Hard to diagnose cooling water problem need some help.

[BillCon]

I, have one of my own strange issues to bring to light, I, have tried just about everything, I, have an 88' DT 175 runs great, has for a couple years, about few trips back I, noticed my water pressure gauge dropping from 30 to 20 to 10, at 5000 rpms, at idle it was at 10 now 0 and the tell tale was like a jet stream now just a trickle, and the alarms go off, so I, bought a "complete" water pump kit housing and all, and even the bushings and grommets that go to the copper pipe and drive shaft, when I, took the lower unit off, and the water pump, it still looked pretty good!, I, expected to see it worn out or pieces missing, so I, installed the new one in the right direction, made sure the half moon key was in and put it back together, fired it up in a big drum of water up higher than the water pump level and no water to the top of the motor still, I, took off the head covers and heads, replaced all the gaskets and thermostats cleaned up the insides didnt see anything out of normal, put back together and still no water coming up, by now I'm confused, so I, dropped the lower unit again put a hose directly on the copper pipe and ran the hose full force, no water coming up to the thermostats as I, removed them to see what happened, it comes out everywhere else , but now I, notice a lot of water coming down and out of the "drive shaft" hole next to the copper pipe, not sure if that is normal?, I, hope I,covered my tried procedures, Am I, missing something here? is there some other kind of part I, dont know about failed, I, can usually fix most problems but this one has me stumped thanks for any ideas.

[Solarman]

You're saying the water from the hose on the copper pipe comes out the chamber that the exhaust comes out (where the copper pipe goes up), or the next chamber over where the drive shaft is? I know it is very dark up the exhaust shaft, can you shine a good light up with water on, and see if you can tell where water is coming from?

It sounds like there's a problem with the mating surface between power head and midsection? Where is your water pressure gauge mounted? Is it near the drive shaft on your motor?

Post back when able. Do you have a manual on your motor?

[BillCon]

Hi, Solarman yes the water is coming back down the drive shaft hole and the exhaust, when I, plug up the drive shaft hole with a rag more water comes down the exhaust side, but doesnt come up to the thermostats unless, I, turn on the water full force to the copper pipe which is way more than a water pump can send up, then it will come out the thermostat holes, I, looked up into the upper leg with a strong light but couldnt see anything unusual, there has to be a pretty big leak or hole for that much water to by pass the power head like its doing, I, have a bore inspection camera at work I, will bring home and send up all the passages to see if I, can find anything, this didnt just happen at once it got progressive weak one minute strong the next, now no pressure at the top even with a hose connected, I'm usually pretty good at repairs but this ones got me!

[Solarman]

And where is your pressure gauge? The dt175 is the v-6 model with the exhaust cover in middle of cylinders on back, am I correct. I think the pressure gauge is located on the bottom of that cover also? I believe? I tried to view the parts for your motor, but not able to see the diagram.
I don't think it will do much good to open the exhaust cover to inspect that water jacket, but if your camera doesn't help, it may be possible to see the top area of the exhaust chamber, with your camera, especially the area where the powerhead mates with the midsection? Then turning water on, may see better from that area?
I am thinking you have deteriorated mating surface (from corrosion) under the powerhead, where it mates to midsection?

Post back what you find if able.

[BillCon]

No, it has 2 exhaust covers on each side, If you right, I, will have to pull the whole power head off to get at it, I, suspected there could be corrosion causing some problems maybe plugging up passages, but the weak then strong stream going back and forth is what was fooling me, now its just all coming out the bottom, I, will post pictures of the camera shots, thanks for the ideas to check.
http://www.brownspoint.com/store/pc/...175(87-92).pdf

[BillCon]

The pressure gauge is on the console, but the gauge tap is on the port side of the engine just in front of the lower part of the head next to the exhaust cover, that is the factory location, and yes I, do have 2 different manuals but they dont really cover that part in question, I, just ran the camera up into the exhaust ports, water tube and drive shaft hole, its really hard to see with the interior being black inside, but I, think there is something not right near top of the water tube area, its right next to the drive shaft, water is coming down there pretty fast, so I'm going to pull the upper leg off and then the exhaust housing, I, cant think of anything else to do except keep taking parts off until Its found unless somebody has run into this before and has a suggestion,thanks for any help.

[BillCon]

Update on cooling problem, it took me days to remove the seized bolts and get the exhaust manifolds and engine holder off and apart, but I, think I, have found the cause of the water flow issue, there was a moderate amount of build up, but in 2 areas there was heavy clogs, so I, bought a gallon of zep CLR and started soaking away and scraping the build ups, it turned out to be a major under taking, and snapped off 8 different bolts in the process, I, used to be a machinist, so drilling and tapping is not to much of a problem, for anyone else repairing Stainless Steel broken bolts, drill them with black cobalt bits,the cheap HF bits will not drill a clean straight hole and dull quickly, I'm just glad nothing is corroded thru and requires my long forgotten aluminum welding skills.

[Solarman]

Thnx for the update Bill. Thnx for the tip on black cobalt bits. Sorry it has become such a chore to clear up.

I would like to ask, were you diligent in flushing your motor after each use in the past? You seem to be very thorough and careful in disassembly and repairs. Will you do anything different in the future that might help prevent this from happening again? Or, maybe the first sign of pressure drop, might be a good time to go for an extensive flush treatment?

Good luck, hope you're back out on the water soon. Post back if you find anything else.

[BillCon]

I, bought this motor about 4 years ago so I, dont know how much was built up before, I, only use it in salt water, and I, always flushed the engine 15 mins when its home, I, thought I, was preventing it, so its kind of a mystery as to why it happened, this was slowly getting worse, I, may have to think about trying some type of chemical flush every so often to keep it down, or unless somebody in the forums here has an idea to keep it from happening again, this was a real pain to undo, your suggestion led me to tearing down the bottom end and I'm glad you did, the motor runs like a rapped ape, but I, almost lost it with this problem, maybe this thread will let some other members know, dont let an over heating problem go, get on it quick or you will loose your motor. I, will update as this will take me another week to undo.

[BillCon]

Ok, the final update to the diagnosis of no water flow, well after completely tearing down the the upper leg and and all its components and replacing the water pump only to find still no water flowing up in the block I, pulled the heads off and and found the problem, both parts in the bottom of the heads that separates the incoming flow from the return discharge flows had corroded thru bypassing the waters push up thru the cyclinders, I, assumed it was the pump as it most often is, I, tried to up load pictures but they were to many pixels for the site, but after cleaning with muratic acid, I, proceeded to rebuild the missing dividers with the aluminium wire welder and a dremel to grind back down the excess, it took about 3 hours to reshape them, I, never would have expected to find that kind of failure hope this helps others to look at the heads too when the water pump change doesnt do it, so I, guess the lesson here is to never assume anything,!

[Moonlighter]

Well, you wouldn't have expected that! Great detective work to get it sorted at last. Have you got it all back together and given it a run yet?

Regarding a flush procedure to keep it clean in future, if you go to The Hull Truth website or even just google "vinegar flush outboard motor" there is a great thread there detailing how this has proven successful for a number of people, and the best thing is that the vinegar is quite inexpensive.

[Solarman]

Bill con,
Are you saying that you had heavy blockage under the powerhead where it bolts to the midsection, and then found more problems in the cylinder heads also?

To me that seems extreme. I guess our attempts at flushing are only good to an extent. We might all consider a regular yearly vinegar/ chemical corrosion flush prior to our last couple trips out, before storage at end of season. Unless it is possible to flush some non-reactive, protective lubricant/ penetrant, something that will flush away when Storeage ends? Maybe a quick flush with a couple gallons of propylene glycol (non toxic antifreeze)? Should be safe for aluminum pas-sages, and rubber?

I believe you have flushed well, think i'm going to try the propylene flush. I seem to have a bearing that's making a noise, so know I have to go in, wanted to wait, but might better get it now type noise. Then I can see what it looks like after the flush?

Let us know how your going when able. And how the motor runs when done. Good luck.
-Ralph.

[BillCon]

Yes, Its back together and running great, the water pressure is 20psi at idle,shoots up to 45 running, there was some heavy build up all thru the upper leg champers, but not stopped up completely, I, took it completely apart all the way up to the bottom of the block, for some reason the corrosion really concentrated itself in the lower parts of the head, I, use the white vinegar flush twice a year, but bear in mind this could have been old damage and build up since its and 87' model 175, Solarman when you really get into the motor for the bearing you will see why it doesnt flush to good there is no way to clean it up without taking is apart, I, used straight muratic acid on the parts and a pick and screw driver and wire brush they cleaned up in about 3 to 5 mins then wash them off good, use outside with a mask, glasses and gloves, that stuff is hostile, nothing else would touch the calcium lime, salt and oxidation build up, the heads just plain blew thru the water jacket chambers in the bottom separations, there was no other choice but welding and grinding to restore them, if I, can figure out how to down size the pictures I, will post them, mans best friend is not a dog, its an aluminum wire welder!