Water in drain plug but oil clean 3.7L Mercruiser 165HP 1987

[Brock.Ward]

Basically I have been having issues with where I put coolant into the manifold, then the exhaust tube down the back of the engine gets hot. I replaced the impeller, checked for water flow all seemed good, hooked it back up and am assuming that maybe the impeller isnt working idk. Water is coming out by the impeller, a lot of it, so does that mean the water impeller is working? water wouldnt flow up the exhaust right thru the power steering line into the heat exchanger? I wish I had a diagram of how the water flows...nothing is clogged that I can see unless the exhaust elbow and tube down is...i am pretty sure if it had flapps they are burnt to a crisp. I am getting tired of this...

 

[stonyloam]

The hot raw water flows from the aft tube of the exchanger up through the power steering cooler into the exhaust elbow, and out. That should be cooling the exhaust. sounds like you are not getting enough flow through the exchanger. Did you take the front cap off and look for impeller pieces? You could try pulling the hose off of the aft fitting on the exchanger, stick the hose in there and see if you get free water flow out the outdrive, should be almost no backpressure. If your water flows through there chances are you have a blockage in the exchanger.

 

[Bondo]

The hot raw water flows from the aft tube of the exchanger up through the power steering cooler into the exhaust elbow, and out.

Ayuh,.... Take that hose Terry is talkin' 'bout, Off the exhaust riser/ elbow,....

At 1000/ 1200 rpms, Water should be Shootin' outa that hose,....

To post pictures here at iboats, post 'em at a photo hostin' site, 'n link 'em back here to yer posts,...
software here is abit screwy,....

'n this thread is for this problem,.... no need for startin' new threads 'bout the same ole issue,...

 

[Brock.Ward]

ya removed front cap found a few impeller pieces...seemed like it was still getting hot, maybe crap is stuck in the aft tube idk

 

[Brock.Ward]

where is the aft tube? Starboard side of the heat exchanger or in the rear?

 

[Brock.Ward]

nm cancel that i see what your saying, water does flow right out of the exhaust on the lower unit, out by the propeller full force...but i believe its still overheating just on exhaust as it was smoking and crackling...

 

[Bondo]

where is the aft tube? Starboard side of the heat exchanger or in the rear?

Ayuh,.... Fore is the pointy end of the boat,.... Aft is the squarish end,....

Take the hose off the exhaust connection, 'n check for flow,....
Use yer garden hose, 'n Stuff it into the various points, 'n flush out the entire system on the raw water side,...

 

[Brock.Ward]

No Title

see these pics, if the impeller is working water should flow out the exhaust by the propeller correct? Then it should be working right?

 

[Brock.Ward]

I have a feeling I installed the impeller the wrong way, holding the impeller house in my left hand and turning the impeller counter clockwise i believe is how i installed it with the fins...if i installed it with the fins pointing in the wrong direction that would probably cause no water moving upwards right?

 

[Brock.Ward]

i know exactly what i did, forgot to put that long black tube on the water impeller and just put the white tube on it....idiot...SMH, will I need to replace these flappers? Is it a must? Dont really get how that effect water going back in since its a closed system....

 

[stonyloam]

I have a feeling I installed the impeller the wrong way, holding the impeller house in my left hand and turning the impeller counter clockwise i believe is how i installed it with the fins...if i installed it with the fins pointing in the wrong direction that would probably cause no water moving upwards right?

Don't worry about that, it is impossible (even for me) to do it wrong. The impeller is offset in the housing so the veins are straight at one point, so first rotation of the impeller all will be well.

 

[stonyloam]

i know exactly what i did, forgot to put that long black tube on the water impeller and just put the white tube on it....idiot...SMH, will I need to replace these flappers? Is it a must? Dont really get how that effect water going back in since its a closed system....

Yeah that would do it LOL! OK, with the outdrive off, look up into the exhaust opening of the bellhousing to see if you can see a couple of flat "D" shaped metal pieces. They would be the remains of the shutters. If they are not there, they are either a: still hanging together, b: long gone or c: stuck in the exhaust. So with the outdrive off start her up for like 2 seconds to see if they come out. They should be there when you have the boat in the water, but for now don't worry about them. Put it back together and give it a try. The shutters come into play should you come off plain suddenly and the stern gets slapped with a big wave. With the engine off the wave could force water up the exhaust and into the exhaust manifold ( that is usually dry) and the water can enter the engine through open exhaust valves. The shutters fold to let exhaust pass but should open up and block water from entering the manifold.

 

[Brock.Ward]

ok, yea i am pretty sure they melted and shot out there were a bunch of pieces that shot out of the exhaust and are sitting around on the grass...ughhhh, i am sure once i pull the outdrive and add that long hose part it will work, i guess i'll worry about the shutters later or just be safe when i am slowing down to keep engine running and whatnot...Thanks so much guys..

 

[stonyloam]

Yeah that white tube is just a guide for the water tube. There is a plastic water cover up there that sometimes gets melted, but you probably had a ton of water shooting up there so probably is OK. When you go to do the shutters you should be able to just loosen all of the clamps on the bellows and work things apart. Maybe run a screwdriver around to get things to slide apart. When installing the new shutter stuff a rag in the pipe in case you drop something (just rember to pull it out LOL). Good luck!

 

[Brock.Ward]

Thanks Terry, im going to try to get that pipe back on tomorrow and hopefully run it if weather permits, want to ensure that the engine doesnt overheat or have any issues before I do anymore work to this thing...No creamy oil but you never know until you run it for a while, whats normal operated temp when i get everything running? 160-170? Any higher shut it down right away and check thermostat? Wondering if after i get it all running and its running great i should just sell this thing, dont want to have a head gasket issue which i hear happens a lot...if it wasnt replaced already, it has the alternator upgrade along with the 4" heat exchanger, now new impeller, new plugs, new trim motor and all new wiring...and i am just finishing up all the interior. gees its gonna be like new just dont want to then have engine blow on me.

 

[stonyloam]

Operating temp. 165 to 200F is in spec, but should stay 160-170F. Don't worry too much about the head gasket, replaced mine onc about 6 years ago, not bad for an 87. Keep it cool and you should be OK.

 

[Brock.Ward]

Hey one more question, do you think I can leave at least the bottom oil on the lower unit in, just drain a little so i dont waste what i just put in when taking it off again?

 

[stonyloam]

Just drain it into a clean container and put it back in.

 

[Brock.Ward]

Ok I am getting ready to run it again after I fixed the impeller housing again, had a question about the flaps. If its a closed cooling system how the heck can water come back thru a big wave and get into the engine since its a closed cooling system?

 

[salty3rd]

The exhaust from the engine goes out through the exhaust manifold and into the exhaust riser where it mixes with the raw water coming from the heat exchanger; then out the exhaust bellows. If a wave came up backwards through the exhaust; the water would go into the exhaust manifold and trickle down into the cylinders. The closed cooling part just cools the manifold. I have had two of these engines in my boat for 10+ years now and I have pretty much seen it all. They require a lot of TLC and a lot of patience. If your going to continue to work on this engine yourself I highly recommend getting the service manual..The manual has a diagram of the cooling system in it that is pretty easy to follow.