water in lower case

[musclehead]

Hi to all,this please is great keep up the good work.Here is my problem.I have my Greatgrand fathers 68 evinrude 18hp fastwin.The water pump failed and overheated the engine.We(my father and I) dismantled the lower unit and replaced the water impeller.during the test run(on boat in water)The motor ran fine for about 5 mins then died.before the motor stopped running a small stream of water was coming out of the top lower case where water has never came from before.We removed the spark plugs to find they were wet(gray milky water,Not clear).we decided to overhaul the power head.(note: have a clymer manuel).replaced headgasket,check for it being flat(all ok)replaced exhaust,plate gaskets and installed new thermostat.Reassembled and drum tested assembly.It staterd on the third pull.Now the problem.When running for about 45 sec- 1 min.The lower case seems to fill up with water and spraying out small hole in lower case @ the top.It looks like a casting relieve but not actualy supose to be a hole there.when water starts coming out this hole the motor boggs down and dies.My question is: Is ther suppose to be water all the way to the top of the lower unit and is there water suppose to be coming up from the waterpump where the drive shaft goes through the pump housing.I did not see a seal under the pump housing to seal off the drive shaft to pump housing..Sorry for the long post.I tried to give as much info as possible.<br />Thanks.

 

[Paul Moir]

Re: water in lower case

Welcome to Iboats, musclehead!<br /><br />On that outboard, most of the water should come out the large hole on the back of the midsection. Some water will come out the exhaust. The midsection should not fill completely with water, as there is a very large hole into it from the exhaust outlet, which is just aft of the propeller. <br /><br />Not much water comes out of that outlet until the engine warms up and the thermostat opens. I'm wondering if this is the action that stops the engine. It also acts as the idle exhaust relief for the engine, since the engine can't push it's exhaust down to the propeller until the boat gets moving.<br /><br />Naturally, the area where the water pump lives should be flooded with water, since all that is below the water line. But the midsection shouldn't fill up with water to the top.<br /><br />I hate to answer your question with another question, but is that large hole on the back of the midsection where the water is coming out? Is the exhaust down by the propeller plugged up with crud? <br /><br />I'm sure we can get to the bottom of this.

 

[musclehead]

Re: water in lower case

the small outlet on the back side does let some water out which is normal and out the exhaust side behind water intake,all seems to be normal.I just cannot figure out why water fills the whole lower unit.It seems that when water does fill up the lower section it is letting water get into the combustion chamber via the exhaust side.

 

[musclehead]

Re: water in lower case

The small hole where water is coming out would spray into the boat and onto the driver.this small hole is about 1 in below the bottom engine housing cover.It is close to the front side of the lower unit.

 

[Paul Moir]

Re: water in lower case

I think I understand you now. So this hole is actually part of the midsection of the outboard? (OMC called the middle of the outboard the lower unit for years, but most people mean the gearcase, driveshaft & water pump assembly when they say "lower unit")<br /><br />The forward section of that where the driveshaft runs, up by the block, is isolated from the rest of the cavity in the midsection. I guess that's to prevent exhaust gasses from cooking the bottom crankshaft seal. Anyway, water should never get into that area. I can only see two causes why water would be up in there:<br />1) The midsection is filling with water like you said. That is impossible unless the exhaust outlet behind the prop is completely blocked off. It should be wide open into the midsection area.<br /><br />2) The block base gasket is leaking, allowing water to escape into the cup shaped driveshaft cavity on the midsection, which protects the bottom crank seal and spline.<br /><br />#2 can't make the engine quit. Unless it happens to overheat at that exact second the cup fills due to water loss. So check out #1.<br /><br />There is normally some water going into the midsection - the exhaust relief passage allows some water to reenter the midsection, and there's a hole drilled in the water tube to squirt water into the hot exhaust. Exploded pictures can be seen at:<br /> http://epc.brp.com/default.aspx?brands=ej&lang=e <br /><br />But I've got to say, I'm still scratching my head!

 

[musclehead]

Re: water in lower case

thanks for your help.With the lower case removed from the midsection, in a 5 gal bucket, You can run drive shaft with elect.drill to operate the water pump.water starts coming out of the pump between pump housing and drive shaft,then it starts coming up the brass tube.there seems to be too much clearance between the drive shaft and pump housing letting water enter the drive shaft midsection area.Is there suppose to be a seal between the pump housing and drive shaft?or between the impeller and pump housing?I think this is where the problem is at.I have a vender that works on outboard motors on his spare time.He said he would come by and take a look.I will keep you posted on the outcome.Again Thanks for your help.I have been reading this site for about 3 months now and have learned a great deal.<br />I am a certified Dodge viper technition and very mechanically inclined.I have a 1100 hp supercharged viper that allways needs work but the little 18 hp motor is kicking my a!!.HA Ha BUT I AM DETERMINED TO FIND AND FIX THIS PROBLEM.

 

[Paul Moir]

Re: water in lower case

Oh, I see - it's really spraying hard out of the centre of the water pump? There's not supposed to be any seal in there but it is supposed to be relatively tight to the impeller. I wonder if they gave you the wrong one - do you still have the P/N?<br /><br />The impeller should fit the housing to about +/- a couple hundreths of an inch width wise, and they housing should be nice and flat. The stainless wear plate under it should be flat with no groove where the impeller runs.<br /><br />Just a thought - is it possible the impeller vanes are running in the wrong direction? They will right themselves normally but if they're lubricated with anything other than soap they can get stuck the wrong way.<br /><br />EDIT: Did some playing around with a good pump I have here. Water will shoot out of the small drain hole near the centre of the water pump housing if the outlet is blocked. This isn't a very high pressure pump, so even a small peice of the old impeller could be stopping it up. <br />Otherwise, it just runs slowly out the centre and really shoots out the outlet.

 

[musclehead]

Re: water in lower case

Hello again hope all is well.I have replaced entire pump assembly incl.new housing #313543.The clearance on the drive shaft is a little tighter.Reassembled and drum tested.Motor started after 3rd pull.after @45 sec.midsection filled with water and motor died.removed powerhead off entire assembly.Ran a drill motor on drive sahft with it still in drum.Found water filled midsection all the way to top at the drive shaft area of the midsection.during futher inspection I found where the water enters the powerhead.At the bottom of the powerhead,where the crankshaft protrudes out of the case,there is a small hole by the crankshaft.This small hole is some type of releive passage.It is actually under the last gasket of the reed plate .At least I know how the water enters the powerhead assembly.Now I need to find a way to stop water from comming up the driveshaft and entering the midsection.I am wondering what this small passage is for and if it can be plugged off.I know that is there for a perpose but find nothing in the manuel about it.The other Idea is to some how seal the drive shaft to pump housing better.I tried a o-ring between the impeller and housing but it made the assembly too tight and just burned out/tore the small rubber o-ring.any ideas would be helpfull.<br />If you could let me know how to upload pics for a better illustration for you.