Rough idle after short lay up, 2011 ZR409

[thomas205]

Good day to you all, perplexing technical issue on a 2011 ZR409. Boat is just shy of 700 hrs now, brackish use but Coastal Edition. I haven't been using her as regularly as usual due to COVID etc. I have been having an odd problem with an intermittent elevated idle that goes away as soon as the engine warms up, no performance loss. It sits around 850rpm before settling. This has been present for about a couple months now intermittently.

Recently the boat sat for three weeks without use and when I started her up I got a bit of rough idle again and a small puff of white smoke from the exhaust. Switched off ran her again and it passed with no issue. Assumed there was some condensate or little oil leakdown.

Second time this morning after another 3 week break and the first start was a bit ugly, chugging idle, steady but not thick white/grey smoke and didn't sound happy at all. Gauges all read fine, oil clear, coolant looks fine. I did a bit of reading and went back to it a couple hours later and it ran fine, then rough on a second start, and then settled at a slightly fast idle before all of a sudden returning to being perfect. Started 5-6 times after that and got up to temperature without missing a beat.

This evening ran the boat again on the lift and it was 100% in every regard.

I try not to let the fuel get too low ever and the FCC, in line filter etc is all under 50hrs. No ethanol in fuel here. No overheats either. Could I be looking at a faulty injector? All the problems are occurring at idle. When the engine is running fine it is absolutely 100%. I am well aware of the risk of exhaust elbow failure in salt water and have changed my exhaust elbows twice now, the current set is well within the maintenance interval. Would I be correct in saying that if it was a leaking exhaust elbow or manifold it would be an issue starting every single morning rather than after longer lay ups?

Thanks for any input, I don't have any kind of dealer assistance unfortunately.

[hal2814]

The easy stuff to look at would be spark plugs and cap and rotor. Could also just be a bad batch of gas. Beyond that, what’s your fuel pressure at the rail? Could be a fuel pump. Your injector idea also has merit.

[SilentSeven]

Is the issue always associated with cold starts? Or is it cold starts after some layup period? Sounds like the latter, correct?

What happens if you start the boat cold after it was run the prior day? Starts and runs ok?

[thomas205]

Thanks for the input. Following my original post yesterday evening I dropped the boat in this morning. Previously I have just been running it on the lift with the flush hose. It fired up from cold perfectly and ran up to temp no issue. No symptoms or oddities at all. Stopped and started 3-4 times, one session boat was running tanks empty, second one under much heavier load. Again no issue. This evening ran her again on the hose to try and repeat the error but was perfect. It seems to be an issue related to lay ups of longer than two weeks. I haven't pulled the plugs yet. Could there be something that very slowly leaks down over this longer period? I figured that most fluid leaks would recur on every hot-cold cycle and therefore every cold start? I had some fuel I was a little suspicious of during the lockdown here that went into the boat, hard to say if it has worked through by now. Since the rough running yesterday I have put 13 gallons of fresh fuel in.

[SilentSeven]

Hi to Cape Town BTW...I have some work associates based there. Know the lockdown's been tough.... :/

You've kinda hit on what I was wondering as well - some sort of issue associated with an extended park. Could be a leakdown issue of some sort...but maybe something simpler than than - any chance of a moisture issue with the electronics? Distributor and cap in particular? Stuff like that seems to run out as the engine warms up. I'd poke around on that as it's an easy start. Leakdown issues are harder, no? Maybe an injector..but those tend to leak overnight, valve seal (white smoke on startup you said??), headgasket weep (coastal edition has a pressurized closed circuit water system right...are you loosing any coolant?) or maybe those exhaust elbows aren't in quite as good of shape as you think they are..but again I might expect that overnight as well??

Funky fuel is always a chance...but I'm not sure how that only happens after a park job and not all the time. Moisture forming the tank maybe...and your fuel water trap needs to be drained?

Curious one...

[thomas205]

Yer its been a bit rough down here but numbers never really got there and we are heading into summer now so let's hope its upwards from here.

With regard to the boat, ran her this morning and this evening. Didn't miss a beat.

This ZR409 is doesn't have a distributor cap as far as I know? Just plug wires. It's not a system that I know particularly well.

I am now looking at.

- Cleaning FCC and replacing filter
- New plugs
- Getting injectors tested

I haven't noticed a coolant loss but having said that the engine takes close to 21 litres (5.5 gallons) of coolant so if it were a small leak to the exhaust side I am not sure that I would notice it. Exhaust doesn't smell of coolant particularly. I could get the oil and coolant analysed but in the past when I have lost coolant it has always been through the elbow and straight out of the exhaust. I have changed out two sets of elbows but am on my original manifolds. Wisdom on the Crusader owners forum is that manifolds are good for 20 years as they only see coolant. I would replace them all but the cost of the shipping due to weight is eye watering.

I have the pressure testing cap for my coolant bottle so maybe I should get a test kit and see if the system holds pressure.

[thomas205]

Just a little follow up, I ran the boat once, it was rough, since then fine. Fast idle on start-up but settles after 4-5 mins. Didn't run under load but I expect it would be same as before.

I managed to get new plugs, apparently the last eight in the country, changed them out this evening and boat ran fine. Engine was already warm though at this stage and past its usual fault phase. I found that all eight plugs were fouled identically, heavy black carbon deposit. I am no expert but from my reading it suggests that the boat has been running rich. I see people also suggesting sitting at idle too much causes this. I idle a fair bit due to flushing the boat after use etc but I don't think it would be enough to foul them so badly.

I am now looking at a condition that would cause the engine to run rich, either faulty ECT or possibly the O2 sensor in the flame arrestor? Having said that, given that I am running in salt, it could always be corrosion in a plug somewhere. I will check all of these tomorrow and report back. Would appreciate any input, just thinking out loud here in case anyone else has come across a similar situation.

Cheers

[SilentSeven]

Hmm. Interesting on the plugs.

Any chance to locate a service manual the describes the engine control circuit?

Looked here / don't see one /
https://www.planetnautique.com/vb5/f...uals-brochures

See this / parts manual but not really helpful
https://www.planetnautique.com/Corre...zr409parts.pdf

Maybe try contacting PCM and requesting a copy of the engine service manual?

[thomas205]

Since the new plugs no rough idling, fast idling or bad starts. Still don't feel I have fully diagnosed the issue as I think the boat running rich caused the plugs to foul and then the idling issue. I am going to look at testing the ECT sensor next.

[Boats Bros]

Did the new plugs solve your problem? Did you find any source of running rich?

[srock]

I have had the same issue and the same solution. When you do a little search it appears this boat is sensitive to old plugs as well as "equal" substitutions. Why, I have not idea. Also, watch the plug wires.