Hot Exhaust Risers.

[GunHoInc]

I just got a new 5.7 put in my boat. And the shop says my Risers are hotter than they should be and are working on the issue now. So I'm just double checking what the issue may be.

They replaced the impeller already and the issue is still there. The motor still has the old water pump on it though. (Should have bought a new one) Is it possibly the risers are clogged trapping the water, or do you think the old water pump is toast. The engine doesn't over heat, as it's running well below 170.

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[Don S]

Re: Hot Exhaust Risers.

What are we working on here, Mercruiser, OMC, Volvo, and what would be the year?

 

[GunHoInc]

Re: Hot Exhaust Risers.

Whoops.

1986 Sea Ray 210 CC
Brand New Mercruiser 5.7 ltr.
Alpha 1 Gen 1

Also the old impeller was fine but was replaced anyways.

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[Don S]

Re: Hot Exhaust Risers.

Raw water cooling or closed cooling system installed.
You used the old manifolds and risers on a brand new engine
Why did you replace the engine?

 

[swordfish25]

Re: Hot Exhaust Risers.

Check the water hose that goes from the drive to the gimbal housing,these can kink .Check the thermostat for temp. I use 140 deg.

 

[GunHoInc]

Re: Hot Exhaust Risers.

This is a raw water system.

I just bought the boat and it had a junkyard 305 in it with a bad bearring. So I had it pulled and replaced with a new 350. But yeah, I used the old exhaust manifolds and risers as they looked fairly good.

Not sure what temp. the thermostat is that's in it. I'll ask tomarrow.

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[Don S]

Re: Hot Exhaust Risers.

yeah, I used the old exhaust manifolds and risers as they looked fairly good.

Old manifolds and risers kill more marine engines than anything else (besides freeze damage).
Look at the outlet openings and passages from the risers. are they wide open?
Then you have the thermostat housing. Is it one with check balls, does it have hoses to the manifolds and the risers.
Do you have a photo of your engine that shows where your cooling hoses go.

You could also go to up to the Adults Only sticky at the top of the forum and download an OEM service manual for your engine. Check it out and let us know which type cooling system setup you have.

 

[JustJason]

Re: Hot Exhaust Risers.

thermostat has nothing to do with the riser temp. Neither does the engine side water circulator.
What temp are the risers actually at?
How about the temps on the sides of the manifolds... what do they look like?

Are the temps hi at idle but go down once driving the boat?
Do they start out low then get hot when the boat is driven? Or are they always hot?
What style manifolds do you have? Dry/wet? If they are the old manifolds they are probably wet.
What thermostat housing is on the engine?

Are we guessing here at a boat that is already at a shop?

And oh yeah... I can't believe you put old manifold/risers on a new engine too!

 

[JustJason]

Re: Hot Exhaust Risers.

Dam Don, ya beat me to it.

 

[GunHoInc]

Re: Hot Exhaust Risers.

Yes my boat is at the shop. But they seem to be going by process of ellimination so I thought I would post up here. I've only owned the boat 1 month and it's been in the shop for 3 weeks. The risers get hot as in I put my hands on them and can't hold them there too long. But Not scorched earth, Blistering, run around screaming like a Big Nancy Hot!?...

I bought the Boat for $4000.00 and found out the motor was bad. So my option was to make it a lawn ornament, or fix it. (Yeah, I'm a sucker)

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[Bondo]

Re: Hot Exhaust Risers.

The risers get hot as in I put my hands on them and can't hold them there too long. But Not scorched earth, Blistering, run around screaming like a Big Nancy Hot!?...

Ayuh,... I doubt you'll hold your hand on 140? risers,... Muchless 160? or more...
Your diagnostic tool tells me there's Nothing wrong there....

Did anybody have a Peek into/ at the manifolds,+ risers while they were Off the motors,..??

 

[GunHoInc]

Re: Hot Exhaust Risers.

They were going to Pull the risers this afternoon and take a look inside. I'm just curiouse here as I'm Pushing $6000.00 in repair bills on a boat I bought for $4000.00. And I'm wondering if I should say "Ok we are done."

But now you guys got me thinking about the hoses and I looked at other motors on the net and could they be on wrong?

Old motor before I had it replaced.

Another 5.7 off the web.

Another V-8 off the web.

Yet another V-8.

And again My new motor.

As you can see in the pics, the riser hoses on my old motor and new motor go to the top water neck. But in all the other pics of the other motors they don't and the hoses from the bottom of the motor go to the top water neck. Is my motor wrong?

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[Don S]

Re: Hot Exhaust Risers.

The hoses on the thermostat housing are hooked up to the wrong places.

Should be like this.

 

[lowkee]

Re: Hot Exhaust Risers.

HAHAHA! Fire your mechanic

 

[JustJason]

Re: Hot Exhaust Risers.

They don't call Don the "oracle" for nothing

 

[GunHoInc]

Re: Hot Exhaust Risers.

Thank You Guys VERY MUCH!

After I posted up I went home and got the CLYMER Mercruiser Shop Manual that the guy I bought the boat from gave me. And low and behold those hoses are on wrong. The Mechanic at the shop put them back on just like they came off of the old motor. "WRONG"

thanks, again. I'm heading to the shop first thing in the morning!

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[Don S]

Re: Hot Exhaust Risers.

Brings a whole new meaning to the words "A picture is worth a thousand words" doesn't it.

 

[GunHoInc]

Re: Hot Exhaust Risers.

I thought the exact same thing. Glad I took a pic of the motor today when I was there!?..

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[300sflyer]

Re: Hot Exhaust Risers.

Something tells me your mechanic is going to feel more than a little embarrassed, when you show him what is wrong.

 

[Don S]

Re: Hot Exhaust Risers.

Something tells me your mechanic is going to feel more than a little embarrassed, when you show him what is wrong.

Trust me, I am a marine mechanic, and I have made mistakes in the past, and still make them, and will probably make more in the future. The trick is, is how you recover from a real "Oh Sh*t" mistake, and have your customer come back the next time they have problems.