470 overheating, is this normal flow through the heat exchanger?

[dccordell]

Hey guys, finally got the boat on the water today for the first real test run (after a fail last weekend with a busted steering cable). The motor runs good as does everything else, but it overheats. While idling, it will sit at 180. Very soon after putting in gear, it will creep up to around 200 almost, not quite hot enough to trip my overheat alarm, but very close I think.

The impeller is new, heat exchanger was cleaned out, all engine coolant replaced with 50/50, new thermostat (160 degrees), and new radiator cap.

I pulled the aft hose on the heat exchanger (that goes to the exhaust elbow). I put the garden hose into that hose, and got a ton of water out of the exhaust relief ports on the drive, as well as the little drain hole on the bottom of the drive. So I think the exhaust side is clear.

So I hooked the muffs back up to the drive, and fired up the motor for a few seconds to see how much flow from the drive and impeller I was getting. Here is a video of the amount of water going through from the garden hose. Does this look like a normal amount of water to get pumped through, or should there be more and I should look for a blockage somewhere between the input hose on the transom plate and the heat exchanger?

Thanks for any help, trying to get it straightened out for another run tomorrow! It's great to finally see the years of hard work on the water! :joyous:

 

[Eric 3.7LX Alpha 1]

Re: 470 overheating, is this normal flow through the heat exchanger?

You can test the water flow from the outdrive into the voltage regulator (if it's still there), to ensure the drive is giving you enough water. This test is in the water not on muffs.

At least that can eliminate the drive as an issue.
View attachment 82_04.pdf

 

[stonyloam]

Re: 470 overheating, is this normal flow through the heat exchanger?

That didn't look bad for idle. Time to make sure the temperature gauge is reading correctly

 

[dccordell]

Re: 470 overheating, is this normal flow through the heat exchanger?

I believe the gauge is working correctly, I checked it with an IR gun to make sure and it seemed pretty close.

I wish I would have pulled the hose from the voltage reg. to check the flow while we were still at the lake. Since it seems that the flow through the heat exchanger is acceptable, what should I check next?

I'm wondering if there is a blockage in the exhaust, somewhere after the exhaust pipe. The original shutters were completely gone, and I never found them. I wonder if this could be the problem?

One thing to note is that when the engine is on muffs idling, there is only water coming from the starboard side exhaust relief port, nothing from the port side. Is this normal? There is also a small stream from the prop, but not much.

 

[stonyloam]

Re: 470 overheating, is this normal flow through the heat exchanger?

Could be that the impellere pump housing is worn. Might try replacing the whole pump assembly with OEM parts. Are you losing any coolant?

 

[dccordell]

Re: 470 overheating, is this normal flow through the heat exchanger?

Not losing any coolant that I know of.

Here is a couple pics of the impeller and housing. What do you think? This impeller is basically brand new except for a few runs on muffs and the test run in the lake today.

 

[Bt Doctur]

Re: 470 overheating, is this normal flow through the heat exchanger?

It looks like the rubber has slippedoff the pump core. try pulling the rubber away from the core. if you can even move it a little the impeller is done.

 

[dccordell]

Re: 470 overheating, is this normal flow through the heat exchanger?

Bt, I knew that impeller core looked funny but I didn't think that the core may be spinning in the impeller. Is this what you think could be happening? I'll give it a check as soon as I can, probably in the morning.

 

[stonyloam]

Re: 470 overheating, is this normal flow through the heat exchanger?

Yeas, just doesn't look right. Still think it would be a good idea to instal a new OEM pump housing and impeller, then you will know you are OK. IMHO

 

[Bt Doctur]

Re: 470 overheating, is this normal flow through the heat exchanger?

Merc and Sierra both had a bad batch get by.The rubber was not bonded correctly to the core and woould start slipping.
All the ones i`ve seen have had the wavy appearance and the rubber could be pulled away with your fingers

 

[dccordell]

Re: 470 overheating, is this normal flow through the heat exchanger?

Alright, will be checking in the morning, and I'll probably go ahead and replace the whole setup anyways since I'm already down and out for this weekend.

 

[dccordell]

Re: 470 overheating, is this normal flow through the heat exchanger?

Quick question: Does iboats not sell the Mercruiser pump housings and impellers? All I see is Sierra and Mallory.

Edit: Since I can't find the kit on iboats, is this the kit that I would need for all of the parts? I have a #1 drive (S/n: 5691256).

According to the PDF for changing the impeller on Mercruiser drives that is floating around, this is the kit that I would need, but I want to make sure first.

 

[stonyloam]

Re: 470 overheating, is this normal flow through the heat exchanger?

As far as I know they do not. Try your local Mercruiser dealer. Or these guys The #1 web site for genuine Mercury Mercruiser engines, parts and propellers part # 46-96148Q8

 

[Eric 3.7LX Alpha 1]

Re: 470 overheating, is this normal flow through the heat exchanger?

Unfortunately... Iboats doesn't sell Quicksilver, as Terry mentioned, they should be a stock item for your local Mercruiser dealer or search online.

 

[dccordell]

Re: 470 overheating, is this normal flow through the heat exchanger?

.. these guys The #1 web site for genuine Mercury Mercruiser engines, parts and propellers part # 46-96148Q8

I have used these guys for everything engine-related in the past, but it seems their shipping to my area has gone way up lately. Over $17 to ship this pump kit UPS ground, that's a little too pricey for me these days... so I'm forced to look elsewhere, as much as I hate to.

I think I'll check locally at the shop first, although the last time I went in looking for parts for an MC-1 drive, they didn't seem too interested.

I'll be checking out that impeller here in a few minutes, and will let you guys know how it looks!

 

[stonyloam]

Re: 470 overheating, is this normal flow through the heat exchanger?

You can try e-bay, just make sure it is OEM. I like to get stuff from my local dealer, a little more expensive, but they are willing to help out with advice when I run into a problem.

 

[Bt Doctur]

Re: 470 overheating, is this normal flow through the heat exchanger?

This is what were talking about,Cust had a above idle 1500 rpm overheat. Reduce to under 1500 and it was ok, above it runs hot.
This was only 3 weeks old.

 

[dccordell]

Re: 470 overheating, is this normal flow through the heat exchanger?

Well, the impeller doesn't seem to be separated from the core as far as I can tell. I pull on the impeller away from the core and it seems well attached all the way around on both sides.

I wonder if it's possible that the core is actually spinning within the impeller, and it gets hot enough to melt the rubber and is stuck back to the core after the engine is turned off and the melted rubber cools? Just a thought, doesn't seem likely though...

I'll be replacing the impeller and housing anyways, just to knock that off the list.

 

[dccordell]

Re: 470 overheating, is this normal flow through the heat exchanger?

Ok so the local Merc shop has the impeller/housing kit in stock, so I'll be picking that up in a little bit.

When I pulled the sea water hose from the intake part of the voltage regulator and ran the engine for a few seconds to verify sea water flow out of the disconnected hose, I also noticed that there was water being pushed back out of the voltage regulator where I removed the hose. Is it normal for water to be able to go backwards out of the voltage regulator with this hose removed?

It seems like the only way water could be pushed through the voltage regulator in reverse (with the sea water hose removed) would be if the exhaust gases were being pushed from the exhaust elbow into the heat exchanger, pushing water back out through the regulator. Is this normal, or a sign of other problems?

 

[stonyloam]

Re: 470 overheating, is this normal flow through the heat exchanger?

Yes the water in the hose going to the elbow and the water in the exchanger would be pushed back out by the exhaust gasses. Normal.