50HP Merc not pumping water, Missing seals or Gaskets???

[zbhover]

Hello everyone, I just joined this group to try to get my grandpas outboard working for him again.

First of all I don't know much about outboards, I build hovercrafts, am building a v8 powered VW bug and work as an industrial mechanic so I have the mechanical abilities, but not the experience with outboards.....

At the end of last season my grandpas 1977 50hp merc stopped pumping water out of the tell tale. He had this happen a few years ago and he had to have the impeller replaced so he figured it was the same thing again. Except now he's retired and doesn't have the money to hire it done.

So I ordered a impeller repair kit and put it on this weekend. The old impeller was in rough shape, but not too horrible looking. I put it back together just as I took it apart and am confident that I put everything back together correctly, or at least the way it was when I took it apart, but its still not pumping water.....

He also had a mouse make a nest in it this winter and ate through a bunch of wires and a gas line. I re wired the engine and put on new gas lines, and the engine starts right up and runs great, but its not pumping water. Just a dribble out of the tell tale and I didn't notice anything coming out of the exhaust either.

I pulled the hose off of the tell tale and it was clear, I can blow air through the hose into the engine without restriction, and I also pulled the L/U back off and I can blow air up the water tube also with no restriction.

Any clue what else this could be??? And how I might go about fixing it???

Could a bad thermostat do this??? Maybe a rubber hose rotted off where it connects to the engine??? or???

Does anyone have a breakdown of the cooling system so I could see whats going on, or a breakdown of the engine so I could pull the lower housing off of the engine???

Any help would be appreciated.......... My grandparents are itching to get back out and do some fishing...............


THANKS for your time!!!!!!!!

 

[jeffdjpeat]

Re: 40HP Merc not pumping water

Re: 40HP Merc not pumping water

im in the middle of repairing a similar issue with no luck. but i can tell what i have done. Remove the lower unit, while in reverse so you can spin the prop and line it all back up later. tear apart the pump housing, replace all gaskets and the impeller, check that the fins below the pump housing are clear. possibly pump water from the intake hose connected to the water pump, up through the motor with a garden hose, does this shoot a good tell-tale? when installing the new impeller make sure its the right way, i messed this up and tore 2 fins off, my 1986 merc 60hp requires the fins to be turned clockwise while pushing the housing onto it. other then that, mines still not pumping water, but talking to a pro i know i have done that much right. my pump housing was completely toast, its getting replaced tomorrow, but i wish you luck!! thermostats can be a problem, if you have one i would change it for the cost.

 

[zbhover]

Re: 50HP Merc not pumping water

Re: 50HP Merc not pumping water

Thanks for the ideas, I put the impeller and gaskets in the same way the old one came out so I don't think that's the problem, and I took it apart 2 more times to check everything and the impeller still looked good. The pump body was still in good shape, so I think I'm fine there. We were working on the engine at his camper so we didn't have any running water at the time to try to squirt some water through it, but I think the water is getting turned on this week.

I guess I'll try to find a breakdown of the outboard and start tearing into it and see if I can find something wrong......... I'll check the t-stat.......... Any clue where its at and whats I need to do to remove it?????



Anyone else have any ideas????????


THANKS!!!

 

[Joseph10]

Re: 50HP Merc not pumping water

Re: 50HP Merc not pumping water

I am assuming there is a pin with a slot in the shaft on this model (slides in a groove on the shaft and a groove on the impeller)? Was the pin by any chance damaged or missing (sort of like a shear pin)? If so, the impeller would not spin with the shaft.

Also, I have never pulled the thermostat housing on my 50, but I did on a 115 I used to own. The way that motor was designed - water would come out of the tell-tale even with the thermostat shut. Not sure how your motor is designed, but I would think you would see water even if the thermo is shut/frozen.

 

[Joseph10]

Re: 50HP Merc not pumping water

Re: 50HP Merc not pumping water

Also could try putting on the muffs and turn the hose on full blast. You might have a mud dobber nest clogging the water tube. If a weak stream of water comes out with just the hose turned on, then that is not the problem

 

[potterp]

Re: 50HP Merc not pumping water

Re: 50HP Merc not pumping water

I'm having the same problem with my 40hp merc. I've done many impeller changes and this is the first time this has happened. I cannot get it to flow water even with the ears on. I did put the hose right on the tube that the impeller pumps into and it flow through the engine and out the tell tale fine. There is no restriction under the impeller. I even spun the impeller with a drill and socket on the shaft whill it was sitting in a cooler full of water and it did pump. Not a real strong stream of water but it was pumping.
The water cooling diagram for the 40hp shows that the water will flow to the tell tale because it is y'd off before the thermostat. I'm working on mine today so hopefully I find out more.

 

[potterp]

Re: 50HP Merc not pumping water

Re: 50HP Merc not pumping water

This may sound weird but I decided to look into the timing to see if maybe this was a problem that was keeping the engine from running properly hence not pumping water properly. Sounded like a long shot but I tried everything else. After checking alot of stuff I found the plug wires swapped. My nephew was the last to use the boat so no telling when this happened. The boat would run but it was hard to start and just wasn't what I thought it should be running like. After swapping the plug wires to the correct cylinder the engine started like brand new and the impeller pumped like it should. I never thought at first to check this because I did not mess with the wires.
Just check yours to be safe. On mine (and I think most mercs) the number one cylinder is the top one.
Now that my four day weekend is over I finally have the boat running. Go figure! Oh well, theres always next weekend.

 

[zbhover]

Re: 50HP Merc not pumping water

Re: 50HP Merc not pumping water

There impeller has a half round key in it that goes into a notch in the shaft, so I know the impeller is spinning.

I also don't think its a problem with the plug wires being swapped.... It starts right up as soon as you hit the ign. and runs great....... I just doesn't pump water

We'll have running water this weekend so I'll give that a try and see what happens.

Does anyone have a breakdown of these outboards so I can figure out how to start tearing it apart if need be??????????????


Thanks for the idea's guys....

 

[floatingwoody2006]

Re: 50HP Merc not pumping water

Re: 50HP Merc not pumping water

these older mercs will not pump correctly on muffs..At least neither of my 2 do.. ANd this is with new impellers. You need to submerge them in a barrel and try again. I am thinking poor design of the tell tale location may be the culprit. edit..I also shoot a good stream of carb cleaner thru the tell tale to loosen things up if it doesn't start pumping right away..good luck.

 

[gonelong]

Re: 50HP Merc not pumping water

Re: 50HP Merc not pumping water

these older mercs will not pump correctly on muffs..At least neither of my 2 do.. ANd this is with new impellers. You need to submerge them in a barrel and try again. I am thinking poor design of the tell tale location may be the culprit. edit..I also shoot a good stream of carb cleaner thru the tell tale to loosen things up if it doesn't start pumping right away..good luck.

My '77 50 HP had the same problem. I suggest having someone stand with their hands on the water jacket as you let it idle for a bit. If the water jacket is staying cool I'd give it a bit of gas.

http://forums.iboats.com/showthread.php?t=194296

It took me a bit to get the motor started, but once it did, no problems keeping it running at idle speed. Still, no water out the pee-hole, though the water jacket on the motor was nice and cool. I let this run for 3-4 minutes with my hand on the water jacket which was staying cool (before it'd get hot in seconds), but still no water coming out the tell-tale.

Finally I couldn't stand it and pushed the throttle up a bit ... and ... she pee'd like a champ. Nice luke-warm stream with the water jacket staying very cool. The tub was big enough to allow me to slip in into gear which it ran at idle without stalling. I gave it a bit of gas and blew a bunch of water out of the tub so I shut it down immediately. Ready to go!

 

[jeffdjpeat]

Re: 50HP Merc not pumping water, replaced impeller now what???

Re: 50HP Merc not pumping water, replaced impeller now what???

look at the post help help help, with 37 replies. that was mine. i tore that thing apart 20 times in 5 days. finally i bought the entire water pump, lower and upper housing, gaskets etc.. i have a suspicion that there wasnt a good seal, or no seal under the lower pump housing, causing air to enter, exhaust air at that. i tried sanding the inner pump housing smooth, new impeller, new gaskets from the bottom housing up, remember i never took the bottom pump housing off until i replaced the entire thing and fixed the issue. long story short, check everything, i never thought i would have to remove the lower pump housing, it looked great.
and mine would'nt pump well on muffs either, threw it in a pail, and she was a fire hose.

 

[zbhover]

Re: 50HP Merc not pumping water, replaced impeller now what???

Re: 50HP Merc not pumping water, replaced impeller now what???

We were testing it in a 45 gallon tote, and it wasn't working so thought maybe it wasn't enough water so we took the boat down to the lake and tried it and it still didn't work.


We also tried throttling the engine up and that didn't help either........ We could blow air both up the copper tube from the bottom of the outboard, and from through the hose on the tell tale.....


jeffdjpeat I read through that thead, and maybe we have the same thing going on??? The housing looked to be just fine but who knows.................. I seen you mentioned a seal on the copper tube going into the pump housing............

On this 77' 40hp there wasn't a seal. The copper tube just goes directly in the housing........... I don't know if this is how its supposed to be or not???? It was working fine last season, maybe the rubber seal on the copper tube just fell apart and got flushed out if there is supposed to be one?????????


btw our s/n is 4707302 if that helps with finding some drawings???????


Thanks again guys!!!

 

[James P]

Re: 50HP Merc not pumping water, replaced impeller now what???

Re: 50HP Merc not pumping water, replaced impeller now what???

The impellar is inside a housing. Then there is a plate below the impellar. This plate has to be smooth for the impellar to work properly. A sandy environment will certainly groove this plate. You might also try the weedeater line down the tell tale to make sure it's not clogged. Sorry about your problems. I've been there!

 

[AEROCOOK]

Re: 50HP Merc not pumping water, replaced impeller now what???

Re: 50HP Merc not pumping water, replaced impeller now what???

We were testing it in a 45 gallon tote, and it wasn't working so thought maybe it wasn't enough water so we took the boat down to the lake and tried it and it still didn't work.


We also tried throttling the engine up and that didn't help either........ We could blow air both up the copper tube from the bottom of the outboard, and from through the hose on the tell tale.....


jeffdjpeat I read through that thead, and maybe we have the same thing going on??? The housing looked to be just fine but who knows.................. I seen you mentioned a seal on the copper tube going into the pump housing............

On this 77' 40hp there wasn't a seal. The copper tube just goes directly in the housing........... I don't know if this is how its supposed to be or not???? It was working fine last season, maybe the rubber seal on the copper tube just fell apart and got flushed out if there is supposed to be one?????????


btw our s/n is 4707302 if that helps with finding some drawings???????


Thanks again guys!!!

I believe there should be a seal between the water pump body and the water tube, at least thats what I see in the parts schematic diagram. This could definately cause low water pressure if it were missing.

 

[zbhover]

Re: 50HP Merc not pumping water, Missing gaskets/seals???

Re: 50HP Merc not pumping water, Missing gaskets/seals???

Alright I found what I believe to be the breakdown of the lower unit on the 1977 merc 50hp sn 4704302.

I don't have any gaskets or seals where the water tube goes into pump housing so maybe thats our problem??? Or atleast part of the problem.

I found the drawing with part #'s here:
http://www.sterndrive.info/mercury-outboard-parts/40hp_70hp_drawings.html

Its looking like I'm missing parts #1 and #2, the OEM #'s for those are:
OEM # 26-38452
and
OEM # 12-38453


Does this seem correct to you guys??? I'd just hate to order the wrong parts and then have to wait for the right ones to come in..........



THANKS again guys!!!


bye

 

[zbhover]

Re: 50HP Merc not pumping water, Missing seals or Gaskets???

Does any one know if parts #1 and #2 look like the parts I'll need in the link I posted in my last post???

The link is:
http://www.sterndrive.info/mercury-o..._drawings.html



THANKS!!!

 

[This_lil_fishy]

Re: 50HP Merc not pumping water, Missing seals or Gaskets???

Same LU as me. The drawing is a bit deceptive. The rubber seal and nylon washer go into the bottom of the top housing, not the top as drawn. If you push the copper tube through it will push the nylon washer out, and sometimes the rubber seal. If those are missing out of the top housing then you will need to replace them. Should come with the gasket kit I'd think. Still waiting for mine to come in to know for sure.

The tube should fit snuggly into the pump housing, if it is just sitting there loose there is no way it could pump water up through the motor.

Ian

 

[AEROCOOK]

Re: 50HP Merc not pumping water, Missing seals or Gaskets???

Same LU as me. The drawing is a bit deceptive. The rubber seal and nylon washer go into the bottom of the top housing, not the top as drawn. If you push the copper tube through it will push the nylon washer out, and sometimes the rubber seal. If those are missing out of the top housing then you will need to replace them. Should come with the gasket kit I'd think. Still waiting for mine to come in to know for sure.

The tube should fit snuggly into the pump housing, if it is just sitting there loose there is no way it could pump water up through the motor.

Ian

Yes, This_lil_fishy is correct, the drawing is deceptive. I thought I was missing the same parts for mine when I looked at the diagram. I went and bought the parts and couldnt figure out how to install them. Then I discovered that they fit into place from the inside, not on the outside as the picture suggests. I now have spare parts since I discovered that mine werent missing after all.
By the way, I replaced a Merc water pump on the weekend for a nephew and noticed one of the impellor blades was missing, did a back flush hoping to find the missing piece of rubber but nothing came out. I ended up finding it behind the plastic water pickup vent.
zbhover, have you removed the water pickup vents on yours to inspect for obstructions?