1974 Johnson 85 H.P Hard Starting

Having some starting issues I was looking at addressing before getting onto the lake this year. I bought this boat at the end of the last season, and have found that it does not like to start at all. This is my first boat, and while I am not new to engines, I am certainly inexperienced with these older 2 strokes.

I did a compression test on this motor, the results seemed to be good, they were all within 5% at around 110 psi. This may be a little low from what I have heard, but all cylinders are at least consistent. The spark plugs are brand new, they are the correct ones and are gapped, and the coils look to be in okay shape. Once it is started, though it seems to lack a bit of power, it runs smooth from idle all the way through to WOT.

For the cold starting procedure, I use full choke, and pump the primer bulb until it is quite firm. No matter how long you crank the motor, it will not start. It also does not start if you "pump" the throttle when cranking. (old farmers' trick Ive heard works on some older motors). Eventually I give up, and remove the intake cover, and spray my bottle of premix into the carb. Depending on the day, it will either need just a little bit of this extra "liquid encouragement" to get started, or it will seem to depend on my premix bottle to run for a bit, then catch.

Further, the motor seems to take a long time to "warm up" (it will stall if gear is engaged and any sort of throttle is applied, no matter how gentle if it is not fully warm)

Finally, once the motor is shut off for fishing, etc, once you attempt to restart it, it will start right away on the first key, but if it doesn't catch (maybe 1 out of 5 times this happens) then it will rarely catch on any successive attempts, and I have to go back and remove the motor cover, intake cover, and get out the premix again.

I am just wondering what I should be looking at first, whether it be a fuel pump, carb rebuild kit, etc?

Thank you for reading my novel, and any help is appreciated!

Evan

Re: 1974 Johnson 85 H.P Hard Starting

Try removing the idle orifices and cleaning them and putting some pressurised air or cleaning fluid in there to clear out any restrictions.
These orifices are on the starboard side at the rear of the carb.
Check the washer is entact that comes out with the covering screw plug

Re: 1974 Johnson 85 H.P Hard Starting

Did you pull the airbox cover to visually check to be sure that the choke solenoid is actually fully closing the choke butterflys? You will have to occasionally choke the engine repeatedly for the first minute after starting til it warms up. Possible the thermostat (vernatherm) is stuck open and the engine is running cold. That does not make for ideal combustion. Changed the thermostat lately? If you tilt the engine up while fishing, the carbs on these early crossflows tend to leak a little fuel into the airbox. You may need to reprime the fuel hose to refill the carbs. The excess fuel in the airbox gets recirculated into the #4 cyl, so it actually gets slightly flooded. Once restarted the engine may smoke more for the first minute.

Re: 1974 Johnson 85 H.P Hard Starting

Thank you for the information on the orifices, I will look into that.

I have pulled the airbox cover (have to spray premix in to start it when its cold) and both the manual choke and the solenoid are able to fully close the valves. Considering I just recently purchased the boat, I have not looked into the thermostats at all, as far as I know they could be the originals. I will certainly look into replacements (there are two, correct?) Also, I have definitely noticed the fuel in the airbox, thank you for this information.

Re: 1974 Johnson 85 H.P Hard Starting

Only one vernatherm (thermostat) on that engine.

Re: 1974 Johnson 85 H.P Hard Starting

Since you seem to be saying that it runs ok once started and warmed up, It has to be a choking problem, or improper procedure. You need to double check that choke to make sure they are slammed tight shut.

You seem to know what you are doing, but lets go through it again. To cold start, have the motor sitting level as possible, squeeze the primer bulb till firm, lift the fast idle lever on the control, lift and hold the choke switch while cranking with the key. When it starts, release the choke. Additional "bumping the choke may be necessary to keep it running till it warms up. If you try to bring it down to slow idle before it has warmed enough, it probably will stall.

Once the motor has thoroughly warmed up, make sure it isn't idleing too slow. It shouldn't be stalling when you put it in gear after warm-up.

Now, about that choke. I'm not sure what you have there. It should have two wires going to the solenoid, a purple with white stripe, and a purple with yellow stripe. The system caused some hot-start problems on some motors, so many got re-wired to correct that. In your case, the important thing is that you have a nominal 12V on BOTH wires when you hold the choke switch WHILE CRANKING. The original set-up was 12V automatic on purple/yellow, and 12V from operator-controlled switch. Never mind all that for now, what is important is voltage on BOTH when cold starting. I believe the solenoid has to be positioned for proper spring tension also.

Carb/spark sync is also important, but let's not go there just yet.

EDIT: BTW, "pumping" the throttle may work on old cars and tractors with accelerator pumps, but it won't do a darned thing on your outboard. Won't do anything on todays cars either.

Re: 1974 Johnson 85 H.P Hard Starting

Maybe he really needs to clean the carb or carbs real good to make sure there is no obstruction he is covering up with squirting mixture into the carb to get it to start. While he said he did a compression test and it was 110 psi (which is not bad) he never said he removed and cleaned the carb(s). I'd do that first and foremost before jumping into timing and things like that. And while his thermostat could be a problem, I just don’t see how it is affecting his initial starting issue myself... And I have to wonder why he has to reprime the fuel bulb before trying to start or restart the engine each time. That is not correct by any standards...

Also, Welcome to iboats :welcome: glad to have you aboard and hope we can help or have helped you with your problem...

Re: 1974 Johnson 85 H.P Hard Starting

Firstly, thank you for the welcome, hopefully I can soon become knowledgeable enough to help people out as well. Secondly, there is a lot of good advice here, I will try to address all points as best I can.

F_R: The starting procedure you mentioned is what I tend to try to follow, however I have not yet gotten it started using that procedure. Generally when I start it I start it with the cover and airbox cover off, because I am expecting to have to use premix, I believe that the chokes are tight, however next time I go out to troubleshoot I will ensure that they are right sealed. I usually operate the manual choke, while I get somebody else to crank, so the solenoid isn't an issue at this moment. How long should I be expecting to crank it before it starts using your procedure? Usually I try several 5-15 second intervals without any luck, then resort to the premix.

It doesn't stall once I engage gear and it is warm, but it just seems like it takes an excessive amount of time to warm up, and it also seems like it needs to warm up whenever I start it, even if the engine itself has just been ran and it is certainly warm. (to clarify the stalling, it doesn't stall immediately, it will idle fine in gear, however as soon as I give it any throttle, it quits. Again, this seems to be only when not warm)

As for the solenoid, like I said I often use the manual choke, but the solenoid functions properly. I will double check that both wires have power, though, even if just for sake of mental security.

And I figured as much about the throttle pumping, I just figured that it couldn't hurt to try

gm280: I have not cleaned the carbs, I am a little concerned with messing up the linkages, but I'm sure that as long as I am careful it will be fine, and probably worth it. Should I get carb rebuild kits, or would they be fine with just a cleaning?

The thermostat was mentioned because I said that it seemed to take a long time to warm up, not because it wouldn't start under its own means.

I'm not sure that the fuel bulb has to be reprimed every time, but it is certainly not firm after it has been run, so I generally pump it just to ensure that fuel will be adequate.

Thank you for the advice and help so far!
Evan.
Note: What is the Vernatherm part number for the 74 85H.P? Or who would I go to to look at ordering one?

Re: 1974 Johnson 85 H.P Hard Starting

Vernatherm is part number 384719 (Sierra 18-3560 here at iboats)

Re: 1974 Johnson 85 H.P Hard Starting

Just to follow up on FR's first comment. Are you lifting the fast idle lever during the cold start procedure? It slightly opens the carb and also slightly advances timing to assist in starting.

Re: 1974 Johnson 85 H.P Hard Starting

I certainly am lifting the fast idle lever.

And thank you for that part number, I was wondering why my motor wasn't showing up under the "thermostats" section of the parts.

Re: 1974 Johnson 85 H.P Hard Starting

UPDATE: So, I decided to take the boat into a shop to get looked at since I won't have time to work on it until about the end of June. There are still some problems but here is what was found.
-Ignition system=good
-Cooling system=good
-Index flywheel and static test timing=good
-Fuel pump pressure=moderate but okay
-Carbs= gaskets leaking, rebuilt. Solved the no-start problem, also now the idle is actually using the idle circuit whereas before it was using the midrange.
-Lower unit=some sediment in oil, no metal. Refilled
-Decarb performed
-New L77JC4 spark plugs (I had bought NGK's that I thought matched the JC4's but apparently I had picked the wrong ones.)

The problem is that it still won't idle where it should be (approx 7-800 RPM). It will seem to idle fine for a while/bit, but will then bog and die. The mechanic advanced the idle timing to 10 degrees, and now it seems to idle good at around 11-1200 RPM. He seemed to think that there may be a cracked piston ring or a scored cylinder that is causing fuel to "pool" and eventually bog down the engine at idle, or something like that Any thoughts on this? Other than this, it seems to start and run quite well.

I can upload a before/after at-idle video if necessary or desired.

Also, he had mentioned that with this being the hydro-mechanical shifting system, it was originally designed for type "C" oil. At some point in the past, the oil had been replaced with the "regular" 80-90 weight leg oil. He said that this heavier weight oil is known to wear out the pump, and once you use the thicker oil, you must replace it with that- you cannot revert back the type "C" oil, as it is now too thin to effectively be pumped; thus, he replaced with the heavier weight gear oil.

My question is, is his line of thinking on this correct? If so, What oil should I use in the leg at this point, and what brand would you recommend? Go with the OEM?

Re: 1974 Johnson 85 H.P Hard Starting

The engine idle should be set to 650-700 rpm's when idling and in forward gear. The idle timing degrees do not make a difference, except to get it adjusted correctly to the correct idle rpm's. Perhaps between 4-6, but 10 sounds high-causing your high idle. High idle will cause premature clutch dog and gear face wear. Best to correct it. If, during carb cleaning, the idle passages were not cleaned properly, there still could be some residual dried fuel still restricting the idle passages in the upper carb body. That could be enough to cause the continuing erratic idle rpm's. Once you crack the throttle just a little, the other jets will take over and the engine may run fine through the rest of the rpm range.

Re: 1974 Johnson 85 H.P Hard Starting

That was my main concern as well, that the higher idle could damage the lower unit. Maybe I was unclear in the previous post, but I wouldn't consider the idle to be erratic, it is just set higher because of the 10* timing. The mechanic seemed to know what he was doing (hopefully is what you can expect lol) with the carb rebuild, and the engine is running well on the idle circuits, but it is not able to run for an extended period of time with lower idle timing. Is there a way to easily check for residue in these idle circuits? Before the timing was adjusted,it would seem to idle fine at these lower recommended RPMs for a bit, but would soon seem to bog down, or maybe choke itself out, and die. This is what led the mechanic to believe there was an internal issue, because he was pretty confident in the job he did on the carbs.

Re: 1974 Johnson 85 H.P Hard Starting

If the mechanic did a good job on the carbs, the engine should idle down to a normal rpm level. It is possible that you have something else going on. Have you checked spark on each plugwire after you let it idle? Always possible you may be losing spark at the lower rpm's and that's what is causing it to die out.. An inductive timing light would be able to test each plugwire while it's idling.

Re: 1974 Johnson 85 H.P Hard Starting

I have not checked spark at the lower RPM levels, I will have to try to get my hands on a timing light. In the mean time here are a couple video's might give some insight as per the issue.
As you can see briefly at the end of the video, the idle timing screw is completely turned in.
I will post the second video shortly, it is just uploading.

Thanks for the suggestions thus far!
Evan

Re: 1974 Johnson 85 H.P Hard Starting

That engine idles really well. Back to your idle rpm's. Perhaps you could clarify your idle concerns: Hopefully, your comments about idle rpm's are regarding the engine idling when it is on the boat, shifted into forward gear when it's floating normally in the lake. If you are trying to get a low idle when it's running on the trailer in the back yard-won't happen. When running on the trailer the idle rpm's will easily be 1200-1300 rpm's-that's normal. The backpressure from the lake water will siginifcantly alter (decrease) the idle rpms. Once the prop is 20" under water, idling in forward gear, the idle rpm's should drop to 650-700 rpm's.

Re: 1974 Johnson 85 H.P Hard Starting

I believe when the mechanic was trying to back the idle down, it was in a tank. But yes, I don't mind if the idle is high, I was mostly just concerned about the shifting aspect of it. I had thought about the backpressure, but then thought that on the lake at idle most of the exhaust would just come out of the two exhaust ports, rather than the hub-thru. I could easily be wrong on this, I have never paid close enough attention. Perhaps my best bet is to actually get out on the lake (the ice is almost melted) and give it a try.

Re: 1974 Johnson 85 H.P Hard Starting

The exhaust relief ports are to improve idling when the lower unit is buried deep in the water. I think your engine will function normally once you actually get it in the water.

Re: 1974 Johnson 85 H.P Hard Starting

Well that is certainly encouraging. Thanks for the advice, I will take it out and see what it's like.
Evan.