3.9hp no bowel movement

[apollothesun]

Hey there boaters,
ive been a lurker for several months and have enjoyed all the threads in this forum. now im looking to see if some of you guru's can help me out.
i bought a mercury 1967 3.9hp and i noticed that when i first fired it up, there was almost like a constant spit out the water tell tale hole. figuring it needed a water impellar i went ahead and bought and replaced it. well after 10 times of putting it together it still overheats and now there's not even a spit coming out.
is there some secret or something im missing? im able to shift forward, nuetral or reverse just fine. i torqued the waterpump down as per specs but nothing. ive shot compressed air every where water should be coming out. i filled the bucket at certain water heights to no success. one thing i noticed is that the piece that connects the waterpump to the brass pipe is a little loose. meaning connecting to the brass pipe that leads up to cool the engine isnt snug, it fits over the pipe loosely. in the parts manual there is no special washer or anything that im missing to tell me it should be snug. when i first dropped the lower unit, the connection piece simply fell off.
please give me any insight if any of you all ran accross my situation.
my next resort is to probably pull the powerhead and see what im missing.
thanks in advance.

 

[Ross72]

Re: 3.9hp no bowel movement

I don't know if this will help or not but there are 2 different impellers for that motor depending on the year. Don't ask how I figured it out, let's just say I used the wrong one. Anyhow, the older style of impeller does not use a key to hold it in. There is a pin that fits in the drive shaft and the slot in the impeller is less than 1/4". This impeller is for the '65 through (I think) mid '66 motors.

The second impeller has the complete key way slot. If you use the one with the full slot and don't have the key way, you will shred the impeller in about 2 seconds.

 

[apollothesun]

Re: 3.9hp no bowel movement

hey Ross72, thanks for your reply

im glad i have a place to go to for advice and such. it feels fustrating at the garage lately. i dont know what i got myself into but i got into this hobby after my wife said i need to quit growing saltwater corals and let the family enjoy more of my free time. she advised boating but realized how much more this is addicting. im really fustrated on this and kinda bummed not able to figure this out. this is my first project in many more projects i have invested my time into. but lets get back to the deliemma...

You are correct about the keyway and slot pin. i ordered the sierra replacement part and the keyway ran straight down but the original impellar, the keyway ran only halfway. im figuring if the pin catches the keyway, it wouldnt matter as long as it catches and spins right?

could this be the reason why its not working?

i noticed also the new impellar although the same size and shape as the older one, when i put the water pump together and torque it i can feel tension in there while turning the shaft. like the impellar is to big for the water pump.

i took the last couple days to ponder the impellar water pump.
so as the powerhead is spinning, it in turns spins the impellar and pumps water up the sleeve guide impellar tube up the water inlet tube. the water is now inside the baffle of the exhaust manifold and exits circulating through the walls of the housing of the piston and spark plug area. it now enters back into the exhaust manifold baffle and exits into the exhaust relief out of the bottom cowl and finally the pee hole. so the pressure of the combustion of the pistons smoke should push the water out back into the bottom cowl where water should exit. i get great exhaust smoke but no water.

ive tried hand tightening the exhaust manifold and see water running through there and escapes through the small openings on the gasket, but when i torque to spec, no water out the pee hole.

do you think the sleeve guide inlet tube needs to be more secure meaning tight fit so as to not loosing any pressure as the water is being sent up the inlet cooling tube?
when reassembling the lower unit, the inlet tube just fits over the cooling tube.


im really bummed i cant get the simple project going.
anybody else have any situations or suggestions?
waterless in seattle

 

[apollothesun]

Re: 3.9hp no bowel movement

one thing i noticed too is that before i dissambled i tried shooting compressed air up the inlet tube at the bottom of the lower unit and can feel air escaping the pee hole. now when i do it i dont feel the air at the pee hole.

 

[apollothesun]

Re: 3.9hp no bowel movement

upon looking at the parts diagram, does the drive shaft gasket, bottom cowl to drive shaft housing be clogged? or does the water even go through that gasket?

 

[saumon]

Re: 3.9hp no bowel movement

Try blowing air backward (into the peehole and exit through the water tube). Pieces of shredded impeller or whatever you want may have been pushed up the cooling passages...

 

[Ross72]

Re: 3.9hp no bowel movement

That is exactly what happened when I changed mine. I put the full slot impeller in when it should have been the half slot one. The impeller is determined by SERIAL number NOT model number. That is how I found this out at my local dealer, he had it on the shelf. Also, I if remember correctly, when I installed the first (wrong) impeller everything seemed a little tight.

I agree with saumon about blowing air through the opposite way, there is probably some impeller chunks in there.

When it is running properly, water will start shouting out the pee hole after 5 to 10 seconds on initial start up. There should be a very noticable stream coming out.

Hope this helps, I know it was a real pain when it happened to me.

 

[apollothesun]

Re: 3.9hp no bowel movement

thanks Ross72 for your insight and experience. you are a valuable patron to this community.
thanks saumon for your suggestion, i appreciate your help.

well i got home, fed the kids, spent family time with the wife watching american idol and told her the reason why this motors not working is because of the wrong impellar and she rolled her eyes talking about more money and the other boat im supposed to be working on. i told her got to get to the garage just 40 minutes. i gotta love my wife for her understanding, patience and sarcasm.
so,
went to the garage, changed the new impellar to the old one and noticed how more smoothly it now turns. wow, thanks Ross72, you saved me hours of troubleshooting and banging hammers on my workbench. man that gear selector rod is sure tricky getting put back together. well 45 minutes later im ready to fire her up.
okay, here we go,
still no water out of the pee hole. man, that was disheartening.
i noticed alot of bubbles coming out of the midsection and the lower unit. so i pulled her out and retorqued the midsection and lower unit. i grabbed the compressed air and shot it in the inlet pipe down below. its now blowing out of the pee hole. yeah! it blew some exhaust fumes in the process. i blew some compressed air down the pee hole and was coming out below.
i added more water to the garbage test can also.
went to fire her up but still no water out of the pee hole. aarrggghh!
bubbles were still coming out of the midsection and lower unit. what's causing the bubbles to come out there?
i know the new impellar didnt do that. the old impellar has all its fins but a little brittle. could the old impellar be the reason why its not pushing water up the inlet tube?
well and hour and half later i had to quit because it was 11pm and didnt want to upset the neighbors.
still need some of the iboat insight guys..
i will start looking for an impellar serial number on the iboat store.
regards
apollo

 

[Ross72]

Re: 3.9hp no bowel movement

On the underside of the cavatation plate there should be a metal screen about the size of a quarter. Remove the screen and clean it out well. This is your intake and mine was clogged enough to only let a very small amount of water in.

Apollo, did you put the old impeller back in? When I took my old one out, it looked ok but was a little brittle but was not pumping any water. Also, check to see that you have a good seal where the water tube enters the water pump housing.

The last thing thar I can think of is use a piece of welding wire (mig) or some wire with similiar guage and run it through the pee hole just in case there is some thing lodged in there.

Don't give up, your almost there and you will be impressed how well that little motor runs.

 

[apollothesun]

Re: 3.9hp no bowel movement

Hey Ross72,
yeah last night i used the old impellar.
well today after work i headed to a mercury dealer and got the oem impellar.

got it hooked up, and no water again through the pee hole and still running into bubbles coming out of the lower unit and mid section.
i tore it apart again and tried wire up the delivery hole, nothing evident.
question about making the seal from the water pump to the water tube. theres that yellow tube that connects the water pump to the brass pipe that leads up to the engine. now the water pump to the yellow tube is nice and tight. the yellow pipe to the brass pipe basically fits easily. do i need to make that tight? what did you do to do that?
regards
apollo

 

[ONERCBOATER]

Re: 3.9hp no bowel movement

ok if i understand this right....when you shoot air up the tube that the water is supposed to go (after the water pump) you get air out of the pee hole? correct? and when you shoot air up the pee hole with the engine not running and the water pump off you can feel air coming out of the water pump tube?
if yes, then i would suggest putting engine on stand so that it is as it would be on boat....upright, and applying water to the waterline that the waterpump feeds... you should get water out of the pee hole then....if not than at least you know it isn't likely to be the water pump that is the issue....
sometimes calcification, and corrosion can allow air through in enough volume that it appears free flowing but slow water to almost the stopping point.

Sean

 

[Ross72]

Re: 3.9hp no bowel movement

Apollo,

My water tube fit relatively snuggly into the water pump. What is the condition of the metal plate that the inpeller sits on top of? Is it scratched badly or grooved at all? If so, it could be preventing the pump housing from making a proper seal. I believe that there is an o-ring in there, check it's condition and replace if suspect.

It appears that everything is put together correctly from what you describe. When you describe air bubbles coming out of the lower unit is it where the 2 sections meet? If so, is there so noticeable dmage where some one pryed them apart? It could be preventing the parts from mating properly if there is a burr. I don't think this has anything to do with it, but just one thing to check.

OK, here's what I would do next. Since you are now a master of removing the lower unit, I would take it off. Next hook a water hose directly to the water tube. If water comes out the pee hole, the problem is probably a seal (gasket/o-ring) in the pump housing, if not you have a clog in your water passages.

Your getting closer, narrowing down the possibilities.

 

[apollothesun]

Re: 3.9hp no bowel movement

hey guys, just got back from the garage. i have put another 5 hours of trying to get this thing going.

onercboater thanks for the suggestion. when i was at the garage earlier around 6pm after fiddling with it for a couple hours, i was gonna do what you suggested. great minds think alike!

hey ross72 thanks for sticking with me. thanks for helping a owner with owner experience.
with the metal plate that sits on the impeller, there are no groves or scratch marks of any kind. the only o-ring i can think of that your talking about is where you connect the bottom of the water pump to seal the fluid for the lower unit oil. when i took it apart, there was no o-ring inside the water pump. the oem parts list doesnt show one there. if you need a parts list heres the link
http://www.boats.net/parts/search/M...EAR HOUSING (DRIVE SHAFT) (PAGE 1)/parts.html

there is no damage between the upper housing to the lower unit when i disassemble them. basically they slid out the first time of many times.

so, i disassembled for the 10th time , when i pumped water into the lower end tubing up, i get water coming down the upper housing unit like its not routing to the pee hole.
when i pump water to the pee hole its doing the same thing in spilling out the the upper housing, not appearing at the lower unit tubing.

i disassemble the exhaust manifold on the side of the powerhead to see why the water is not routing to the lower unit or to the pee hole. when i shoot compressed air up from the lower unit tubing i can feel where the air where it enters the manifold. so i shooted air everywhere where there were holes inside the manifold. when i was shooting air at this particular hole, i noticed that it shoots out back to the inside of the upper housing. its the hole beneath the water entering hole.
observing this im basically thinking that the water travels through the passage ways of the manifold, in and around the the engine and exiting up here back inside the upper housing. is this how the water travels and should that be correct?
when i shoot air through the pee hole, i dont feel air around the exhaust manifold but feeling air in the upper unit housing.
this logic means the water travels all around the passage ways and then ends up inside the upper housing and combustion exhaust pushes out the water out into the pee hole. correct?
im i missing something here as in parts in the upper housing thats not routing the water to the pee hole? looking at the oem parts list, there are no tubes or connection that im missing to tell me im missing a part.

im thinking that ending hole at the exhaust manifold that leads to the upper housing is causing back pressure in the water pump causing air to rise instead of water and exiting the joining of the upper and lower end.

well, my head hurts.
regards
apollo

 

[saumon]

Re: 3.9hp no bowel movement

observing this im basically thinking that the water travels through the passage ways of the manifold, in and around the the engine and exiting up here back inside the upper housing. is this how the water travels and should that be correct?
when i shoot air through the pee hole, i dont feel air around the exhaust manifold but feeling air in the upper unit housing.
this logic means the water travels all around the passage ways and then ends up inside the upper housing and combustion exhaust pushes out the water out into the pee hole. correct?

Not right. Exiting water souldn't be dumped in the housing but routed around the block then through the peehole. Something is missing in your engine. Is the water tube sealed properly? #15 here http://www.boats.net/parts/search/M...98135/DRIVE SHAFT HOUSING ASSEMBLY/parts.html

 

[Ross72]

Re: 3.9hp no bowel movement

I agree with saumon, something is not right. Right now, my motor is 2 hours away at the cottage. I'm at a loss, is there supposed to a grommet on the top of the water tube where it fits into the block? That is the only other thing that I can think of without having the motor here in front of me. Sorry, I'm pretty much out of ideas.

 

[bktheking]

Re: 3.9hp no bowel movement

Had this happen with a bigger merc in the summer, 7.5 I believe. Check that the rubber seal is in tact where the pickup tube goes from the pump to the water intake screen in the gearcase and check the one that goes into the pump housing. If that tube seal is gone it will never pump, I made a seal out of a briggs and stratton fuel grommet, fit perfect. It has to be tight or the system won't pump right, trust me.

I believe there is a bushing assembly to which that water tube goes into, could be shot but I doubt it.

 

[apollothesun]

Re: 3.9hp no bowel movement

Just chiming in guys. thanks saumon, ross72 and bktheking for the suggestions. i got tired of not seeing areas where my ground wire was poking so i took apart last night. powerhead, midsection and lower unit. there was some blockage. i will post pics tonight after getting to the garage tonight.

 

[apollothesun]

Re: 3.9hp no bowel movement







heres a couple pics where the blockages are seen with the pick tool.
the last pick is where the pic is seen going through the exhaust manifold and enters the upper unit before the water is pushed out the by exhaust at the pee hole. that is correct in understanding how water gets to the pee hole right?

 

[bktheking]

Re: 3.9hp no bowel movement

Is there an actual telltale on this motor or is it just the exhaust type. Was there a tube coming off the powerhead? I know my 6 hp has the tellale at the back and no actual tube, my 4 hp just has exhaust holes.

 

[apollothesun]

Re: 3.9hp no bowel movement

Is there an actual telltale on this motor or is it just the exhaust type. Was there a tube coming off the powerhead? I know my 6 hp has the tellale at the back and no actual tube, my 4 hp just has exhaust holes.

thanks for the interest bktheking. i took a couple more pictures before i put it all back together in regards about the tell tale hole.





the first pic is the tell tale hole.
the second pic is above shot of where water would enter the tell tale hole.
the third pic is where water enters the tell tale hole as pointed out by the pic tool

im firing her up tonight after work. im praying water comes out of the hole.

one thing i noticed when i dismantled the lower unit to the powerhead was the copper tubing was not bent correctly to make a good seal. i bent it where it would make a secure connection from the water pump to the seal of the powerhead. i noticed while cleaning up around the holes there was hard crud that wouldnt let water pass through the passages more freely. im hoping this does the trick. wish me luck!
apollo