit at www.skidim.com depending upon what marinization you have. It is not a big job, just they are a little heavy. I have replaced the gaskets on mine and cleaned out the water jackets on mine twice in the last 3 years.

How did you clean out the water jackets? Do you think this would be a good thing to do if you have the manifolds and risers off?

Just did my risers so I am good for a few years, unless Cloaked's hose picture haunts my dreams.... :D

mayo93prostar
06-27-2012, 03:05 PM
I used a drill bit to "mill" the water jackets, where the risers meet the manifold, out a little with a electrical drill free hand. they were a little narrowed down with corrosion. You only need to do this if they are not full open. A key area to look at is at the round exit of the riser to be sure their is space between the inner ring and outside casing for the water to flow. My neighbor's risers were almost totally closed off causing overtemperature and he bought new ones that I put on for him.

Panda Cub
06-27-2012, 04:03 PM
My .02 would be replace the gaskets, it's cheap and easy. Also I agree with replacing the hoses, I did that this spring as well. Here is the end product!

80821

Take good care of your motor, and it will take care of you! On second thought its a boat, so it is a money pit no matter what!

Lumbergh
06-27-2012, 06:55 PM
! On second thought its a boat, so it is a money pit no matter what!

Yes, there is an entire thread about that...BOAT.

Good times...

mikeg205
06-27-2012, 07:53 PM
My .02 would be replace the gaskets, it's cheap and easy. Also I agree with replacing the hoses, I did that this spring as well. Here is the end product!

80821

Take good care of your motor, and it will take care of you! On second thought its a boat, so it is a money pit no matter what!

Hey is that someone praying to the boat-god in the lower left hand corner of the picture??? :rolleyes:

Panda Cub
06-27-2012, 08:49 PM
Hey is that someone praying to the boat-god in the lower left hand corner of the picture??? :rolleyes:


Grabbing a beer, sorta praying to the boat gods.

Tom190driver
07-07-2012, 09:37 PM
Do you have to take off the risers if all i need to do is replace the exhaust hoses,risers are new this year. thanks

mikeg205
07-08-2012, 01:05 PM
IMO yes...don't know how you would get hoses of with out taking risers off.

Tom190driver
07-08-2012, 01:16 PM
Thanks mgorczaki i should have changed the hoses when i did the new risers. LIVE AN LEARN

MasterKraftS&S
07-08-2012, 02:14 PM
I think my mechanic prefers to put things off till they break(proly works out BETTER - for him) I noticed THIS when I was prepping the boat this year. Does the MC Guide Book ever mention DUCT TAPE on the exhaust? When asked, he said they were all clear inside and didn't need replacing - he did have the motor out this spring. What say you?

mikeg205
07-08-2012, 02:22 PM
Thanks mgorczaki i should have changed the hoses when i did the new risers. LIVE AN LEARN

Thinking more...you might be able to cut them off if replacing... it's the removing which is difficult if you don't want to cut....re-installing new should be pretty easy when new...

Cloaked
07-08-2012, 02:23 PM
...my mechanic prefers .......DUCT TAPE..... ......... he said they were all clear inside and didn't need replacing - ..........

What say you?
........................... LOL

mikeg205
07-08-2012, 02:28 PM
I think my mechanic prefers to put things off till they break(proly works out BETTER - for him) I noticed THIS when I was prepping the boat this year. Does the MC Guide Book ever mention DUCT TAPE on the exhaust? When asked, he said they were all clear inside and didn't need replacing - he did have the motor out this spring. What say you?

Not my MC book...lol

There's a picture in TT showing someone who replaced the mufflers with PVC. However, I see baffles in my silentmasters...

Hey it's duct tape...good enough for Apollo 13 -should be good enough for MC...lol... personally I would re-glass if possible for small leaks...

why was it taped?

MasterKraftS&S
07-08-2012, 03:00 PM
Not my MC book...lol

Hey it's duct tape...good enough for Apollo 13 -should be good enough for MC...lol... personally I would re-glass if possible for small leaks...

why was it taped?

Not Sure WHY/WHEN - Rarely lift up the skirt myself. Looks like a project to add to the list for the off season.