1973 4hp Evinrude

[film495]

I got some feedback on another forum vintage section, the white spots on the electrode are likely detonation or preignition. They are egging me on to install a knock sensor, but I'm not sure I'm that advanced mechanically, so - maybe I'll just use this as an excuse to pick up a timing light.

I got some colder plugs, I run B8S NGK in another one, and those plugs that have run for a couple years now, look happy and a nice brown, no fouling, both plugs look exactly the same, put them back in. Usually, that motor just gets pinned open, and we just ride around the islands, up and down the lake, nothing like a little boat, for the sake of a boat ride.

I could run more oil, or mess with what octane the fuel is, but I'll likely stick to 24:1 if I'm testing motors and regular 87 Octane pump fuel.

This motor was over heating before and I got the water pump going good, so - apparently the water pump was likely working perfectly good already and the overheating is from another reason.

 

[racerone]

I do not believe a " knock sensor " can be fitted on a 1973 4 HP !!!-----Who are these clowns suggesting that ?

 

[film495]

thanks for reading or commenting, this motor was a project so far for sure. I just want to practice working on one, and this one has been good for that.

can anyone recommend a timing light that works on these well? can you rig a battery and bulb to these? for static timing, can I just put a battery and bulb in a circuit, positive to the spark plug lead and then ground to frame? will the points opening and closing dim and bright the bulb? seems like something I could experiment with when I have a flywheel off to get at all the leads and see if I have to remove the ground from the coil, so - it tries to ground through the points.

you know, I gotta admit - I really like gaining more and more of an understanding of how these points ignitions work. 15 years or so ago, I paid a mechanic to do an ignition on the old 68 3hp Evinrude, and I was like - uuhhh, what's a points? I did an old Ariens S-12 with a single cylinder Kohler 12hp motor, first points. Just one point... lol

Do they make a small engine outboard that is a single cylinder or are they all twins and up? I'm just cracking up at the idea of idling down a single cylinder thumper on the back of a small rowboat.

 

[racerone]

There are numerous videos on how to set the points ( timing ) using the timing marks and an ohmmeter.----There is a timing tool that can be used.----A factory / shop time saver.----But you can use the timing marks on the flywheel and magneto plate as well.-----Learn about the timing on these simple magnetos.-----You will be glad you did.----Will take away all the guess work process that so many folks use.

 

[film495]

I do not believe a " knock sensor " can be fitted on a 1973 4 HP !!!-----Who are these clowns suggesting that ?

just some clowns on another part of the internet. they did jump right on a knock sensor, but just trying a timing light, and maybe running colder plugs, or a bit more oil in the gas, they went right to engineering a knock sensor on the fly. I'll let someone else try that if it ever happens.

They did pick out the white bits on the plugs as a problem, so - grabbing a timing light and giving it a look, seems like my path. I did pull apart a 70s twin Rotax 440 that had experienced detonation or pre ignition and it really just ate the inside of the head and it was like a marbled pitted mess.

I don't have high hopes for this motor, but hey - if I get it working and I have a couple others, you know - I might just give it to a friend of mine who's maybe been a bit down on his luck, if it ends up being a decent little runner, seems like that would be the right thing to do with it.

 

[film495]

I did check the timing with an ohm meter. It was opening just on the slow side, of the two marks. Right on the 2nd mark, but it supposed to be in the middle. My guess points a bit worn, either I'll replace them or just gap them a bit wider to adjust the timing. Motor seemed to run pretty good, last test in a bucket, not great, doesn't seem to want to idle down that well. Plugs looked more normal.

 

[film495]

Haven't had this motor back out to test. I need to pull the flywheel off another motor, and I'll probably do this one, and either put new points or open them up a hair more to .022 to see if I can get the timing to hit right in the middle. It was funny, one side had a hole in the bottom of the stator plate where the condenser screw goes, and the other side did not have that hole, not sure if someone did that or if that is how it came from the factory.

anyway, tinkering with how to use the ohm meter to check the static timing, seemed to figure out out quickly enough. I've done that on other motors with a battery and a light bulb, but the meter seems to indicate an open or closed connection well enough after fidgeting with it for a bit and getting the connections set up correctly.

 

[Crosbyman]

points gap is not to important what is important if points opening at the right instant

 

[film495]

I gave this motor an on the lake run test end of last year. It ran strong, but still eventually started to make a squealing noise like an auto belt squeal sound, and lose power and die. It did this to me on the previous test run, and I did a bunch of fixes to it, and same behavior. That was last fall. I turned it over with the pull cord this spring and it didn't fully sieze up, so - I have it a once over and reset the points gap, and checked the static timing close enough. Ran the motor for an hour or more, sounds like piston slap at slow idle, like a knock, and then at high speed, after 20 or 30 seconds it starts to lose power. If I then just run slow for a few minutes, I'll get another 20 seconds or so of full power, and rinse and repeat. I finished the day doing this exercize. I had satisfied myself, that I got this motor to work and run, so - it seemed to operate fine for a good 1/2 hour, at medium throttle, and just go like it would do that all day. Then I played with the upper throttle a bit too much, just to see what would happen, and it lost power and stopped, accompanied by a nice sqealing belt sound. This morning when I checked the plugs, one of them did have some small white spots, that could indicate detonation, or lean running etc. Oh, I also ran 93 Octane gas, and put a colder set of plugs in it. I guess now that I've probably damaged it I should probably take the time to compression test it.

Anyway. Fun run. Just to actually just run this motor for a while today. I did a little tune up on another one, and it ran better too, but not quite right.

 

[film495]

compression test today - 4hp 1974 Evinrude Yachtwin
top 107, bottom 99

when I got the motor last year the test results I got were 100, 95

The spark plugs looked decent to me. I took a few pictures

 

[film495]

top plug on right, these look pretty decent to me, but what do I know? One of them appeared to have little white specs on it from the last run, so - I assumed detonation or overheating. I ran it for about 1.5 hours on the lake. It seemed to run fine at mid/low throttle, I was able to just go around, no issued running like that. At higher RPMs it, looses power after say 30 seconds, slowly loses power, I can just run it slower for a while, and then it will run full strenth again. and on and on. Too much fast speed running and eventually it will stall out, and that is what happened on the last run, and these are those plugs.

 

[racerone]

Have you checked the water pump impeller ?----Checked fuel pump diaphragm?---=-A 5o year old pump might benefit from a new diaphragm.-----Yes , just the new diaphragm is available all day long.

 

[film495]

When it stalled, I cupped water in my had and poured it over the head and spark plugs expecting it to steam, and it didn't. also, the compression numbers point to the piston not seizing, so - I could not make a guess as to why it stalled.

It starts a bit hard, but not too bad, and it super difficult to restart once warm. Pulling the plugs and letting the motor cool for 10 minutes seems to work fine, but it does not seem over heated. I can handle the plugs by hand.

knocking - probably piston slap at low RPMs.

I grabbed this motor to mess with, and I have a 71 Johnson 4hp, I could try to run, but the flywheel nut, well, the threaded end of the shaft the nut goes onto is broken off, so - the flywheel nut can only be theaded about 1/2 way on, and I don't want to run a motor like that.

In theory I could just break them down, and take the shaft out of this 73 4hp Evinrude, and put it in the 71 Johnson 4hp.

 

[film495]

Have you checked the water pump impeller ?----Checked fuel pump diaphragm?---=-A 5o year old pump might benefit from a new diaphragm.-----Yes , just the new diaphragm is available all day long.

I did the water pump on this motor last year, and it seems to be working correctly. I put a new fuel pump in it last year as well.

 

[film495]

If I had to guess I never got the head to seal correctly, and at higher temps it leaks more, and affects running. The exhaust gasket I suspect leaks a bit too, but I don't think that would affect running particularly if it is a relatively small leak. Some water collects at the base, and I suspect it is from the water jacket that is under the plate and gaset there. I'm not sure I care to mess with that anytime soon or the head, as I have a couple of these going good, but next time I mess with this I'll probably just see about setting up a good timing light for it, so when I do points I can narrow down the timing. I always thought really nailing down the timing on any motor was fun. Expecially an old points motor. I can then use the same set up on the other ones, just to fine tune them a little more.

 

[racerone]

Every outboard cylinder head I have taken off was warped !-----They should be refinished before installing a new head gasket.

 

[Crosbyman]

you don't need a fancy timing light to service a 4hp. Just set points at .020 with the cam lobe's high point or use the voltmeter test.

Yet .020 isn't all the t important was is .. is that point open at EXACTLY TDC
the VOM will tell you or a simple LED or bulb on a battery will tell you when points open...

 

[racerone]

Using a timing light / meter to set the points is the best way to set points.----Points open at the time when voltage / current is at the maximum and get the highest voltage at the sparkplugs.-----Strong spark makes for 1 or 2 pull starting !