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1956 7520 Evinrude 7.5HP Impeller questions

D

DarrenJH

Member
Hello everyone.
This is my first post, and I would like to add that I have searched the entire Evinrude sections for the answer, But I cant find anything about it.
I am trying to get the gear housing off to access the Impeller. I removed all the screws on the bottom and it is loose, and about 1/2" away from the leg. But that is as far as I can get it.
Im guessing that the shift linkage is holding it all together but I dont have a clue on how to unhook it.
Or if I even have to unhook anything.
I replaced the Carb and plugs.
Ive bypassed the original fuel tank delivery system and added an inline prime bulb.
So I now have the engine running and it sounds great! First time in over 20 years.
But its not pumping water.
So this is where it sits now.
1956 7520 Fleetwin 7.5HP Evinrude.
Thanks for any help.
 
Thank you for the reply.
Dont worry about checking your book, I figured it out!
You are right, I had to remove the powerhead and that gave me access to the top of the shift linkage. I removed the 2 3/8" nuts and she came out.
My impeller is in one piece, so Iam happy about that.
 
pressure test it before you put it back together.The gasket under the water pump base did not hold air when installed dry on mine,but Kim is right you might want to reseal the whole lower.
 
If the impeller is in one piece, what does it look like? Maybe a finger is reversed because somebody turned the motor counter clockwise? If it has been replaced before, then maybe the old impeller broke apart and a piece is stuck somewhere where it was overlooked downstream of the pump. This unit should be pressure tested and while the pressure is on, be sure to move the shift rod up and down because sometimes that shift rod 0-ring will leak in only a certain position. Did the last guy that had it apart put silicone on the power head base gasket? Maybe the supply hole is restricted. Make sure everything is clear and open upstream of the pump too. Sometimes a motor will run good with decent compression, but if a head gasket is starting to leak compression across to the water jacket then this can disturb water flow by pressurizing the water jacket with combustion gas. I always do a compression test very first thing on these, especially if they still have the original head gasket.
 
Ok I'd like to add that this motor has only ever been in my family since new. My great grandfather purchased it new. Gave it to my grandfather. I spoke to him today and he confirmed it hasn't been started for just over 30 years!
nothing on this motor has ever been taken apart until I got it. Impeller looked brand new. Coated with oil. Gear box oil was almost clear. Cylinders had oil in them. Etc.
i put it all back together and she runs like a top.
When it wasn't pumping water... I didn't realize I didn't have it submerged enough. So I pulled out the rain barrel and used that. Brought the water up about 4" past the plate on the side And she pumps like a dream.
I've got 2 props for it. Both look great.
Its getting the real test on Friday. So hopefully everything goes well. Thanks for all the suggestions and tips.
 
Yes, I sold a guy a 9.5 Evinrude once and he lived 75 miles away. I warranty my used motors for 1 full year. The guy calls and said that the water pump quit working. I felt terrible, I couldn't figure out what could be wrong over the phone. He had a plastic drum behind the boat with the motor submerged, but his water was too low and the pump couldn't get primed up. I drove 150 miles for nothing......the guy felt pretty stupid.
 
I don't feel too bad about it. I had to take everything off and check to be sure anyway. But I'm happy I didn't have to buy a new one. I checked the gear oil and no water. So it's all sealed up. I took the motor out yesterday and wow. She runs like a dream! I'm going to play with the adjustments a little more next weekend. But I'm very happy with the first run on water in 30 years. I picked up a 7514, so I've got a lot of spare parts now. Hopefully I won't need them.

Again, thanks for all the tips, I do appreciate them!
 
Yes good job, I have several early 5.5, 7.5, and 10's. Love 'em and they will run almost forever. Now that you have started running it again, if it still has the original head gasket, keep a close eye on it because it will eventually fail. New gaskets are available from your local auto parts store through Sierra marine parts.....about $15. Okay, take care Darren.
 
Thanks for the help and hopefully there's an answer for my next questions.
So same engine. After having the motor out a few times last year. I noticed that I would loose power. I had my gps out with me and at full power when things were going good. I topped at 12km/h. Then after a while of running full tilt, the engine would just slow down. Not bog, or sputter. Just loose power. When this happened I was at about 8-9km/h.
So I started to dig in a little more. I pulled the flywheel off and found the coils coating was broken into bits. So I put in two new ones. Put everything back together today. Now I haven't had it out on the water as its ice, but in the barrel, after letting the engine warm up a fair bit. It lost power. Just wasn't running like it was when cold. So is that going to be caused by the condensers? I've pretty well changed everything. I haven't messed with the reeds or anything internal. Good news is there is a local dealer that has a soft spot for old motors and is extremely helpful in helping me get parts. Only problem is they are not much older than I and don't know too much about these old beauts.
And my next question, I have a parts breakdown and notice an oil transfer tube. I haven't put any oil in. Or found a place to add oil. Or even seen a post about this. Do I need to put oil in for the bearings? Or is it supposed to be unserviceable bearings?
Thanks for any help in advance.
And I gotta tell you, I can't help but smile ear to ear when she's humming down the lake. The looks and comments I get are unreal. Having something so old, being used as it was intended in its glory days is out of this world. I know this doesn't mean much to a lot. But I know some of you know how I feel being able to use this piece passed down from my great grandfather.
 
You are running it with a 24:1 oil mix I hope. If not it sounds like you may have a good parts motor. Do a compression test and like was said the old head gasket may need to be replaced. Real easy to do.
 
Oil is recycled from the bottom of the engine to the top.----------Most 2 strokes use a tube / hose / passage way for that.
 
I am running 24:1.
I have a head gasket coming, should be here today.
I will do a pressure test today.
I refuse to accept the option of this being a parts motor.
As for the oil tube. I understand what it's for. But I would imagine it may require new oil after this long. Is there any type or any way to go about putting new oil in?
 
The engine is allways recycling the oil that settles in the crankcase to the upper bearing. There is a check valve on one of the fittings that only allows flow in one direction. It is possible the check valve is not working but not likely.
 
Looking closer at the older 7.5 it looks like the metal tube was pressed into the crankcase both top and bottom without a check valve. I wouldnt worry about it pull the head and inspect the cylinder walls for scoring. Resurface the head on a glass table with 220 grit paper in a figure 8 pattern until it all shines the same then slowly torque it down to spec in at least three steps using a center out bolt pattern.
60-84 inch lbs torque for the head bolts
 
BTW the reason for 24:1 mix is those old motors dont have roller bearings in the connecting rods same with the mains dont have ball bearings either.
 
Good to know.
Alright so I did a compression test. Seems low. But I don't know what it should be. I've got 66psi top cylinder and 68psi bottom cylinder. That was at hot and cold tests.
 
When it looses power can you stop the motor and does it turn over with the starter rope with more drag? Then once it cools down does it turn over with normal effort? This would mean another issue like overheating or lack of lubrication. The condensers would not cause the problem you have described, and I still suspect a head gasket that is failing.....if it is still the original. Love these old motors I run them and I TRUST them. I repair newer outboards too and they are not perfect either. Good luck, careful removing the head bolts. Wire brush them, blow out the threaded holes in the block, run tap in if needed, surface head on a perfectly flat surface with some wet/dry sandpaper.....using water. Finalize with a figure 8 pattern and about 240 grit. Clean deposits off pistons and combustion chamber.....leaving no scratches. Torque head with the threads LIGHTLY coated with anti seize. Put a tiny dab on the head surface of each bolt hole where the bolt hex contacts there. Use a torque sequence from the central bolts to the outer bolts and bring torque up in small intervals. Anti seize plug threads lightly too. When head is off, clean and vacuum or blow any debris out of cooling passages.......do it right and it will last a lifetime. Be sure to use only non oxy fuel and I recommend Amsoil 100:1 pre mix but mixed at 50:1. I will get blasted by my piers here. But I have done this for 40 years in the older bushing motors without a single failure. I would not substitute any other synthetic at this ratio. I have only run Amsoil. On the larger hp motors that are run wide open most of the time, I run @ 40:1. If anything turns out to be major problem with your motor, talk to me and I can set you up with parts.......got lots of these around.
 
Compression test is a bit low but that depends on how fast you pulled it too. Should build to max compression in 6 fast hard pulls. Gauges vary too and compression generally goes up as horsepower ratings increase. Just checked a 1984 9.9 Evinrude that I bought yesterday at the Pawn America and it ran 90 and 95 with a borrowed gauge from O'Reilly Auto Parts. My gauge at home would only produce 80 and 85. So....lesson learned......know your gauge.
 
Seems to feel the same. If there is a difference, I can't tell. I've got the head off now. Walls look really good. The lower piston top is coated in black residue and the top one looks pretty clean. I'll try and get pics up if it will help.
 
Put the new head gasket on and then do a good decarb once your sure it is firing on both cylinders. While it is ideling do a cylinder drop test. Pull a plug wire and put it back on while running. Use a good pair of pliers so you dont get bit. The motor should respond the same on each cylinder. if the engine stalls swap the plugs and see if it follows the plug.
70psi on a pull start motor is still serviceable.
 
So my head gasket is not in yet. I'm in Canada and it's coming from America. So I'll have to wait a bit. In the mean time, I'll use this time to clean up the head face really well. Thanks for all the help again, I'll post back when my gasket makes it in. And I'll try those tests then.
 
I hope you realize that the earlier comment about it being a parts motor was in response to your asking about where to put the oil. If you had been running it without oil in the gas, it certainly would be a parts motor by now. But all is ok on that front, so not to worry. BTW, the motor actually pumps oil from the bottom bearing up to the top one through that tube. A clever and very simple oil pump consisting of a slot in the crankshaft and ports in the bearing. Amazing how well stuff can work so well and be so simple.
 
Thats the beauty of great engineering, for me its hard to let go of it. The fastest and highest flying aircraft in the world is the SR71 and it was built in 1963, 1964. It could well be one of the greatest engineering marvels in aviation history. Our modern engineering has too often been focused on making things to wear out and/or requiring future maintenance and expensive repair costs. Creature comforts are fun but my trucks have "crank up" windows and I don't have to put on the brake in order to get it out of park........I can SEE the spark plugs when I open the hood, and the government can't shut me down from a satellite. No thank you, brother. KIS.....keep it simple.
 
Alright.
So I got my head gasket in today. Im in the process of cleaning up the head faces.
I replaced the condensers anyway as they were pretty cheap and the shop had them in stock.
Ive got some pictures of the cylinders and the unit itself.
Ill check compression again as soon as I get things back together.
motor 2.jpgmotor 3.jpgmotor 4.jpgmotor 5.jpgmotor 6.jpgmotor 7.jpg
 
She looks nice, I don't see much of a problem with the head gasket, at least on the block side. That is not to say that something could have been leaking a bit on the head side. The cylinders look good and normally a bit richer or darker color on the lower cylinder. The overall condition of the motor seems very good by the photos. Let us know how things progress. Regards, Tim
 
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