Misfire

[BogMonster]

On my Johnson FastStrike 115GL 2 stroke V4.... stinky old VRO gas guzzler.

Pretty much ever since I have had it there has been a consistent problem with a misfire on 1 cylinder at low revs, always the port side one at the bottom. I've had the plugs out enough times now to be certain it is always the same cylinder, so I'm trying to get my head around why, whether I should be worried and whether there is anything I can do about it.

How does the VRO oil injection system deliver oil to these engines, is it done individually for each cylinder or what is the method of delivery? It runs perfectly under load at anything over about 2000 rpm right up to WOT 5200, but drop to idle and within 20-30 sec there will be a misfire and smoke. When you whack the throttle open it takes a few seconds to clear (only about 1-2 sec if you have been idling for a very short time but sometimes 10-15 sec if you have been idling away for 5 or 10 minutes e.g. alongside a pontoon) and then is fine again. When it is missing at idle there is significant bluish smoke.

The plug on this one cylinder is always wet (and clean, not black/sooty) when I take it out, the others are always perfect, nice healthy light tan colour. It's had 2 new sets of plugs since I have had it, and its always the same one that comes out wet. Plugs are the right type and correctly gapped, just reset them this afternoon and the 32 thou gap had opened to about 40 or so but nothing serious, all the gaps are even.

Does anybody have any ideas? I don't use the affected low speed range much but it can catch you out when you suddenly need power and it doesn't arrive - like when I was out in about a 5-6m lazy swell the other day and occasionally had to get the hell out of the way of something that looked like it had my name on it

What does worry me slightly is that it will almost always be in the "misfiring" state when shut down (idling on trailer before shutdown), and neat unburned petrol hosing down the cylinder walls is probably not a great idea for the long term health of the engine if it is sitting around for a few weeks between uses - but usually not long enough to warrant messing around with fogging oil.

I've done about 125 hours since I got the boat 2 years ago (now a bit over 400 hours on the engine) and as far as I can remember there hasn't been any significant change in the way it has behaved.

Any thoughts would be appreciated

[Nos4r2]

How clean? Tan and clean, or like a new plug?


Compression test it.

[PeterR]

A stab in the dark as there are lots of things to check and i,m sure its what Nos is about to get to the carb may need a clean as the idle jet may have a slight blockage.My post is an early morning one as we catch the ferry soon for hols in france will see how you are getting on when i get back .good luck Peter

[Chris]

Lee at Fairweather is a good man to speak to about these older V4's was always a mine of information when I had mine. I think you may find that cylinder always runs at a differnet temp to the rest (can't remember if it is higher or lower) due to the way the water goes round the cooling jacket.

Otherwise you may need to look at the CDI unit to see if that is a problem. I dont think your engine is the one with Optical ignition otherwise I would suggest cleaning the optical sensor on top of the engine or possibly replacing it.

If you do have optical ignition I have the electronic gizmo for setting the timing let me know and I can send it over for you to try out.


Chris

[BogMonster]

Clean - as in washed shiny clean with petrol, not light tan like a healthy plug should be.

Is it safe to compression test these engines in the normal way? Some engines (the V8 in my Discovery for example) apparently if you pull the plug lead off with the engine running/cranking it can fry the ECU (I know there isn't an ECU in this just wondering if there is anything I should do?)

I think it says it is optical ignition on the plastic cover I took off but I'll check later.

[Nos4r2]

Make sure you ground the plugs(that should be standard procedure for anything with electronic ignition).


A question-do you have a manual for it? Is that cylinder the one that uses the bottom conrod on the crank?

[BogMonster]

I do have a manual for it. Not with the boat (or the manual) at the moment, but yes I think from memory the port side cylinders are slightly lower than starboard side (the plug was harder to get at anyway) so that would make that cylinder the lowest of the four - why, is there a known problem?

Just thinking about it I suspect a compression test would show that cylinder to be slightly lower anyway because of the bores being washed with petrol before shutdown and the rings would not be sealing as well? I'll have to scrounge a compression test kit anyway but we should have something suitable at work.

A label on the inside of the plastic cover over the ignition system indicates that part was made in 1997 (engine and boat purchased "new" in 2000 so it might have been old stock).

I changed the HT leads yesterday just to rule them out, but they looked OK to me. I haven't tried it again in the water since that but don't think that is the problem anyway.

[Nos4r2]

Originally Posted by BogMonster

I do have a manual for it. Not with the boat (or the manual) at the moment, but yes I think from memory the port side cylinders are slightly lower than starboard side (the plug was harder to get at anyway) so that would make that cylinder the lowest of the four - why, is there a known problem?

Just thinking about it I suspect a compression test would show that cylinder to be slightly lower anyway because of the bores being washed with petrol before shutdown and the rings would not be sealing as well? I'll have to scrounge a compression test kit anyway but we should have something suitable at work.

If it's the bottom conrod, it may mean your crank end seal is leaking. It's usual for the plugs to look steam cleaned if it leaks.

it may show on a compression test-but the easiest way to tell is to drop the lower unit off,fire a load of premix into the crankcase via the carb mouth and see if it finds its way out via anything other than the exhaust tube. Make sure the plug for that cyl is out and turn it over by hand/slowly to flush anything left out before restarting it-hydraulic lock is bad news.

[BogMonster]

Originally Posted by Nos4r2

If it's the bottom conrod, it may mean your crank end seal is leaking. It's usual for the plugs to look steam cleaned if it leaks.

it may show on a compression test-but the easiest way to tell is to drop the lower unit off,fire a load of premix into the crankcase via the carb mouth and see if it finds its way out via anything other than the exhaust tube. Make sure the plug for that cyl is out and turn it over by hand/slowly to flush anything left out before restarting it-hydraulic lock is bad news.

Yikes you mean water into the cylinder? sorry don't see exactly what is leaking from where to where? I went out today for an hour or so, and it is exactly the same with the regapped plugs and new leads so no improvement there. Shame as it runs like a peach once you are off and moving with a few revs on.

It sounds like a recipe for a big job to get the bottom off an outboard that apparently was built in 1997 and probably never stripped since (no it hasn't had the impeller changed, ever, and I've been putting that off for the same reason!)

Not having anywhere to work on it under cover is a bit of a bugger too as when the weather is OK to work outside it's usually windy/dusty!

[Nos4r2]

Originally Posted by BogMonster

Yikes you mean water into the cylinder? sorry don't see exactly what is leaking from where to where? I went out today for an hour or so, and it is exactly the same with the regapped plugs and new leads so no improvement there. Shame as it runs like a peach once you are off and moving with a few revs on.

It sounds like a recipe for a big job to get the bottom off an outboard that apparently was built in 1997 and probably never stripped since (no it hasn't had the impeller changed, ever, and I've been putting that off for the same reason!)

Not having anywhere to work on it under cover is a bit of a bugger too as when the weather is OK to work outside it's usually windy/dusty!

Maybe... Does it come out of the water and get flushed every use? If not then it's probably not water in the cylinder as the plug would be rusting.

[Chris]

Stephen,

Given this problem has been consistent over the last 125 hours of use and has not worsened I would be looking at the electronics and the set up of the optical ignition.

Don't touch the carbs as they are factory set and should not need any adjustment througout the life of the engine. And I think its fair to say your VRO (which will be the version 2 VRO) is fine or you would either have black oily plugs or no engine at all!

All adjustments to the mixture & timing should be done using the optical ignition settings which effectively adjusts the timing for idle and hi speed and is the method by which you set idle mixture, RPM etc.

If you have not got one then you will need a Clymer Workshop Manual and this Optical ignition set up tool that I can send you to test out.

If you like I could pick up a manual for you from my local dealer (if you have not already got one) and send it over with the tool.

Chris

[BogMonster]

Yes it's taken out of the water and flushed every time, stored with the engine down rather than tilted, as the book says to do this in winter so the leg doesn't freeze with water in it. However it wasn't when I first got it in March 06 and she spent ~ 2 months in the water without being flushed, I am sure the fault was present then.

I think the manual I have is the genuine Johnson/Evinrude one so I will bury my face in it and no doubt come up with some more silly questions

Thanks for the help, and thanks for the offer of the tool Chris

[Nasher]

Stephen

My old 150VRO suffered with an erratic idle, I'm sure different cylinders were coming in and out.
I didn't put too much effort in to it as I knew I'd change it very soon, but things did get a lot better after I'd spent an hour cleaning up all the connections to the coils, and replaced the HT leads and caps.
It was never fantastic, and oiled up quickly at low speeds, but was always good higher up the rev range.

Nasher.

[m chappelow]

as cris said earlier on and from past experience some engines bottom cylinders seem to run cooler than the upper ones and i have had a few engines where this has happened effecting the sparking side of things on the lower one ,sometimes even swapping parts over to no avail .though on one newish johnson engine it was a plug lead that was at fault,it gave spark ok to the plug when out of the engine but not under compresson in the end think we put a hotter plug in but that was years ago ,another engine had been sprayed with the thick wax type water repelant stuff which although it kept water from the electrics dident stop saltwater from getting on the parts until it dryed then started shorting things out esecially on the bottom cylinder where it couldent be cleaned proper, we only found that out by running it in the dark ,and seeing the spark tracking allover ,

[Chris]

Originally Posted by m chappelow

we only found that out by running it in the dark ,and seeing the spark tracking allover ,

Great idea !

[BogMonster]

I have changed the plug leads so those are definitely not causing the problem as its no different with the new leads yesterday.

Maybe I'll just put up with it and buy an Etec if it goes bang though I am not sure the controller of programmes would see that as a good investment

Would you normally expect the telltale to be hot or cold on these engines? I am pretty sure mine is always cold even after some time at cruising speed, so I wonder if it might be running too cold (thermostat sticking or something) and if that cylinder is prone to problems being under-temperature might make it worse?

[Chris]

Originally Posted by BogMonster

I have changed the plug leads so those are definitely not causing the problem as its no different with the new leads yesterday.

Maybe I'll just put up with it and buy an Etec if it goes bang though I am not sure the controller of programmes would see that as a good investment

Would you normally expect the telltale to be hot or cold on these engines? I am pretty sure mine is always cold even after some time at cruising speed, so I wonder if it might be running too cold (thermostat sticking or something) and if that cylinder is prone to problems being under-temperature might make it worse?

mine always ran warm, a knackered thermostat could be a good call.

[BogMonster]

OK I will read the book of words and see what sort of open heart surgery is required to change that, I bet its in a nice easy place just like the impeller isn't

Thanks