1973 Johnson 135hp Ignition / Tachometer Issues

Hi:

I am new to boats and outboard motors. I remember boating and skiing with my dad back in the day and I always thought boats were super cool. I don't know why it took me so long to get one of my own and go with my kids. In my mind they stopped making awesome boats in the 90's (not long after they stopped making good country music), so I really want to make this old boat run right. Late in the summer I picked up an sweet little 15.5' ski boat from the same vintage as the '73 Johnson 135hp which I purchased separately and installed on the boat.

I figure (and others whom I talk to as well) this boat should seriously rip. With a 19p prop, it gets out of the hole so-so okay and tops out at a gps'd 42 mph. I would guess that's the top speed for that prop. However, only with careful weight shifting can I barely get on plane with a 21p prop, then I can't get to any good RPM and it tops out at around 35mph. I should say I'm at 4000', but I figure the beauty glitter paint this boats' got should cancel that out as far as performance goes. Determining the RPMs has been difficult. See below.

What I know:

1.) Compression is 110psi on 3 cylinders, 103 or so on one of the cylinders. The side with the lower compression does seem to run a bit hotter, but not too hot: 59deg C if I remember right, 50degC on the 'good' side. I took the head off the side of concern and observed a small bit of damage on the head of the piston. Kinda looked like something solid went through the engine.

2.) I think the engine mounting is good. 1 hole up. This put the cavitation plate level with the bottom of the boat.

3.) Carbs are clean. I even picked up a ultrasonic cleaner for the job. Turns out I didn't need it though, they came apart nice and everything was good anyway, I figure the previous owner was in there not too long ago and did the same thing. I did notice that the sea level orifices were in there. The manual says it's good for 0-3000' and I'm at 4000'. I ordered the higher elevation orifices but have yet to install them. I think I have bigger problems.

4.) She starts and idles beauty.

5.) The rectifier tested bad. I replaced it. See below.

Here are my observations / things I don't understand / problems:

1.) All the plugs are black, greasy / kinda wet carbon caked. They are new and they are the non adjustable gap type. Maybe the higher elevation jets will help with this?

2.) This thing uses a TON of fuel. After a run on the lake I observed raw fuel sitting in the cowling near the airbox. This makes me think I have a bigger problem then just low elevation jets.

3.) The fuel issue made me wonder if I wasn't sparking right so I did a spark gap test for each of the cylinders. Set for 7/16 gap. They did good although 1 cylinder had a more yellow spark than blue.

4.) The rectifier tested bad. I replaced it later. I think it blew right away on hooking the battery back up. Again, see below.

So from the performance so far and these observation I figured that this engine can perform much better and be more reasonable in it's fuel consumption. I figured that I need a tach to be able to determine where I'm at when testing and get some answers. It only raised more questions. Here's what I did:

1.) I picked up a new Faria 0-7000 RPM tach. Hooked it up. For power to the tach and tach backlight I used keyed power from the remote. I connected the grey 'signal' wire from the remote as well. Ground to battery.

2.) The tach has a dial that can be set from 1-6. The instructions that came with the tach are undecipherable to me. Long story short is that I am unable to figure out how many poles this engine has or what setting that would equate to anyway. But: there is only 6 settings and none of them are accurate through the RPM range. I know this because I had to set the dial to 4 to have a reasonably close reading at idle ~1100RPM, I would too high for sure, but it was the closest I could get. At WOT with that 19p prop, I was getting ~6700RPM: too high, by ear I can reasonable say it wasn't crazy over-reving like that.

3.) In order to be able to get an accurate RPM reading I got a little creative. I picked up two tachs of different styles. The first an induction style tach that has a wire that wraps around the spark plug wire. By induction it counts sparks and infers RPM. I also picked up an optical tach. This thing I like. I stick a piece of reflective tape on the flywheel and the optical sensor directly measures flywheel RPM. Sweet.

4.) I was concerned about things like inductive interference with the inductive tach so I tested each spark plug wire and moved and jiggled it in every position possible. From this tach I suspect it might not be the most accurate, but I did notice it is pretty damn consistent in it's measurement. By this I mean that no matter what I did to move and screw around with an individual cylinder spark plug, it read that cylinder the same no matter what. This includes me changing out the coil on one of them.

Aside: I tested these tachs on my snowmobile. All three were pretty much bang on 1700RPM (sled tach, induction meter, and optical meter looking at primary clutch).

5.) The results: Flywheel by optical: 700 RPM. Induction measured at each cylinder: 420 RPM, 840 RPM, 900 RPM, 1050 RPM. This is a crazy result for at least two reasons. Why the inconsistency between cylinders? How can two of the cylinders be higher then the actual RPM from the optical meter ( I would say the optical meter is indisputable)?

6.)I pulled the flywheel and inspected the stator and base timer. Both looked good. Oddly, I observed some of that sticky brown stator juice on the engine but the stator looked totally good. I think it might have been replaced by the original owner. I did an ohm check on the stator leads but not knowing what the reading were supposed to be all I can say is that they were some number of ohms but not shorted out between any leads (I think I'm telling the truth, as I'm going by memory, if this is critical knowledge I can pull the stator and give concrete numbers). I was also disappointed that a stator test was not laid out in the service manual. I have to say that service manual totally sucks.

7.)From the RPM results I figured that if different funny electrical things are happening between different cylinders, the power pack must be to blame. So I replaced it, I replaced the rectifier at the same time. But like I said earlier I think I blew it as soon as I hooked up the battery.

8.)With everything back together (and at the time unaware of my rectifier issue continuing) I put 'er on the muffs and repeated my RPM test. Same results. Like exact same results.

Commenting on the rectifier: I think it was on this forum that I read that a rectifier will not fix a spark problem. Period. I think I agree with that statement. Can a bad rectifier wreck a power pack or stator which in turn can cause a spark problem? I'm not so sure about that.

I realize the extreme length of this question/story. I figure more detail the better. Please let me know your thoughts.

The damage on the one piston tells me it has broken rings there.-----Remove cover on the SIDE of that suspect cylinder to inspect piston / rings.----Post a picture of what you see.----I think this motor has to come apart.-----Note that boat motor combo should run at 50 / 55 MPH if in good condition !

You were right. Busted ring. I guess i need to ask myself if it’s worth a rebuild.

See that failure all the time !----If you can do the work yourself it might be worth it.----Few shops will do that kind of work today.----Your location ?

Too late now, but FYI, the tach should be set at 6 pulses/rev

Northern Alberta. I think Mott's Machining in Edmonton would do it.

I've been up all night thinking about my options, no sleep. Another long story short, I do have a 74' Johnson 115hp as well sitting on a stand. Thing is that one also it's share of problems. It has good compression, but I know the previous owner cooked it pretty good. He told me so. I dug into it a bit and found the water impellor to be destroyed, but on top of that, I took the thermostat assemble apart and found the vernatherm and all the plastic little valves to be totally melted, the passages at the assemble were blocked.

So, I figure I have two sets of problems to choose from:

1.) The 73 135: Full on engine rebuild. These outboard motors are crazy, my understanding is that the only way to do rings is to pull piston out of the bottom of the engine. But even if I do it, I still have this very odd electrical problem. Or do I even have a problem there? I don't know anymore. I did check that newly replaced rectifier and it is blown. What's with that? So this comes down to at least one big job and some cash with no guarantees in the end. But if it works I'm gonna have a major butt kicker of a boat.

2.) The 74 115: Not excited about an engine with less rock n roll, but I bet she will be no slouch. This one might turn into a brand new rabbit hole. I will definitely be checking the rings on that one, no guarantees there. Provided the rings are good, I could swap thermostat assemblies from the 135 for nothing. It has a bad rectifier too, and stator juice, and some melted wires around the powerpack.

With all my rectifier issues, can you confirm for me the testing procedure:

1.)Remove Rectifier from engine
2.)For this 3 wire rectifier. Connect an ohmmeter from the red lead to each of the yellow leads. Each reading should be about .5Mohm
3.)Reverse the leads. Each reading should be open circuit.

I'm getting about .5Mohm in one direction, and 5 and 15 Mohm is the other direction. I tested it before installing it and it was as it should have been.

I will think on this some more. One way or another I'm going boating (next year). In the meantime I would appreciate anyone's thoughts or experiences like these.

The 73 model V-4 engines are ---UNIQUE----No internal engine parts from 72 will fit.-----No internal parts from 74 will fit either.-----AND no the piston does not pull out the bottom either.-----I am in Ontario.----Have lots of parts for the 73 model V-4 motors.

You can replace the rectifier in either of those engines with an RMstator rectifier/regulator.
It fits in the same spot as the normal rectifier and has the same form factor but adds
regulation to your previously unregulated charging circuit. I did this on my E115TLCIM
and it has been working well so far.

You really need to think carefully about rebuilding your 1973 model 135 HP.-----If you have to pay a shop $100/ hr + tax it will add up.------Likely find a much newer motor for less coins.----You have till MAY to shop / look for one.-------What lake are you running in at 4000' elevation ?

Your retifier test is only half complete. You should check both directions between each yellow and red and also both directions between each yellow and ground. Each test should show a high resistance in one directon and low resistance in the other direction. If you are using a digital multimeter, forget it unless it has a diode test function.

Thanks everyone for your help. So the 115 also has bigger problems. Some major scoring on one of the pistons. If there is one thing I learned in the last couple days, it's that side port is super useful in Johnson engine diagnosis. Man!.

I'm in the Hinton area and have Jarvis Lake 15 minutes away and I can get to Rock Lake in about an hour. Grande Cache also has Victor Lake which is a super nice lake too. For Alberta lakes these are definitely among the best. But they are all mountain fed lakes so they are a bit on the cold side.

A bunch of your comments are interesting:

Racerone:
You don't have to pull the pistons from the bottom? I thought the basic procedure for any sort of top end work on an outboard is to 1.)Pull the powerhead. 2) Split the crankcase open. 3.) Disconnect the connecting rod from the crank. 4.) Pull piston out of the bottom of the cylinder 5.) Fix cylinder / piston. I watched a youtube video of a guy pulling apart an old Mercury and frankly it scared the crap out of me. All that for a ring. FML. These are definitely not snowmobile engines. But whatever, I'm thinking I want to do this rebuild. If I do it myself I'm hoping it will be cheap enough. Besides the tear down experience is pure gold and the cost of that is free. I should only need a shop to bore the cylinders and If I serve it up to them ready to go, I'm hoping it wouldn't cost me too much would it? I doubt the cylinders are nicasiled.

Finding parts for the 73' does appear to be pretty tough. Do you have a line on some or are you in the parts business? I can't even find a gasket kit.

James is Canada:
Thanks for the Rectifier advice. If needed I will pick one of those up.

fdrgator:
Interesting. Thanks, I did not know this. Nor have I ever used the diode function of my multimeter. My multimeter does have a diode function. It outputs in Volts. I'm guessing that it's telling me the voltage drop to break over the diode? Anyway, for all 4 tests it gave me open circuit in one direction and ~.5 V in the other. Maybe the rectifier is fine. With the engine off my fully charged battery showed 13 volts. When running it gave me 13.2V.

Thanks again everyone for your replies.

Your understanding of the tear-own is basically correct, except for the direction the pistons come out of the cylinder. They come out of the top (cylinder head) end. But even so, the case has to be split to remove the rods from the crank. Yep, many (most) old Mercuries have blind cylinders with no head, and the pistons come out the crank end of the cylinders. That kind sure is a pain to reassemble without the proper ring compressors. Your Johnson can be assembled with your fingers, however the sleeve-type ring compressors make it So-o-o much easier.

You should be looking at videos of Johnson outboard repairs.------Don't forget to add inspection / reseal of the lower unit to the list of things to do.-----Cylinder sleeves are just cast iron and cast in place.-----Hope to visit many Alberta / BC lakes with an ----Action marine 17---- in the future.------evinrudeparts.ca----Is one place where you will get help with parts.

Find O/S pistons before spending any coins on the 73 model 135 HP.

Hi Everyone:

Again, I can't thank you all enough for the help you've given me. I feel like I'm on the right path again.

So here's my plan: Call me crazy but I think I can fix this 135 up for less than 200 bucks. All I need is a gasket set, rings, time, and luck. On looking at that bad piston, the cylinder looks totally fine so I think there is a real chance that the jugs and pistons are all good. I will post my progress, and probably more questions.

I doubt you can re-use that one piston !----As I said I have seen lots of this damage before.-----Fixed the first one of these back in about 1981 / 82 or so.----But good luck with the project.

Thanks for the heads up. I will let you know for sure.

Hello Again Everyone:

So I got the whole engine apart 100%. I have to say it came apart wicked easy. The whole time I was thinking that somebody was recently in this engine. Turns out, from the part numbers stamped on the pistons, they are all .030" O/S. I believe that is the max. Not a big deal since I don't think I would be willing to pay for, or even source all the required parts that such a job would require. So here is what I found:

From the attached pictures, I think we would all agree that the piston with the thrown rings needs to be replaced. That is findable part. What I'm wondering is opinions on whether a little bit of careful emery cloth on that nicked exhaust port and a full hone job will be 'totally fine man!' or closer to: 'I don't know man, I think it's gonna blow up right away!'. One thought I had is that that nick is at the bottom of the exhaust port so it shouldn't have any sort of effect of the pressure profile of the running piston.

In taking apart the engine, there is one thing I did not understand. These bolts on the inner ring of the crank head assembly. They had high temp silicone on them (picture attached). Seems a bit sketchy to me. What would make a person want to do this? My best guess is that crank seal was bad, but my experience has been: bad crank seal = exploded engine, and those bolts would be way down the list of problems. I'm very confused by this and I'm wondering what it's telling me.

This engine came apart sooo easy, I am certain it's been rebuilt in the last year for sure. It looked to me that; except the thrown ring, everything was good and assembled correctly. I wonder why this engine failed so quickly after a rebuild?

Those 4 bolts go into the #4 crankcase !----Therefor they must be sealed.----Some folks do a better job of that then others.----I do not have enough fingers and toes to count how many times I have seen this damage !----On the 1998 version of that motor you will see a neat rubber seal for that screw.

Sorry, I screwed up and added one wrong picture. Here is the one I meant to add.

Ya for sure. When you put that way... I guess there is no arguing that.

They screw into that plate in the crankcase. They call it a 'Lower Bearing Plate'. I can't figure it's purpose. Edit: It must hold the bearing in place.

So is that the correct procedure? Silicone the bolts before install? There must be a better way!

???---Well that locates the bearing so that the crankshaft does not bounce up and down.----Look at the design of this motor carefully.-----See that the 98 model of this engine has the neat rubber seals ?

Yes I do. Right there. I guess that is that.

So what do you think? Will she run for another 46 years? Tell me the truth, I can take it.

Nope.-----That high lighted in yellow is the seal for the crankshaft.----Every motor has that.---------On the 1998 version of that V-4 each one of those 4 screws for the bearing retainer plate has a rubber seal , item 14A.------And it did NOT run for 46 years as it was rebuilt once already.----In Alberta not many of these motors run in January so they can last for many more years if properly rebuilt.

Oh ya, now I get it. Kinda looks like a flat looking O-ring to me.

Anyway, thanks again for the input. I will post results.

Hi.

Did I just majorly screw up? This is the block side of the crank case. I wish I would have taken a picture of this brass piece before I started chiseling it out. I don't know what it would be. My best guess is that it's from the hole right beside it. As can be seen there is more brass in that hole. I figured the crank pushed it into the side of the case like that. Is that supposed to be there? What is it? Before I started screwing with it, it just looked like a chunk of brass embedded in the side of the case.

I'm not sure how this all goes together and the parts diagram isn't telling me enough. As shown, #2 is called a dowel. I would guess that is the dowel that the crank bearing sits in.

All I am going to say that a HAMMER & CHISEL is not needed to repair one of these fine precision built motors !

Alright. I see that messed up. I do sincerely appreciate the help you've provided so far, I think it's safe to say you know your way around these engines. However, I would like remind you that I don't. I came to this forum to seek advice from experience people like yourself on a topic that I'm not to experience with. If you cannot keep you responses respectful, keep them to yourself. I don't need your help that bad.

SwervinMervin said:

I wish I would have taken a picture of this brass piece before I started chiseling it out. I don't know what it would be. My best guess is that it's from the hole right beside it. As can be seen there is more brass in that hole. I figured the crank pushed it into the side of the case like that. Is that supposed to be there? What is it? Before I started screwing with it, it just looked like a chunk of brass embedded in the side of the case.

I'm not sure how this all goes together and the parts diagram isn't telling me enough. As shown, #2 is called a dowel. I would guess that is the dowel that the crank bearing sits in.

Click to expand...

I just checked the service manual... Yes, the dowel is to keep the sleeve from turning, to keep it aligned so that the oil feed hole of the sleeve stays aligned with the other hole you're speaking of.

I don't recall if there was a brass reducer within the oil feed hole of the crankcase or not... and unfortunately, in going thru a few of the various hp service manuals, there are no pictures depicting that area up close enough for a positive viewing, and there are no bare crankcase laying around here that I can find.

I'm sure that another member will jump in here with a definite answer of whether that oil feed hole incorporates a reducer or not.

Pertaining to the hammer and chisel thing... whatever is required can at times be the mother of invention or improvising. A sledgehammer has been wished upon more than once I'm sure.

Thanks for the feedback. I also did some looking but could find nothing on the topic of this 'oil hole'. I am going to open a new thread since this one has moved a long ways from its' original topic.