1973 4hp Evinrude

F

film495

Petty Officer 1st Class
Joined
Apr 8, 2009
Messages
285
racerone said:
I don't think so !
Click to expand...
no idea. found a few old threads where it comes up, here's one. they didn't work through and find a conclusion on it.

1972 Johnson 4HP - No Spark

I recently purchased a 1972 Johnson 4HP for a very good price. Seller told me it would not start. Compression on both cylinders is appx 92 psig. Solid. The problem I am having is that when I pull the starter I get no spark on either cylinder. I hooked up an adjustable gap tester and see...
forums.iboats.com forums.iboats.com
 
C

Crosbyman

Vice Admiral
Joined
Nov 5, 2006
Messages
5,410
Film495 ...

we have all been answering lots of questions concerns, theories, suspicions on a 4hp. No offense but it may be time for serious reading, utube watching if you realy want this simple 4hp to work for you. Maybe it is a lemon.
 
F

film495

Petty Officer 1st Class
Joined
Apr 8, 2009
Messages
285
I'll have to find time to test it to be sure, but if nobody knows what that ground strap is supposed to do, or how to install it, I think I've figured it out.

It definitely connects/grounds the armature/magneto plate, to the armature support ring which is grounded to the frame. So, that ground strap grounds the armature plate to the frame. How and why and what the function of this is, will have to test it and observe.
 
R

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
37,722
Picture / part# / exact location of this ---" ground strap "---Would help you.
 
C

cyclops222

Lieutenant Junior Grade
Joined
Mar 21, 2024
Messages
1,233
IT may be a magnetic field collapsing strap. They speed up the response of a wire wound magnetic field.
 
C

Crosbyman

Vice Admiral
Joined
Nov 5, 2006
Messages
5,410
yes nonsense... if you do have some form of grounding strap & yes I have seen on other otboards magplate underside it would only serve to help the return of the HV spikes to the plugs themselves returning to refeerence ground on the frame. The mag plate grounded or not it never enough away from engine frame ground since it sits and rotates on the "grounded" crankshaft and a few thousands of inches would not stop 10-15Kvolts from returning to the coil grounded on one primary wire.

nothing to do with killing the engine. ....just do so by choking it like done on several oldies.

you are making all this very complicated as you learn how these things work. Just clean the carb fix the electricals and if compression is ok that kicker should work... if not just dump it.


post you picture to clarify the issue...post to a file sharing site and post the link with general access so we can all see what exactly you are talking aboutso we don'T reach post #100 before getting it purr like it should. .

millions of these 3-4-5 7.5 9.5 10 15 hp and up magnetos work fine.
 
Last edited:
R

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
37,722
And the 1.5 / 2 / 6 / 18 / 20 / 25 / 28 / 30 / 33 / 35 / 40 HP all used this simple magneto from about 1950 to 1990.-----An elegantly simple unit.
 
F

film495

Petty Officer 1st Class
Joined
Apr 8, 2009
Messages
285

part #26, yea - it just rides on the support plate, you have to kind of angle it correctly, when tightening the clamp for the plug wire that it shares a bolt with when routing new plug wires.

I pulled the ignition to go over it again, and test coils and condensers. All came back good far as I can tell. Reinstalled, set gaps again, jumps a good 1/4inch gap on a test plug. While I had it apart I put new plug wires in it.

I took the head off to see about flipping it, so the spark plug wires don't get caught in the hood latch, and point them to the right. The head did not seem to want at all to be attached this way, couldn't get the bolts to all thread, not sure if that is by design or an artifact of the head having been warped. I don't think I got a good seal, appeared to me that the very bottom may have been leaking. Makes sense since that is the hardest part to clean the surfaces good, so - I was going to redo that anyways, and we'll see if it holds on a 2nd try after I collect a couple more head gaskets // good reminder, just ordered those.

I pulled the steering tube, pretty easy, just cleaned it and greased it and put it back. The lower dampener is ovaled a bit, but if it runs good I guess I'll worry about it then.

So, on this guy, I gotta wait on a carb kit, and now a head gasket, before I can button it up and run it in a bucket again. Getting the head gasket to seal might be the bane of this things existance.
 
F

film495

Petty Officer 1st Class
Joined
Apr 8, 2009
Messages
285
ran good. I got impatient and just cut a high temp paper gasket. good enough for a test run. I'll check the head again for leaking when I swap it. There's a couple gouges in the head, and a nick/chunk out of one of the corners, those may prevent a good seal.

I forgot to take a picture of it. oh, maybe it is in one of the pics from earlier in the thread, when the head was identified as being warped. The bottom cylinder outside edge where the water channel is, the compressible flat is lessened, and that is where it was leaking.

Went back and looked. You can't see that piece of the cylinder block in the pic, but the gasket looks like it was leaking between cylinders, not at the bottom, so - that is positive thinking that there is hope....lol
 
C

Crosbyman

Vice Admiral
Joined
Nov 5, 2006
Messages
5,410
pictures don't work (post) here anymore. gouges can be filled with JB weld
and sanded smooth like metal. the gasket will protect it when installed properly
 
F

film495

Petty Officer 1st Class
Joined
Apr 8, 2009
Messages
285
got a proper gasket. the hand cut one looked like it sealed decent when I took it off. I pulled the flywheel and used a piece of glass to resurface the cylinder block a little bit, cleaned it all up and installed fresh head gasket.

ran in a bucket for a while, seemed pretty good. doesn't idle down like a 3hp, but it idles. It kind of falls off quick when you try to idle it down too far, I'll have to run it for a while and check the plugs.

Other than retorque the head bolts now that it has been run, I think it is ready for a water test ,whenever I can actually get to the water to test it out.
 
F

film495

Petty Officer 1st Class
Joined
Apr 8, 2009
Messages
285
I got this motor out and on a 14 foot aluminum, seemed to run decent, weird, but decent. started hard, just too many pulls to be normal, but it starts eventually. Got it started, had to dial the jets a bit, and then it really came up to speed. I would say running properly, changing speeds, up and down the throttle, doesn't idle real low, but OK. After about 2 minutes it lost RPM, but like 30%, and ran there for a few minutes, I throttle down to like 1/3 throttle, and it ran fine there for several minutes. After a bit, I opened up the throttle again, and it came right up to speed, seemed like correct RPM, really pushing us along very well, and after a couple minutes, same thing, just dropped RPM, and ran at about 70% power. I've never seen that before. If I had to guess maybe overheating, but it didn't conk out, it just lost power at high RPM, and then later after running at a lower throttle like 1/3 throttle, then it would run up at full speed again, but only for 2 or 3 minutes. Seemed like a repeatable behavior, but other than overheating I can't really put a guess at it, and it seems to be pumping and pushing water really well.
 
F

film495

Petty Officer 1st Class
Joined
Apr 8, 2009
Messages
285
a bit of research, says this might be a fuel problem. it didn't act like I've seen with loose gas line fittings or sucking air, maybe a pickup tube in the tank. fuel pump is new. I have a chance to test the tank on a couple motors this weekend, and go over it in more detail if needed.
 
F

film495

Petty Officer 1st Class
Joined
Apr 8, 2009
Messages
285
I tested the tank on another motor, so - rules that out. Not sure when I'll get to run this again. I'll probably clean the carb and check the head to see if I find any signs of leaking, and run it again.
 
F

film495

Petty Officer 1st Class
Joined
Apr 8, 2009
Messages
285
tested tank on other motors works fine
fuel pump is new
tested same carb on another motor runs fine

I had hoped this was a fuel system problem, cause that would be easy. I think I'll finish cleaning up another 4hp Carb, and put it on and think about running this again. Maybe I'll just put new condensers in it first, just cause it is easy and that just fixed another motor I've been tinkering on.
 
F

film495

Petty Officer 1st Class
Joined
Apr 8, 2009
Messages
285
What is the preferred way to test for blown crank seals without a pressure test set up. Can I just spray carb cleaner in a couple particular spots, and it would become apparent?

Just a general question on these things that I wondered about. These motors make a little sluge ring on the inside of the hood, that lines up just right with the flywheel. I've seen like the same sludgy residue under hoods on 70s two stroke Rotax motors. The exhaust on the Rotax motors isn't very tight, so I always figured it was just from the exhaust. On these, what is that indicative of, is that an exhaust leak? crank seal? run it?
 
F

film495

Petty Officer 1st Class
Joined
Apr 8, 2009
Messages
285
trying to share some plug pics. top cylinder on right, bottom on left, these are new plugs, they did some test runs, and then about a 10 minute ride around a pond Champion j6c.



 
Last edited:
You must log in or register to reply here.
Top