Logo
FULL SITE MENU

Merc 5.0 Alpha 1 Gen II Over Heating question

S

sguerrero

New member
First time out this season my boat over heated, it did great on the trailer when I checked everything out earlier this spring, I got water through the prop and all seemed fine. Engine Temp was right around 140. This is a used boat 1999 Monterey, that I have had for 3 yrs. and I am not sure when the impeller was replaced last, so I know I have that to do.

What is bugging me is that when it over heated I got water in the bilge, and there was steam coming from the back of the engine. Not a lot, but enough to get the auto bilge to kick on. I checked the baffle once I got the boat out of the water and it doesn't look damaged, so my question is where did the water\steam come from? Could I have popped a freeze plug on the back of the block, or is there a rubber coupler between the exhaust manifold and the out drive that I might have warped or melted? I noticed the temp was getting close to 200 and I shut it down. Never went over 200 while it was running. Any help would be greatly appreciated.

Thanks,

sg
 
or is there a rubber coupler between the exhaust manifold and the out drive that I might have warped or melted?
Click to expand...

Yes. There is one for each side of the engine that may have burned through during the overheat. It would have spilled hot water and steam into the bilge. The impeller should be replaced. You may need upper/lower housings since it overheated. You'll know when you get it out. Also check the condition of the gasket on the bottom of the upper half of the outdrive that the copper tube fits into. It may have been damaged. Look at the water shutters on top of the "Y" pipe; they were probably burned/melted. The engine did not overheat in the driveway because the hose water pressure acts like an impeller.
 
Last edited:
Well, I got to the bottom of the issue, it was the impeller, and found the water sources, the Exhaust riser tube on the bottom of the manifolds melted, thanks chiefalen. I also noticed a crack on one of the manifolds itself. Looks like I am getting new manifolds, they are full of corrosion, so I'm thinking best to replace them both and save me the hassle down the road.

The question is, do I go with stock replacements, or do I upgrade and if I upgrade what are my options. My wife and I are fine with not using the boat for the rest of the season, we have a sail boat we can use until this one gets fixed. So if it means being down for a while I'd prefer to do the job right and not rush to get it back on the water.

I know that there are options other than the cast iron manifolds which would save on weight and probably transfer heat better, but how much of the exhaust do I need to change out if I go this route? Will this require me to remove the engine? Any help or a point to resources would be greatly appreciated.

Thanks for your responses so far they have really been a help.

sg
 
I prefer OEM parts. I have heard good things about Osco and BARR (USA?) manifolds. I have heard bad/good things about GLM/Sierra (China). All are sold from this site. I believe aluminum mans. are available but the cost is pretty high.

You can buy a complete kit for the engine that has everything needed for replacing the manifolds/elbows. The exhaust tubes are separate. You'll probably need exhaust shutters also. See parts diagrams.

you need items 1, 3, 4, 5, 9, 11. Remember to get the quantities of bolts and manifolds/elbows needed for both sides. Don't use the old bolts.

http://www.mercruiserparts.com/Show...=100&bdesc=Exhaust+Manifold+And+Exhaust+Elbow

Get the rubber tube parts below:

http://www.mercruiserparts.com/Show...4.png&inbr=2697&bnbr=250&bdesc=Exhaust+System
 
Last edited:
If you are good with tools you can do the mani's the impeller everything yourself.

The mani's shoot the bolts with pb blaster.

Let sit.

Now look at the new bolts that came with your kit. See how long they are get down to home cheap-o or blows and buy 2 bolts that are 2 inch's or 3 inch's longer cut the heads off.

Now when you go to install the mani' screw in the cut off longer bolts into the 2 end holes, slip on the mani. Install the corrects bolts into the middle, and then remove and install the end bolts.

Me i like to chase the holes and vacuum them out.

I use grease on the threads so when i go to take out the bolts again they will just come out easy like.

But that's me.

I also like to put a drop of oil under the head of the bolt so you get a true torque.

Need more info just ask good luck !
 
Thanks Guys!

I have dropped the out drive and replaced the impeller. I have the Manifolds on order just waiting for them to arrive. The extra long bolts on the outside holes is brilliant, I would have fought the manifolds to get the first bolt started. I really appreciate all the great info. This isn't nearly as bad as I thought it was going to be when I first saw the water in the bilge.

I still have one part I can't find. When I pulled the lower unit to replace the impeller there was a plastic tube that sat on top of the water tube coupling assembly. it was melted and deformed so I can't find any numbers on it. the coupling assembly looks fine, I replaced the o-rings in it, but I'm pretty sure I need that upper plastic tube. everything is ready to go back together, I just need that tube before I put the lower unit back on.

Any help would be greatly appreciated. You guys have been really helpful so far Thanks a bunch!

sg
 
Back
Top