How to look after a "new" diesel

[skipjack27]

Some on this forum will recall providing me with useful and interesting advice in relation to overheating, oil breather discharges, etc, for my Volvo Penta 200HP AQAD41A diesel (DP290 leg). The prevailing view was that in the long run there were no satisfactory "fixes" for these problems, and that this was a very tired engine deeply in need of a rebuild. Bowing to the wisdom of the forum, I sold my children, put my wife on the street, and stumped up US$21k for a rebuild.

As the owner of a bright, shiny, rebuilt D41A, I'm anxious to start out right and give this engine the attention it needs to stay in tiptop condition. In that interest, I'd love to hear what people have to say about the most important things to do to keep a "new" D41A happy and healthy. In particular:

- routine maintenance, especially running the engine in the pen during the winter months (it's winter here in Perth, Western Australia, at the moment). How often? How long? What revs? And why?

- use of cruising vs max rpm on the water. I've heard different estimates of how long a diesel should be run at max revs when out cruising to keep her healthy (10mins? 30mins?)

- what else should I be thinking about, or doing?

Any replies much appreciated.

Jeff

 

[kahuna123]

Re: How to look after a "new" diesel

I've run diesels for 20 year and never had a major failure. I tell you the basics I was taught by a 40 year veteran diesel mechanic. I am old school so I am sure things have changed. Keep in mind I am talking about my Perkins and Yanmars that turn around 3000.
1. The right props you should be within 200 -300 rpms of WOT out of gear. In other words where the governor stops you. How many time did we have a guy come in the marina and complain that he couldn't make rpms like he did from the factory. Only to find out that the wife had added 2000 pounds of decorations.
2. Cruise should be at least 200-300 under that. I have always had a feel of where the motor was running without undue strain.
3. I always "blew" mine out on the way home for just a few minutes. Maybe just one minute.
4. I changed the oil every 3 months regardless of hours.
5. Change the filters before you need to. Nothing worse than being in a rough sea trying to prime an engine. And that is when it happens.
6. If I had it to do over again I would install twin filters with a crossover valve. One gets clogged just switch over and change the dirty one at the dock.
7. NEVER let it get hot. Make sure your alarms work and are loud enough to be heard anywhere on the boat. I am assuming you have an autopilot and "sneek" away form the helm once in a while in an open sea.
8. I always closed the sea cocks. Opened the strainers and put the hose in there and flushed my motors out at the dock. But that was just me.
9. I would run it at least every other weak just to keep oil in the uppers and the fuel moving.

 

[skipjack27]

Re: How to look after a "new" diesel

Thanks very much, Kahuna123. Exactly the sort of wise and experienced advice I had hoped to get.

If you don't mind, I'll take some time to digest this - and perhaps get back later with some further questions that your interesting answer raises. Hopefully, this won't stretch your patience!

Jeff

 

[wi4x4man]

Re: How to look after a "new" diesel

One other thing about diesels, is that you need to make sure you work them! A diesel engine is not happy unless it is working. If you do a lot of put puttting around, you are going to start getting blow by or wet stacking, and if you continue on that route you will start to glaze the cylinder walls at which point your engine is toasted.

I recently dealt with a pair of 330 Hp 8.1L Deere engines in a 120' party boat. They put this massive boat on this tiny lake. Long story short, is that they never worked the engines because they never had enough room. If they opened her up, they would cause a wake (in a no wake zone go figure). One year later the engines were shot due to not being run hard enough.

 

[skipjack27]

Re: How to look after a "new" diesel

Thanks, wi4x4man. Fortunately, there is a fair bit of opportunity where I live to "work" the engine.

I'm still a bit unclear, though, as to just how much to work the engine. My D41A is rated, as new, as having a max rpm of 3700-3900. But it's rebuilt, not new. And I notice a 100rpm difference in the rev counters in the bridge and saloon control stations. So, I conservatively assume 3700 rpm to be the safe working max (WOT gave 4000 rpm on the sea-trial, by the way). My rebuild mechanic suggests no more than 3400rpm for normal cruising (an hour or so is a common cruising duration in my area).

So, I guess if I'm cruising around at 3400 rpm, how long should I flog her along at 3700 rpm each time I go out? (and is it advisable to push her up to the 4000 rpm limit? Presumably not as a routine thing -even for short periods).

Jeff

 

[Don S]

Re: How to look after a "new" diesel

You need to get the rpm verified so you know what the rpm actually are.

So, I guess if I'm cruising around at 3400 rpm, how long should I flog her along at 3700 rpm each time I go out? (and is it advisable to push her up to the 4000 rpm limit?

There is no need to run at 3700 rpm, many get there when getting on plane, but come down to cruise rpm after that. No real need to run at 3700 rpm.

3700-3900 rpm is max WOT under load you should get. Normal load, best trim, clean boat bottom. You should not be able to get to 4000 rpm, so how could you run at that rpm? If you can get to 4000 rpm under load, then that is your present WOT rpm, and you are under propped and need to increase prop size.

There is what Volvo calls "High idle" rpm, which is WOT in neutral. That rpm should be between 4200 and 4300 rpm, or your injection pump is not adjusted properly.
The biggest killer of the 41 series engines is bad injectors. The should be pop tested every few years to make sure they have a proper spray patter and proper pressure. When they start squirting straight fuel into the cylinders, that's when the oil gets washed off the cylinder walls and the rings go away fast.

 

[wi4x4man]

Re: How to look after a "new" diesel

What Don says is spot on with a diesel engine. Always keep it under the max RPM by a few hundred RPM. If you max it out at 3700, run her at 3400 to 3500. Get up on plane, and then back off several hundred RPM. Your engine will stay loaded, and you won't have problems. Your fuel consumption will also go down when you do that.

 

[skipjack27]

Re: How to look after a "new" diesel

Thanks, guys.

I'm especially grateful to Don S. He has identified exactly what my rebuild mechanic said on the sea-trial: the boat seems to be underpropped, and he suggested moving up a size or two. The mechanic remarked that the turbocharger was barely kicking in. I guess I tended to dismiss his assessment precisely because the boat on that trial had a a squeaky clean bottom, only 3 adults on board, and an empty water tank. I thought that loading up with water, people, growth on the hull, etc, would bring things more into normal running and justify the current prop.

I'm running on A3 Volvo DP290 dual props at the moment. Perhaps A4?

But on the more general question I was pursuing: is it, or is it not, important to push a diesel to its limit on regular occasions? Some mechanics have told me that it is critical to really run a diesel flat out for periods of time, and have talked about moisture in the engine, bedding down the rings, etc.

Anyone have any comment on this? Is it ok just to run at cruising revs (around 3400, in my case) - or should there be short periods of running flat out?

 

[Luhrs28]

Re: How to look after a "new" diesel

In my opinion just cruising (and having to accelerate from 0 to cruising) is loading the engines enough. I don't see anything to be gained by pushing the RPM up above 3400.

 

[Don S]

Re: How to look after a "new" diesel

You need to do your WOT tests and prop adjustments when the boat is at normal load. Not empty.

If you have a WOT rpm of 3700 rpm, and you normally run it at 3300 to 3500 rpm when cruising, there is no need to run at WOT. If you only run the boat at trolling speeds, then it would be a good idea to run at WOT for a while just to burn the fuel and moisture out of the oil. You will get just as much good from running at cruise speed as going to full speed.