Merc 170 3.7L Cooling System Question and Water Pump Repair

[Drewmeister]

Re: Merc 170 3.7L Cooling System Question and Water Pump Repair

Terry (and All), so I followed your advice and instructions and got the drives back together. The one thing I was doing wrong (and you can laugh at me all you want because it WAS stupid) is that when the lower drive came off, it brought the copper draw tube with it. SO, I was putting the draw tube in the pump outlet, rather than putting it in the upper drive section. So essentially the guide tube was useless. Sometime I amaze myself at foolishness like that. I have a Ph.D in Mechanical Engineering, by the way. I was looking at it going HOW THE HELL DO I DO THIS!?! and I wanted to smack myself for being so stupid. My brother in law, who was helping me, gave me the funniest look when I told him the draw tube would come out of the pump. He is like, "If you told me that it would make sense more to me what the "guide tube" does."

OK, so getting the forward and reverse gears aligned worked out just fine, you are the man Terry, but aligning the splines on the main drive shaft is hard because you can't see up inside. I assume I got it right. I got the two sections back together with some brute force, using a C-clap to hold the lower drive on helps alot!

Now the trouble is, there is STILL no flow to the HX, all of the water is coming out of the upper drive, so apparently there is a major leak somewhere. I am proceeding with taking the upper and lower drive off to find the leak.

Any thoughts/suggestions appreciated. While I have it all off, I will replace the main exhaust bellows, as it is broken into to parts, which does not allow exhaust gases and water to go through the prop.

Having "fun" here, but still no taking the boat out yet. My brother in law is having fun too!

Drew...

 

[Rocky_Road]

Re: Merc 170 3.7L Cooling System Question and Water Pump Repair

Very important...was the old rubber impeller intact? Or were there pieces missing....

BTW: when running on the driveway 'muffs'...and idleing...most of the water will be exiting around the transom bell housing through the relief ports. Very little will be coming from the prop.

Happy boating!

 

[Drewmeister]

Re: Merc 170 3.7L Cooling System Question and Water Pump Repair

Rocky, the impeller was cracked in alot of places and had chunks missing.

When idling for a minute or two, I took the water exit line off the HX and there was no flow at all.

 

[Rocky_Road]

Re: Merc 170 3.7L Cooling System Question and Water Pump Repair

Rocky, the impeller was cracked in alot of places and had chunks missing.

When idling for a minute or two, I took the water exit line off the HX and there was no flow at all.

You will need to find the missing pieces...they are still in your cooling water pathway. I wonder is there is a way to 'backflush' the hose to the HX? Maybe you can drop the lower again and force water from where the hose attaches to you heat exchanger towards the pump...?

Happy boating!

 

[stonyloam]

Re: Merc 170 3.7L Cooling System Question and Water Pump Repair

The restriction point is under the forward HX endcap starboard side (of the HX). Anything larger than the tubes should be there. You could try taking off the inlet line and see if you have flow there. The other possibility is a kink in the hose between the bellhousing and the transom.

 

[Drewmeister]

Re: Merc 170 3.7L Cooling System Question and Water Pump Repair

Actually, looked at the impeller again and no "chunks" missing, just lots of cracks. Looked at the inlet tube to the HX and it is fine, as is the cooling in end of the HX cavity. So at this point, I plan to take the whole upper and lower outdrive assembly off and check it out as well as replacing the exhaust bellows.

Sure I could hook up a garden hose to the CW inlet line to the HX and let it flow back to the CW intake on the lower outdrive.

Drew...

 

[Drewmeister]

Re: Merc 170 3.7L Cooling System Question and Water Pump Repair

I re-checked the old impeller and there are not piece missing. I also check the HX inlet tube and took the end cap off and found nothing. Question on the HX. to clean the tubes, what do most people use? I have some good copper and SS cleaners from my brewing stuff, such as barkeepers friend, which do a good job of cleaning copper to a shine.

The issue here is I have NO flow of water to the HX. The tubes at the inlet and exit are dry. Water from the pump is leaking out the upper drive unit...could be from pressure from hose or from pump, I don't know which. Is my next step to putt the whole drive and examine things in the upper drive? That's my plan right now.

Drew...

 

[glennj3]

Re: Merc 170 3.7L Cooling System Question and Water Pump Repair

Hi, this is my first night on the boat forum and you guys are right on what I have been doing the past week! 2 wks ago I was in Charleston SC harbor, she ran hot after 15 minutes out the 2 nd day. I shut her down just as soon as she started running rough.
So, I learned how to drop only the lower housing, leaving the upper in tact. Used a hydraulic jack under the fin to assist me in replacing her up into the upper. Worked very well.

Problem is I have taken the lower unit off so many times now I could do it blind folded. The first time I replaced it, I used a hose and the water muffs, turned her on, cranked up and ran great. Soon the temps were hitting 175 F. shut her down. She was running hot. I noticed no water was coming out near the housing at the boat. Moving up to today, I had to replace the new water impeller with all new due to the heat from the exhaust melted and hardened the impeller. The problem seems to be, and I am new at this but with the lower unit off the boat, put on the water muffs, no water comes up through the pump and the water brass tube. Don't you think water should flow up easily right through the water pump housing? With the pump off I can see down to the vents on the boot, so it is open. I assured the gaskets are on correctly and the impeller is on clockwise, not that that should stop water flow.
Any help will be greatly apreciated. PS, I have the alpha 1, mercruiser 170 engine.

Glenn

 

[Drewmeister]

Re: Merc 170 3.7L Cooling System Question and Water Pump Repair

Glenn,

When you run with the muffs on you are saying there ISN'T water come out near the bell housing (the next piece after the upper drive going towards the engine)? My problem is ALL the water is coming out there! I found that the water transfer hose from the upper drive through the bell housing is badly dry rotten on my engine and needs replaced. I HOPE this is my last issue with this!

One thing I am going to try tonight (now that the torrent of rain since Sunday has subsided) is to take a hose and backflush from the HX inlet tube. My bet is most of the water comes through the bell housing water xfer tube and does not make it to the water inlet gills.

Drew...

 

[GarySequim]

Re: Merc 170 3.7L Cooling System Question and Water Pump Repair



I'll answer the easy stuff LOL
1) I would not do that, because that deprives the exhaust of cooling water and you can burn up your exhaust shutters and rubber engine exhaust bellows (all that rubber stuff back there).

2) Don't do that either. When it is running take a look at the lower starboard side of the pump. Is it leaking? If not don't worry about it.

3) Again, don't mess with it yet. Normal operating temp is 165-200 F, so you are OK.

On the muffs with it running, carefully feel the pipe going into the front of the HX. Should be cold (seawater inlet). That tells you you have flow coming in. Your water exits the HX through the aft outlet and the hose (should not be real hot) goes up to the exhaust elbow where it exits the engine.

The very first thing you need to do is replace the impeller in the outdrive to make sure you have good flow into the HX. Replace the impeller and housing both. Someone will give you a link to the manual

Go to Autozone and borrow the tools to do a compression test and cooling system check. If they are OK you should be in good shape

Here is a link to your engine manual: http://www.4shared.com/document/zTbCbkDD/Service_Manual_08.html

Welcome to the 470 owners club

Attached is a manual I made for my 3.7l Alpha One Gen One, based on a number of good sources. Mine is reorganized so the impeller replacement work explained in a more logical order than the books I found.

 

[achris]

Attached is a manual I made for my 3.7l Alpha One Gen One, based on a number of good sources. Mine is reorganized so the impeller replacement work explained in a more logical order than the books I found.

10 year old thread. Please read the forum rules regarding old threads.