manafold and riser question.

smcpest · Jan 7, 2009

Sorry to make this long but I want to go through the details.
I took my boat, with mercrusier 5.0, out to the lake i had just replaced all the belts and hoses on it. After about 15 min. of running i smelled burning checked temp. about 160. I cut motor opened it up right side manifold extremely hot melted rubber boot at bottom. I take it home pull off risers and manifold, water ports extremely clogged so I clean them out put on new gaskets. I haven't replaced rubber boot yet, but started up and water was coming from exhaust.

Is this normal for water to be coming from exhaust or does the risers and manifolds need to be change?

Thanks for any help.

Fishermark · Jan 7, 2009

Re: manafold and riser question.

smcpest said:
...I take it home pull off risers and manifold, water ports extremely clogged so I clean them out put on new gaskets. I haven't replaced rubber boot yet, but started up and water was coming from exhaust.

Is this normal for water to be coming from exhaust or does the risers and manifolds need to be change?

Thanks for any help.

Yes, it is normal for water to come out the exhaust. That keeps the rubber from burning.

Having said that, you cannot simply clean out the passages in the manifolds and risers and expect them to stay open. It is time for replacement.

You also need to check your water pump in the outdrive - I'm sure you melted some parts there as well since the water flow was blocked.

bpmcl00 · Jan 7, 2009

Re: manafold and riser question.

What year is your boat?

9533Zero · Jan 7, 2009

Re: manafold and riser question.

Fishermark said:
... you cannot simply clean out the passages in the manifolds and risers and expect them to stay open. It is time for replacement.

Is it really not possible to clean out the passages? What about a dip in Muratic acid? Replace just because they are dirty and clogged? I'm looking at the same situation right now on my 3.0. Thanks!

Steve

DJ · Jan 7, 2009

Re: manafold and riser question.

If they are that bad, they're thin. Replace them.

You DO NOT want one to fail.

arty007 · Jan 7, 2009

Re: manafold and riser question.

i have the same dilema buy or try to clean

9533Zero · Jan 7, 2009

Re: manafold and riser question.

I'm with ya DJ. I guess its hard to say for sure though without seeing the part.

Don S · Jan 7, 2009

Re: manafold and riser question.

arty007 said:
i have the same dilema buy or try to clean

What's the dilema? This is a one answer fits all answer. You get the same answer as 9533Zero.
Manifolds and risers should NEVER be cleaned if they are plugged up. I don't care if it's a 4 cylinder or a 7.4 V8, Mercruiser, OMC, or Volvo. They get replaced.

smcpest · Jan 12, 2009

Re: manafold and riser question.

You also need to check your water pump in the outdrive - I'm sure you melted some parts there as well since the water flow was blocked.

Thanks to all who answered.
Only one side of the manifold got hot so I still had water flow to other side. (1988 mercrusier 5.0) Do you still think the impeller in the foot would be damaged? I just replaced it a short time ago, hate to do it again if not needed.

Thanks Again

chiefalen · Jan 12, 2009

Re: manafold and riser question.

I'm not one for checking impellers, usually go thru all the trouble to pull it, than i replace it.

Some look ok, but cheap insurance that your gonna have good water going to the motor. And it's the one thing you can't mess with while on the water, most any other problem with the cooling can be dealt with in the engine bay.

Unless something blocks the water inlet in the lower end ,like a plastick bag getting wrapped around the lower. That you can just get off the lower bye raising the drive.

Bondo · Jan 12, 2009

Re: manafold and riser question.

Only one side of the manifold got hot so I still had water flow to other side. (1988 mercrusier 5.0) Do you still think the impeller in the foot would be damaged? I just replaced it a short time ago, hate to do it again if not needed.

Ayuh,... It's Maybe$20. in Parts,.. Do you want to take a Chance,.. Go Ahead, Roll the Dice...

Did you pull the Other Manifold,+ Riser to see how Bad that side is,..??
Did you Replace Either of them,..??

chiefalen · Jan 12, 2009

Re: manafold and riser question.

You know i took it for granted that he knew enough to yank the other side to look at them. Didn't think i needed to ask.

Bet he's gonna be looking for a half a grand special .

smcpest · Jan 13, 2009

Re: manafold and riser question.

To all that didn't understand the second Question on my post.

First off I did replace both manifolds and risers(Both Sides) My question was asking about what FISHERMARK said, I should check the water pump in the outdrive, I didn't understand how one clogged manifold would cause damage to this as there was still water flow through the other manifold. I just replaced waterpumpin the foot a month or so ago.

I admit I don't know everything when it comes to these motors, but I'm not an IDIOT. If someone recommends I do something I want to understand why I'm doing it. Not trying to be cheep just trying to understand.

Don S · Jan 13, 2009

Re: manafold and riser question.

There is no way for any of us to know if your pump is ok or not. We didn't get to see the water flow or anything else. The only thing you could hope for from us is a WAG. (Wild Guess)
You have 2 choices really. Pull the drive apart and inspect the pump housing and impeller, or take the boat out and run it and see what happens. It's your choice. Read my signature (The blue part)

chiefalen · Jan 14, 2009

Re: manafold and riser question.

I understand your frustration, however to be safe, and insure a good water supply to the engine, if it were my boat, i would replace the impeller, and if the housing was compromised that as well.

The melting of the exhaust hose was the worry, in my mind, that of course is new also ?

New risers, new manifolds, new impeller, your good to go for at least 3-5 years.

T-stat good ?

Have fun and good luck !

Cptkid570 · Jan 14, 2009

Re: manafold and riser question.

I understand what he is saying.. If he never lost water flow through the impellor and the water in the impellor never got hot, then why would it be damaged?

However, I do understand everyone's "better safe than sorry" approach.

You can run it in the driveway and see if you are getting waterflow, check the risors and make sure they are staying cool enough... then water test it and keep and eye on the temp... Just my opinion. If the engine never got above 160, I'm guessing that one side clogged, but the cooling process still worked, but the water drained though the path of least resistance and didn't cool the side where the rubber failed.

Just my opinion.. I just see where he is coming from.

Fishermark · Jan 15, 2009

Re: manafold and riser question.

I've been out of town for a few days so I am only now getting a chance to check on a few posts. I still suggest pulling the lower unit off and looking. It is not the impeller that I would be worried about, but the housing itself. I've seen where the hot exhaust gas can melt and/or warp the housing. Like Don mentioned above, it would only be a guess for anyone - including yourself.

I wouldn't suggest going out and buying a new pump - YET. Simply pull the lower unit off and take a quick look. It will be pretty obvious if you do have damage or not.

By the way... I'm speaking from experience:

chiefalen · Jan 15, 2009

Re: manafold and riser question.

Maybe he will listen now.

Pic is worth a thousand words.

smcpest · Jan 28, 2009

Re: manafold and riser question.

Thanks to Cptkid570 and Fishermark I'm glad you explained how the damage can occur. I will be pulling the lower unit this weekend to check it out.

To Chiefalen sorry for trying to understand why and how things go wrong and not just following orders blindly.

chiefalen · Jan 28, 2009

Re: manafold and riser question.

An order is what you do at Friday's or any diner, want a order of fries with that.

Here it's advice thats freely given, and it's up to the poster to accept or reject the advice.

Glad you listened anyway, cause i would hate to see YOUR boat with major damage for want of a 20 dollar part.

Your welcome.

Good luck !

manafold and riser question.

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