Forgot to reseal silicone seal in front of water pump

[JimMM]

Just replaced all the seals and water pump in a 1995 200HP Merc. It's back in the water but I now realize I forgot to put a fresh bead of silicone on the baffle between the water pump and the exhaust. The silicone from the last service is still there intact although it's stuck to the lower unit, but the drive shaft housing side let loose when the lower unit was dropped. How necessary is it to put a new bead of silicone on the baffle during reassembly? The cured silicone from the previous assemble is still there intact attached to the baffle, so it's somewhat "sealed" just not "glued" to the driveshaft housing on the top. Drag it back out of the water, drop the lower unit and put a bead of silicone in there? I take the boat out of the water if a major hurricane is coming and replace the water pump at least every other season. Think it's OK to leave it be until the next water pump service? Where does any exhaust that leaks through the silicone seal go? Up the crankshaft housing to cowl? Or out that square hole in the center rear top of the crankshaft housing lined with a rubber grommet? Will exhaust heat ruin the water pump impeller even though it's submerged in water?

 

[Dukedog]

will be jus fine....

 

[JimMM]

will be jus fine....

I like that answer! I've always wondered why they engineered such a kludgey way of keeping exhaust out of the drive shaft column, especially on an interface that has to be frequently opened for recommended maintenance (water pump)..

 

[Dukedog]

me to.. you would think if its that important they would have come up with a gasket of sorts.... i never worried 'bout it with any of my junk since they were all hot rods anyway.. no can, drilled exhaust.. never a problem with pump meltin'........... jus tha little plastic guide for tha pump tube!!!

 

[JimMM]

me to.. you would think if its that important they would have come up with a gasket of sorts.... i never worried 'bout it with any of my junk since they were all hot rods anyway.. no can, drilled exhaust.. never a problem with pump meltin'........... jus tha little plastic guide for tha pump tube!!!

So it does get hot enough to melt that plastic guide tube? … wow ... assuming it's got water going through it, that's surprising. Oh well, I guess I'll find out what if any damage is going on when I take down the lower unit for the next water pump maintenance, or if the engine overheats …whichever comes first .. eeek,

 

[Dukedog]

So it does get hot enough to melt that plastic guide tube? … wow ...

thats a hot rod deal.. ya pull tha can that directs 99% of tha exhaust out tha hub around/thru tha prop.. no exhaust in that part of tha down housing with production can in it....

 

[Dukedog]

won't let me edit.. jus ta clarify tha "can" creates a separate passage for exhaust to tha prop/hub.. removing it makes tha whole down housing an exhaust exit............. and really loud.

 

[AceDuece]

I'm not sure if I should have used some silicon or not. Post water pump impeller change I have what appears to be exhaust sludge exiting my water intake holes after my outboard is ran. My lower unit pressure tested fine, and the fluid looked fine as well. With 4-5 hours of run time on the boat, I'd have assumed that if my vertical shaft or shift shaft seals had gone bad and were causing the sludge out the water intake vents that my lower unit oil would look like a milkshake.

I think I'm going to run it a bit and see what happens. I definitely did not put any silicon on the lower on my 40hp though when I did the impeller...so maybe there's something to it.

 

[Dukedog]

anytime you have anything but exhaust gases and water comin' out tha bottom ya have a problem of sorts.... tha silicone bead has nothing ta do with it... lotta times its fuel/oil mix and water when something with fuel delivery has a problem.. if gear case checks out then ya might look elsewhere in tha motor and/or fuel delivery itself........ jmo.

 

[AceDuece]

anytime you have anything but exhaust gases and water comin' out tha bottom ya have a problem of sorts.... tha silicone bead has nothing ta do with it... lotta times its fuel/oil mix and water when something with fuel delivery has a problem.. if gear case checks out then ya might look elsewhere in tha motor and/or fuel delivery itself........ jmo.

We're on the same page. My compression tester will be here today, that's where I'm starting. I trolled with it for those 4-5 basically at an idle and I think I loaded everything up. Also who knows how old this fuel is (boat is new to me). I drained one of the tanks yesterday. Time to start with some fresh rec 90 and a decarb'ing.

 

[JimMM]

Post water pump impeller change I have what appears to be exhaust sludge exiting my water intake holes after my outboard is ran..

If this just started after an impeller change you might want to double check the reassembly of the pump. Sounds like exhaust is leaking into the water pump if you're getting exhaust sludge out of the water intakes holes. Make sure all the gaskets are installed above and below the water pump base plate and aren't torn, folded, etc., and that nothing is lodged under the pump housing keeping it from sealing down onto it's base especially around the pump's intake port.

 

[Dukedog]

don't think water and exhaust mixture will make "sludge"?

 

[AceDuece]

don't think water and exhaust mixture will make "sludge"?

Maybe word choice was poor there. It looks like the same 2 stroke oil mess that oozes down the skeg out the exhaust.

I've never seen one ooze that mess out of the water intakes though.

 

[Dukedog]

i've seen it a coupla times with tha hot rod stuff.. no can.. completely empty down housing.. it was usually unburnt fuel/water mix... but its a merc so who knows for sure at this point!

 

[JimMM]

Did you remember to put back the rubber seal between the guide tube and the impeller housing? It's often forgotten. If not, unburnt hydrocarbons getting past the unsiliconed baffle will condense on the outside of the cold water tube and drain down into the pump and out the intakes. Other than that, check the cooling baffle to exhaust manifold gaskets and possibly the head gasket. Maybe the extra water pressure from the new impeller found or created a opening between the exhaust and water jacket.

 

[AceDuece]

Did you remember to put back the rubber seal between the guide tube and the impeller housing? It's often forgotten. If not, unburnt hydrocarbons getting past the unsiliconed baffle will condense on the outside of the cold water tube and drain down into the pump and out the intakes. Other than that, check the cooling baffle to exhaust manifold gaskets and possibly the head gasket. Maybe the extra water pressure from the new impeller found or created a opening between the exhaust and water jacket.

You might be onto something. I just pulled up the microfiche, I know that the tube piece 38452 is there, but don't remember seeing part 38453 listed as washer...but that looks like a seal to me.

 

[JimMM]

There are also two nylon washers on either side of the impeller that often get left out. These keep the impeller with proper clearance from the metal cover top and bottom plate. If one or both of these are left out severe pressure and wear on the impeller along with any lubricant you put in the pump for to handle the dry start, can cause a slurry of lubricant, impeller material and water to come out the intake ports. Also check your water pickup tube to make sure nothing is up in it that died. I don't know about the 40HP but on my bigger Merc, there is a rubber slinger on the drive shaft that snugs up against the top of the water pump. It doesn't show up on a lot of microfiche blowups for some reason.