48 SPL idle issues. Throttle cam, idle orifice,

[mikeyk101]

I am in the process of doing a bunch of preventive maintainance on my 87 Johnson 48 SPL. I am a boating newbie and slowly learning my way. I bought my first boat last summer and found that it had a problem with idling but ran great underway and at wot. But the idling was driving me crazy. I am now familiar with link and sync and also have an OMC service manual. I finally dived into it to start tackling the problem. I discovered that the throttle cam roller was missing the outside sleeve which I suspected and already had a new replacement. In the process of getting the o ring off to replace it, the o ring self destructed. It had hardened and pretty much fell apart so I will be replacing that shortly. Took the carbs apart and there was no gunk whatsoever in there but since I had them apart and had the rebuild kits, I went ahead and replaced just about everything. About the only thing I saw not quite right was the float on the bottom carb opened up way too much. Also, I had picked up a screwdriver from McMaster-Carr that had been mentioned elsewhere to remove the idle air bleed orifice and high speed orifice. It worked out rather well. But I did notice that whoever had taken these carbs apart previously had damaged the slot for the idle air bleed orifices.

So first question, would the damaged slot in the idle air bleed orifices require that I put new ones in there or should they be ok?

As I get further into this, I have a question on the throttle cam plate that the throttle cam roller meets up with. It seems to have some slop and besides rolling back and forth like it should, it has quite a bit of wiggling . I did search but couldn't find any info it. I didnt want to try and tighten it down without knowing. How much free play should that throttle cam have? Should I be trying to tighten the mounting bolt to take out the wiggle?

And last year, when I did my first attempts at link and sink, I discovered that the timing linkage that goes somewhere under the flywheel was extremely sluggish and doesnt move very well. I'm assuming the flywheel will need to come off to handle this? I do have the A-144 holder but surprisingly I dont have the 1-5/16 nut on the flywheel. My 1-1/8 seems to fit it very well. From reading I thought it was supposed to be 1-5/16. Do I have the wrong nut on there? And any tips on what to look for to fix the sluggish timing likage?

Sorry for the long winded post. I'm trying to get all the details in. And I'm sure as I go further into project, I will probably have more questions...

 

[racerone]

The 1-5/16" socket is used on 3 and 4 cylinder motors.

 

[Faztbullet]

What kind of idling problem did you have????

 

[mikeyk101]

What kind of idling problem did you have????

It seemed like an erratic idle and would only idle for a short time before the engine died. It seemed like the idle was set too low. I could get it to stay running by pushing throttle forward a bit in neutral but then when I wanted to get it in gear, I had to do it quick before rpm's dropped to much or it would die again. And sometimes it ended up slamming into gear which I know is bad. Out on the lake, I could work through that but loading onto the trailer at the end of the day was a real pain. Like I mentioned above, after doing a bunch of reading, I dicovered the sleeve on the cam roller was gone so that would have been a big issue. And the o ring holding that on was hardened and fell apart when removing. Also some of the gas lines I have noticed are in so-so shape and many probably should be replaced.

And I recently picked up a tach that I should have had last year and didnt. I'm sure that will help out with diagnosing the problem this time around.

The boat is kept in Wisconsin and the weather hasnt been really conducive to doing much. I only get up there on the occasional weekend now so I haven't had a lot of time to dive into it until recently. I have it in a garage now but only have a small propane heater and that limits ambit on what I can do. It needs a good going over as I dont know the history of it. It was an oily mess in there with quite a bit of debris. It does seem like the previous owner did some work to it, I'm guessing, to try and fix the issue as there were some new parts in there. The coils were fairly clean unlike a lot of the rest of the components. And the carbs seemed like they had been rebuilt not too long ago as they were actually pretty clean in there but one float was misadjusted and dropped too far.

If the slots on the idle air bleed orifice were nicked up a bit, how bad is that? Should they be replaced? Not sure who did it but that was what I found in there.

And how much play should there be on the throttle cam? The throttle cam is attached by a rod to another rotating piece towards the back. The other part is on solid and has no wiggle and rotates like I think it should but the throttle cam has quite a bit of wiggle besides its rotating. I dont know if this is normal or maybe the bushing needs to be replaced?

 

[racerone]

The first thing to do in trouble shooting is a compression test.----Post the results of a test here.

 

[mikeyk101]

It ran out of time this trip up so it may be a week or so before I can get back to it to do a compression test. I already have a compression tester and actually knew I should be doing that but dived into a bunch of other stuff on this first... I will do that as soon as I am able and let you know. Thanks.

 

[mikeyk101]

Just to add, this motor seems like it has been neglected for some time and have already found a bunch of stuff that has needed to be replaced. Since I have limited time for now to get up there to do the work, I try to order the parts I need beforehand. I will do the compression test as I agree that is important but would also like to be ready with the other stuff that I am fairly certain needs attention as well. Can anyone tell me if I need to replace the idle air bleed orifices that have nicked up slots and what about the slop I have found in the throttle cam plate? Does it need a new bushing or is some slop normal?

 

[mikeyk101]

Ok, curiosity got the best of me so I had a few spare minutes. I hooked up the battery to do a compression test. On a cold engine (no way to really warm it up right now...) top cylinder was just over 100 psi and lower cylinder was right around 90 psi. I would say that seems decent? The plugs that I replaced last year looked good, tan in color, and not fouled.

 

[racerone]

Your opinion may vary.------I would not be encouraged by those compression numbers !-----An inspection is in order I say.----If nothing is wrong a new head gasket is CHEAP.

 

[mikeyk101]

Ok, I will look further on this the next time I get back to it. Thanks.

 

[mikeyk101]

Just for clarification, I also did the compression test with the carbs removed. Would this have any impact on the compression results?

 

[racerone]

Makes no difference----None whatsoever.----A different gauge could be tried.

 

[juno pierrat]

yep compression is low, but try another gauge if you can, I have the same engine with compression around 145 on both cylinders. i'd remove head for inspection, no scoring or gouges in cylinder walls let us know what you find. anyway when ordering parts get new thermostat and water cover gasket, because changing the thermostat while head is still on the engine is a PITA. now let it be said, removing the head my lead to broken bolts, especially on a saltwater motor, oops, your in frozen north

 

[mikeyk101]

This is all great advice and I understand that probably the most important thing is diagnosing the possibly low compression. I will be checking this as soon as I am able. But I am still looking for answers to the slop in the throttle cam and the nicks in the idle air bleed orifices.

Is there normally wiggling on that throttle cam besides the normal back and forth rotation? There is absolutely nothing in the service manual. My hunch is that this isnt normal but after searching everywhere, I can not find any answers.

And if someone used wrong screwdriver on those orifices and slightly gouged the orifice slots, can I continue to use them and they will work fine or do they need to be replaced? They will still go in and out fine but not sure if the gouges/nicks will affect their function. Either way, if I will still need this information as well.

 

[Faztbullet]

Damaged slots on jets wot hurt it.

 

[juno pierrat]

yes, there is a little play in the bolt that holds the cam, i think the bolt has a collar/sleeve, when tightened it hits the block and wont let you over tighten the cam plate to a point were it won't move/rotate. i would go look but rainy, cold and under a tarp. also looking at parts diagram, there is a plastic bushing that goes around the bolt and in the cam bolt hole, maybe that is missing like the cam roller. also ill let you know the flywheel net size tomorrow. the timing linkage is probably ok it the engine doesn't bog when accelerating to cruise speed.

 

[mikeyk101]

Thank you gentleman. That's more info that I can use. Dont worry on bolt size. I confirmed earlier in post that it's not a 1-5/16 like I originally thought. The 1-1/8 did the trick for me. Thanks again. I will update as I find out more on the compression...

 

[juno pierrat]

if you've got a 1 1/16, could be a better fit, but it sounds like you might have the nut off already

 

[mikeyk101]

An update... Looks like the compression tester wasnt sealing properly when I used it last and that's why Inwas getting the mediocre cylinder pressures.. It had a fitting on it for 14mm but the oring was falling apart. I took that fitting off to bring with and get a new oring. I discovered that the threads where the fitting fits on were also 14mm and then stepped up to 18mm. After getting a new oring, I tried it on the main part and screwed that into the cylinder head. I had picked up a remote start switch and connected that to the starter solenoid. I hooked up a freshly charged battery and pushed on the starter switch. After a couple seconds, I saw the compression tester quickly rise and this time both cylinders tested at 150 psi! Fantastic! One less thing I have to look into.

 

[mikeyk101]

Another update... I finally everything back together last weekend and got a chance to fire it up. I was able to pump up the bulb and it stays hard. I tried the key, turned it to run, pushed it in for 8 seconds to prime, and then turned it to start, and nothing. I then pulled out my remote start switch, hooked it up at the solenoid, left the key on run, turned the red primer lever all the way back, and pushed the remote start switch and it cranked a few times but finally fired up. Actually ran pretty good. Since I am also redoing the dash and haven't put it back on, I was able to pull the tachometer which is plugged into the optional harness by the ignition switch all the way to the back of the boat but discovered it wasnt working. I turned the key off and back to run again began checking the terminals on the back of the tach. I was surprised when I was getting -12.52 when checking the ground and switched positive. I pulled back the cover on the optional harness and discovered that the switched positive wire and ground were opposite to the connector it was plugged into. That was an easy fix as I had the amphenol tools and swapped the wires in the optional harness. Again I tried the ignition switch to start the motor and nothing. I then started the motor via the remote starter switch and the motor again started and I could see the tach was now working. Progress! I then went back to the starter switch and began unscrewing each connector individually and cleaning each one. After finishing, I tried the ignition switch and this timeI could hear the primer clicking and when I turned it to start, I could get it to crank a bit but it seemed like it only engaged the starter for a second or two before the starter gear would drop down from the flywheel. It's as if not enough power is being provided to the starter. When I use the remote starter switch, I can tell that full power is being applied and the starter gear remains engaged with the flywheel until I let go of switch. I have a little more trouble shooting to do and think it may either be a faulty ignition switch or an issue with the solenoid. I ended up having to abandon the project as I had been out in the garage all day and the wife was pissed because she said I was ignoring her... I will be back up there next weekend to do some more troubleshooting as I still need to do a full link and sync now that I know it is well on the way to being a good running motor.