1972 40hp questions

[chris16371]

Well again, in referencing the manual I have, it talks about the water inlet on the front of the lower unit with a screen on it.
​Is that screen plugged up so no water is getting in? Unless you have muffs that are specific to that, I'm guessing you ran it in a barrel? Was the water level high enough so water could get into the inlet?

​If in fact it's not getting water to the impellor, my guess would be you might have to replace it again.. Probably wrecked it if it wasn't getting water.. Yes, even a brand new one will fail QUICKLY with no water...

​I don't know too much about the 40 hp cooling, if it has a thermostat or not etc...
so I'll leave that part to others from here.. lol...

I was using muffs but tried yesterday with a drum and still only white smoke and little dribble of oil. I made sure it was the 5 little inlet holes, I'll try to remove screen after work. I don't think it has a thermostat, couldn't find one listed on parts diagram. The impeller I took out looked almost new. Does it matter which way the impeller fins are bent? I put the new one in the same way the old came out but Idk if the old one was in there right.

 

[jbuote]

Yeah, the best way to install the impellor, is to place it on the shaft, then turn the driveshaft Clockwise while pressing the housing down over the impellor. You can lube the impellor with a lightweight oil or something.
​That aligns the vanes correctly in the housing cup. basically, impellor rotates clockwise, so vanes should bend back counter-clockwise when looking down on the LU from above..

​I've seen some posts here that say they'll flip to correct position (if backwards) when it's run, and some that say they won't always flip, so If it were me, I'd set it up right.. lol..

 

[oldboat1]

would make sure the impeller key has remained in place, and that the water tube is properly fit in the housing grommet. If you pull off the l.u., first check the function without disassembling -- can feel and hear the impeller moving with the driveshaft, turning the shaft clockwise by hand. You can also test the pumping by dunking the l.u. in a tub and turning the driveshaft with a drill.

I wouldn't worry about the direction of the impeller blades, although it's good to try to orient them correctly when installing, as stated. At higher rpms, the pump becomes a centrifugal pump.

If it's a salt water motor or run in river water (silt), you may need to remove the cylinder head and cylinder head cover, and scrape out the water passages.

 

[jimmbo]

You can't use muffs on a 72 40 hp, the main water inlet is located on the front of the exhaust snout behind the propeller. I admit there are holes in a plate above the anti-ventilation plate but they are not much good for anything. If you run it in a barrel, you need the water pump,which is about 5 inches above the AV plate, fully submerged so it gets a prime.
I'm of the conviction that the vanes will not flip unless you don't want them to, so... It is not difficult to install it correctly, use a bit of Silicone grease, of dish soap for lube.

 

[chris16371]

You can't use muffs on a 72 40 hp, the main water inlet is located on the front of the exhaust snout behind the propeller. I admit there are holes in a plate above the anti-ventilation plate but they are not much good for anything. If you run it in a barrel, you need the water pump,which is about 5 inches above the AV plate, fully submerged so it gets a prime.
I'm of the conviction that the vanes will not flip unless you don't want them to, so... It is not difficult to install it correctly, use a bit of Silicone grease, of dish soap for lube.

I didn't have time to mess with it yesterday but today I will. I didn't realize that screen on the exhaust snout was the main inlet, I'll make sure that is clear. I filled barrel over the 5 holes above AV plate, I should fill higher then?

I'm going to take lower unit off again to check everything over. If I remember correctly, looking at impeller with the housing flipped upside down the fins pointed counterclockwise so when looking from above they would be clockwise. Like I said if I remember correctly lol

 

[oldboat1]

I would run it with the water level about half way up the leg, keeping the hose running. Using a makeshift "barrel", best to mount the motor on a stand, then put the barrel under the leg (motor breaths a little less exhaust). Some run a fan to clear away exhaust. Idle or fast idle only, monitoring temps.

 

[chris16371]

I would run it with the water level about half way up the leg, keeping the hose running. Using a makeshift "barrel", best to mount the motor on a stand, then put the barrel under the leg (motor breaths a little less exhaust). Some run a fan to clear away exhaust. Idle or fast idle only, monitoring temps.

Thank you for the advice!

My manual will be here today, 4 days early thank goodness. Hopefully it will help me with any other questions that come up.

 

[jimmbo]

The water pump is located where the gearcase joins to the midsection. the water has to be at least a few inches above that to ensure priming of the pump. The way to install the impeller is to put the pin/key/roller(whatever ensures impeller rotation) on the driveshaft, install the impeller, lubricate it(dish soap, silicone grease, spit) place the pump housing on shaft, then rotate the driveshaft clockwise while pressing down on the pump housing.

 

[chris16371]

The water pump is located where the gearcase joins to the midsection. the water has to be at least a few inches above that to ensure priming of the pump. The way to install the impeller is to put the pin/key/roller(whatever ensures impeller rotation) on the driveshaft, install the impeller, lubricate it(dish soap, silicone grease, spit) place the pump housing on shaft, then rotate the driveshaft clockwise while pressing down on the pump housing.

I just got done following your install instructions and it's still not pumping water. The impeller was installed backwards so I switched it. The impeller was still in new shape.

 

[racerone]

Is the copper tube installed in the exhaust housing grommet BEFORE installing the lower unit ?

 

[chris16371]

Is the copper tube installed in the exhaust housing grommet BEFORE installing the lower unit ?

Yes it is installed correctly. I'm going to buy another impeller just in case, also any gaskets I may need. To make sure I have the direction of the impeller correct, standing above lower unit looking down at it if you could look through the housing the impeller fins would be pointing clockwise correct? I have to be doing something wrong but Idk what. The service manual is very vague for water pump repair.

Well at least I made other progress with it today. I was able to install the Sierra push to choke ignition thanks to the wiring help I received on here! Starts pretty good though I have to crank the starter a little longer than I would like. Idles perfect and I have the slow speed jet adjusted good. I didn't even realize on the inside of the hood the sticker is still there saying that the factory setting for the speed jet is 3/4 of a turn out. After I get it pumping water I think it's going to be a good motor.

 

[racerone]

The vanes should be pointing counterclock wise !!-----In my opinion these pumps are simple and hard to make a mistake on.

 

[chris16371]

The vanes should be pointing counterclock wise !!-----In my opinion these pumps are simple and hard to make a mistake on.

If you flipped over the housing it points counter clockwise, if you pretend you can look through the housing from above they are clockwise. The service manual says nothing about which way to install, just has a picture showing them pointing clockwise so I assumed that was looking down at it. Counterclockwise is how I installed the first time and when I opened it back up today some of them went to the clockwise position so that was another reason I thought clockwise was correct.

I'll pull it back off tomorrow.

 

[racerone]

I was working on outboards before your motor left the factory.!---So I know how they work !

 

[chris16371]

I was working on outboards before your motor left the factory.!---So I know how they work !

I didn't say you didn't lol. I was just saying how the manual makes it look and how the impeller flipped the wrong way when I had it installed correctly the first time making me think it was installed incorrectly. I appreciate your help.

 

[racerone]

You put impeller on the shaft.---Push housing down on impeller while turning driveshaft the way the motor turns it.--You are done with this simple instalation !----You are sure that you have the correct parts ?---Any part numbers and pictures ?

 

[chris16371]

You put impeller on the shaft.---Push housing down on impeller while turning driveshaft the way the motor turns it.--You are done with this simple instalation !----You are sure that you have the correct parts ?---Any part numbers and pictures ?

Yes I have correct parts. Impeller part #378891. No pictures. I'll send some after work, including the one from the manual that is misleading. The manual is very vague on the water pump system.

Sorry this is my first time doing this. Most of the knowledge and experience I have with anything mechanical (not just outboards) was self taught and help from forums, I don't have anyone to teach me hands on so sometimes it takes some trial and error but I learn from mistakes and push forward.

Again thank you for the help.

 

[chris16371]

Below is the gearcase diagram. Anyone know if I can remove the screen plug (16) without ruining it and how I would go about removing it?

 

[racerone]

??---Pour water in from the top and see if it comes thru the screen.

 

[oldboat1]

...and use a small brad to carefully clear any blockages in the screen.

Try this for the impeller: Seat the driveshaft in the gearcase, setting the impeller key aside. Put the wear plate down in place over the shaft. Put the impeller on the driveshaft, down a foot or so. Put the housing on the driveshaft above the impeller. Grip the impeller with your left hand. Grip the housing with your right hand. Move the housing down over the impeller, rotating the impeller clockwise into the housing. Put the impeller key in place on the driveshaft. Look under the impeller and determine where the slot is for the key. Rotate the impeller clockwise in the housing and the housing on the shaft until both the impeller and the housing align with their proper mounting locations. Slide the impeller and housing assembly down to their locations at the plate. With one hand on the top of the housing, rotate the driveshaft clockwise checking to be sure the impeller is turning with the shaft (will feel and hear it turning). Be careful not to lift the driveshaft out of the gearcase. Put the screws in the cup and tighten down in a criss cross motion. Put the O-ring in the slot on top of the driveshaft, and reassemble the lower unit.