Re: Which oil [Daniel's engine-start/stop protocol]

David Vogel

Hi Daniel,

Several things here – and I am no diesel mechanic – although I do try to distil the best operating practices from those marine mechanics who seem to know a thing or two. And like you, not proscriptive, but offered to the group on the off-chance it may be of use to someone ...


My usual start-up practice, if the engine has been left sitting without start for longer than about, say, 10 days to 2 weeks, is to be in the engine room, manually move the fuel shut-off lever to deny fuel supply to the HP fuel pump (or divert fuel away from the injectors), and ask someone to crank the engine for a few seconds, maybe two or three times of 5-10 seconds each over a minute or two. I avoid continuous cranking 1. to avoid overheating the starter-motor (and cables/connections) or draw down the battery unnecessarily; and 2. as well as to reduce the potential to draw water backwards through the exhaust manifold into the cylinders. As soon as the cranking produces oil pressure, I stop. The main purpose of this exercise is to ensure that engine lube oil, that otherwise may have drained into the sump, is moving through the galleries and is available to various bearings, whilst maintaining combustion-related and rotational loads to a minimum. The engine oil is ‘cold’ (atmospheric ambient being cold, when compared to operating temperature), and this is why I use the specified multigrade 15W-40 oil (rather than a mono-grade oil), as the viscosity of the multigrade oil, even when at non-freezing ambient temperatures, will still be sufficiently fluid to be pushed at cranking speeds to where it needs to be. A single-weight oil (such as straight 40W) flows more easily only when raised to close to operating temperatures. Conversely, multigrade oils retain better lubricating properties at high temperatures, than mono-grade oils, all other things being equal. Once the oil alarm (light &/or aural alarm) stops alarming, I can then proceed to the actual start. I can normally feel and hear when enough oil has circulated through. Speaking from experience, if I do not do this pre-crank, then I find that the first few seconds of engine running have a different sound, with a bit more clunking and mechanical vibration, at least until the oil alarm stops. All other things being equal in a properly maintained engine, the majority of wear occurs within the first few seconds of operation. So I like to minimise that kind of avoidable wear and tear, if I can. BTW, if there is going to be a lot going on (e.g. new crew or passengers), I like to do the engine first-start and warm-up before the guests arrive on-board (voice of experience speaking here ;-). For an after-dark departure, I will set things up before sundown (more experience speaking).

Once the engine is started, all alarms silent, with things sounding normal, exhaust spitting away as it should, siphon gurgling, I then, whilst remaining in neutral, slowly advance the throttle to obtain 1,200RPM temporarily, and then retard to idle. I do this because, even though at slow idle there ‘should be’ enough pressure generated by the Hurth ZF-25 gearbox’s internal hydraulic pump to open the reverse back-flow preventer and circulate the hydraulic oil, I know from testing that my hydraulic pump is not in as good a condition as is was out of the factory, and I need to give the engine a gentle blip to raise the operating pressure in the gearbox, and this happens at about 1,000RPM (at which point the gearbox’s pressure starts to gently pulsate)*. Retarding the throttle to idle, the gearbox hydraulic circuit remains pressurised, so that when it comes time to engage gear, this happens smoothly and quietly, without any undue clunks or thuds.

I try not to apply any significant power (say, above 1,600RPM) until the engine is at least 50% of it’s normal operating temperature. As soon as practical after start, as part of my post-start checks, as soon as I have a temperature reading, I engage firstly forward, at idle, then back to neutral, and then select astern, still at idle, to listen and feel for the proper operation of the gearbox, and for any vibration from the prop. I then place the engine under load (in astern), increasing first to 1,000RPM, pause, then to 1,200 RPM, pause, and then to 1,500RPM. At some stage within about the first 90-seconds after applying power, I will hear the high-output alternator come on-line. I visually check the output current and voltage of the 24V alternator at the 24V panel. I leave the engine at 1,500RPM astern, as I believe that the engine will warm quicker under load, than at idle. (I have a Bruntons's Autoprop, which presents the same blade faces to the water, whether running astern or forward; and it is treated with PropSpeed, so this slow running also assists clean the prop of any material than can be removed by spinning up of the prop which, advisedly, should in any case be done every 2 weeks, when at rest.)

While the engine is warming, I complete any outstanding engine room checks, especially if the engine has not been run for some time, and I want to be sure that everything down there is as it should be. Before then doing the walk-through both below- and above- decks. Any final crew-briefing and last preparations complete, back to the helm, retard the throttle, select neutral, and then get underway.

It’s pretty much the same patter, whether we are moving the boat 50m from one berth to another or to the fuel pontoon, or departing for a 3,000nm trans-oceanic. This way, I have a feel for what everything sounds and feels like, and as well how things change with time. I was surprised how different things sound and feel with fresh oil and new filters even though, upon reflection, it all makes sense.

It is being sensitive to these ‘little things’ that has meant, on more than one occasion, an imminent failure has been caught at the earliest stages, with early intervention avoiding some very noisy (and expensive) damage to the mechanicals. (Thinking here, avoiding a gearbox failure, when the non-Bowman oil-cooler bled out.)

As for shut-down, with a turbo, my routine is a little different than for a vessel with a normally aspirated engine. In my case, when entering a bay for the final run-in to the anchorage, I slowly increase the revs to 3,200RPM (~85% WOT, or max continuous power), and let it settle for a few minutes, then open the throttle fully to WOT for ~30 seconds (I should see ~3,750 for my Yanmar 4JH3-HTE) – I note any temperature rise, as usually there is about plus ½-a-needles-width when running at sustained high power. Then return to 3,200RPM, holding it there for 3-5 minutes. This is to burn off any carbon residue from the turbo. I then gradually retard the throttle to appropriate manoeuvring revs (typically, say, 1,500 - 1,800RPM) until needing to coast to the selected anchor spot. I idle into position and, depending on the bottom topography and proximity of other vessels, normally drop the anchor whilst going astern at idle (with the mizzen 2/3 out, and centered), so as to lay the chain and assist a nice set of the anchor. To check the set of the anchor, I will gradually run up to a usual maximum of 2,000RPM astern, but will take it temporarily to 2,500 if the situation warrants. I retain idle astern to assist the forward deck crew with placing the snubber. Once that's done, I then select idle in neutral. l always allow 3-5 minutes cool-down after running at anything over 1,500RPM. I also do not do any of the rev-and-switchoff routine that I hear some others do. I am in no hurry to switch the engine off, doing so only when I am confident that we are secure, with no further need to move under power. Typically, no more than 5 minutes after the snubber is on, in which time the mizzen is stowed, helm tied-off, and sail-control-lines secured. I am not worried about carbon fouling of the turbo (or exhaust manifold) in those 5 minutes or so, as the engine cannot be over-fuelled (enough to produce carbon soot) while idling in neutral.

I hope this helps, and if anyone has a different process, or any comments, questions or suggestions, I am all ears.

Best to all.

SM#396, Perigee, Whagarei, NZ
(we're in Oz, presently in COVID-isolation)

* BTW, this looking at the gearbox hydraulic pressure, and when the hydraulic system first pressurises after a start, is a useful first-order diagnostic test for the health of the gearbox after an "event", such as an oil-cooler failure and potential gearbox over-temp. The theory goes like this -- advisedly, the gears of the Hurth ZF25 internal hydraulic pump are more susceptible to damage resulting from lack of lubrication and overheat, than are the main drive gears of the gearbox itself. If the hydraulic pump is still pressurising at low revs (idle, or at least <1,000RPM), then the gears of the hydraulic pump are unlikely to be damaged and, so too, the planetary drive gears of the gearbox are also likely to not be seriously damaged. This diagnostic being done in conjunction with a borescope inspection of the gearbox internals, and (of course) it is not absolutely definitive - such can only be done by removing the gearbox, and breaking it down for a complete detailed inspection (which introduces it's own issues, not the least being the availability of a rebuild kit, especially in remote areas - but that is another story). Nevertheless, such a pressure-test does provide some piece of mind about the state-of-health of the gearbox, when everything else looks, sounds, and feels normal, and other options are limited.

From: <> on behalf of Daniel Alexander Thompson <Thompson.Xander@...>
Reply to: <>
Date: Sunday, 10 July 2022 at 6:06 pm
To: <>
Subject: Re: [AmelYachtOwners] Which oil

I’m going to go with Shell "petroleum distilled oil" (mineral oil) . I have about 80 litres of synthetic to get through, first. I will do a double change, when I switch out. 
Colin. Do you ever use SAE40 or always 15W40? Reasoning? Do you have any pointers when buying the Shell petroleum distilled oil. Is it “pretty much a muchness” or is there some nuance to the specification of the oil? 
Slightly off topic, here:
My protocol vs. engine starting. (This is not advice.)
I try to never start the engine unless it has not been started for six weeks. In which case I will start it and run it for minimum one hour under full load motoring 1600 rpm. I believe that this thoroughly lubricates all the seals and bearings which will have dried out.
When I start the engine, I run it for thirty seconds at idle and then gradually increase rpm over the next thirty seconds. Then I apply load at the sixty second mark to move the boat and increase to 1600 rpm within a few minutes. So I start the engine very near the point at which I need it.

When shutting down the engine I only let the engine idle for about thirty seconds before shutting it down (I don’t have a turbo to run down).
I try to keep a load on the engine and almost never idle the engine unless this avoids stopping and starting. Basically attempting to maintain a good operating temperature so all the rings etc are at an optimal diameter.  
(I used to own a big Iveco truck and I couldn’t get my driver to stop “warming up” the engine at idle for half an hour. I believed he was destroying the engine)
I would very much appreciate Colin and David’s thoughts vs this protocol.

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