Turbo Diesel Volvo Penta

[Man-O-War]

Hey guys, whats the word on 4cyl turbo diesel inboard Volvo Penta engines from early 90s? Model TAMD31B with counter-rotating propellers. Anyone with experience? Thanks in advance.

[bug_power]

Hey guys, whats the word on 4cyl turbo diesel inboard Volvo Penta engines from early 90s? Model TAMD31B with counter-rotating propellers. Anyone with experience? Thanks in advance.

...convert them to run on Veggie Oil and get more bang for your buck! I've got 3 diesels that we run on biodiesel and we're going to make one run on Vegitable oil. It's what Mr. Diesel invented the motor for!

[Steve-o]

Until recently I had an AD41A that I operated for about the last thousand hours of its life, and it was a good engine. The 31 as I understand it is a smaller sibling built on the same technology. B series engines had slightly raised compression to address a cold start smoking problem that many operators in nice harbors did not care for. I live in a temperate climate and do not find the A model to smoke excessively. In cold weather, the 17.5 compression vs 16.5:1 compression makes starting a little easier, but that's probably below 40 degrees F. Are there any specific questions you have? They can be good engines if well-cared for, and the 290 duoprop outdrive is about as good as they come. I'd highly recommend joining boatdiesel.com for $25 to access all forum archives, for marine diesel discussion on the net, that is the place to be.

[Man-O-War]

Thanks guys. All the documentation I could fint was for the 31A model, and it now makes sense because boat/engine are in NorthEast and higher compression from 31B is more needed. I was just looking for any inherent problems that this particular engine might have/had, wanted to make sure it was a good platform. I'll join boatdiesel and look around there.

[Steve-o]

The 41 intake manifold features a number of removable plugs, which can be used to tap for boost gages or putting glow plugs in, which also make cold starting easier. As far as I can tell the A series is more common, but the engines are pretty similar, and I don't know if B engines were routinely fitted with glow plugs or not, perhaps they don't really need them.

The biggest problem would be regular maintenance and overloading. The 41 should spin up to 37-3900 RPM with a loaded boat. I am continually stunned by the number of folks who don't get this, as though it were not critical to engine life. The 41 series could also be had in ratings intended for commercial use (41M, etc I think). These were rated at lower RPM and lower HP, for closer to continuous output, but they were not the A, B or P models, which were all for pleasure use. Beware any owner who messed with the injection pump to try for more power, or who does not think the engine has to hit rated RPM, or doesn't know what that means. My 41A had 3000 hours on the clock and was still running strong when it was killed by a catastrophic part failure, which seems to have been a fluke occurrence. You can get a quick and dirty idea of cylinder wear by inspecting the crankcase breather canister on the back near the air filter and aftercooler, it looks like an upside down coffee can. It unscrews about 3/4 turn to come off, and you can see how much oil is in it. The less the better, but don't be dismayed to see some because it is bound to happen. On newer engines it is popular to install aftermarket crankcase breathers in order to reduce the very fine oil mist that will eventually be deposited inside your engien room, and if something like this is fitted instead of the stock part, I wouldn't be worried, and it might even be a good sign, since the owner knows a little more than the average bear.

Boatdiesel is a great resource, expecially if you are boat shopping. The spec sheets for many manufacturers are available going back for years, and there are some very knowledgeable people on the forums. Good luck.

[Man-O-War]

Thanks santiago!!!!

Its not as clean as yours, but it supposedly works great. No modifications on it. New hoses up top. I'll go check it out.

[Steve-o]

My pleasure. I really should be studying though. A little rust is not the end of the world, but I'd check for rusted bolt heads that might give you trouble down the road. I'll add a few more things that came to mind really quickly.

You can easily pull the intake manifold plug closest to the aftercooler, and check with a small light to see if you can spot any white salt crust, which would indicate an aftercooler leak. The aftercooler should still be cleaned and checked even if it doesn't leak (unless you have records of when it was done last), but the owner might not want to pull the core out for you. If you're not familiar with turbodiesels, the aftercooler is that finned box on the right in your photo, and it ducts cooled turbo air into the intake manifold right behind that orange cap on top of your injection pump. The air coming from the turbo is pretty hot, and the aftercooler pumps seawater through tubes in the intake air stream to cool it down. If one of these tubes begins leaking, you'll be feeding the engine a steady diet of seawater mist, with is not something it needs.

Seeing a fuel filter like the Racor in the foreground is always good. There is a filter on the engine, but that is a "last chance" sort of filter and should not be used as the primary. You could also check out the air filter inside that black plastic drum on the turbo, just to see how dirty it is. The oil mist I mentioned before just happens to come out right next to the filter, so they pick it up and take on a black dirty appearance before too long. Hopefully it is not filthy. That crankcase breather is the round perforated can-like part I was trying to show in my photo. I bet it is in the same place on the 31.

Open the coolant fill cap and see what color is in there. VP uses aluminum and iron together in some engines (the 41-43 series at least, and I am pretty sure the 31 also), which requires some special coolant to prevent problems. VP coolant is green, and despite being expensive is all I have been willing to use, just to be safe. Yanmar uses similar construction, and I know an excellent Yanmar and Cummins installer who has good luck using Fleetgard (I think) in Yanmar since it meets the specs, but I wasn't willing to experiment on my engine. I guess what's good for Yanmar iron and aluminum engines is good for Volvo ones too, but if Volvo used a different alloy back then than what they use these days, maybe the VP coolant is worthwhile. But using just any old automotive coolant is asking for trouble.

You can always send an oil sample for analysis, but you'll need to know how long the oil has been in the engine, and it would help to know the brand and weight. This costs about $30 at a company called Blackstone, which is widely regarded as one of the best, and the people there are pretty nice. If you need help understanding what the results mean, they will go over them with you. This can give you a ballpark range of how the engine is doing for the number of hours it has.

I forgot to mention that you'll need a photo tach (the one's I've seen have been hand held devices) in order to get an accurate read on engine speed. The factory engine tachometer is not accurate enough for this. There are aftermarket tachs that use a magnetic pickup to count the flywheel teeth, but I don't know anyone who has gone to the trouble of drilling and tapping the bell housing on one of these engines to put one in, although it is a fairly common method on newer marine diesels. If this engine happens to have one, that might be accurate enough, but using alternator output for the tach signal is too unreliable for precise measuring.

[Man-O-War]

Thank you SANTIAGO!!!! Now go back to studying! :)

I picked up the boat/engine, will get it all checked out as per your suggestions

[CWitch]

My 41 series was a complete nightmare. Corrosion and expensive parts would stop me from another purchase. Check the price on a few parts...you will see what I mean.

[Steve-o]

Can you elaborate on the corrosion problem?

Yanmar parts are even worse, but that's probably the way I'm headed.

[CWitch]

The 40/41 series uses numerous types of hi-tech metals. Mix them around and you have a uphill battle fighting electrolysis. The intercooler, turbo and oil pan all disintegrated after time.

I agree 100% on the Yanmar. Their heat exchangers and turbos are notorious for corrosion and electrolysis. There are not enough zincs on the motors. I understand the excitment surrounding Yanmars when you look at HP vs weight but they are simply not not high hour big iron diesels and you will put all the money you saved in gas back in the power package keeping up with the repairs and maintenance.

I have owned Cats, Cummins and Detroits with almost no corrosion related problems. The Cummins B-Series 5.9 is a durable and relatively light package with respectable HP to weight numbers. Good luck with your diesel experience.

[StabbinBoy]

My first boat had those motors - what a friggin nightmare.
The parts were soooo damn expensive that i bought a used Volvo engine for salvage parts until i could finally sell that lemon.

[Steve-o]

The 40/41 series uses numerous types of hi-tech metals. Mix them around and you have a uphill battle fighting electrolysis. The intercooler, turbo and oil pan all disintegrated after time.

I agree 100% on the Yanmar. Their heat exchangers and turbos are notorious for corrosion and electrolysis. There are not enough zincs on the motors. I understand the excitment surrounding Yanmars when you look at HP vs weight but they are simply not not high hour big iron diesels and you will put all the money you saved in gas back in the power package keeping up with the repairs and maintenance.

I have owned Cats, Cummins and Detroits with almost no corrosion related problems. The Cummins B-Series 5.9 is a durable and relatively light package with respectable HP to weight numbers. Good luck with your diesel experience.

I was lucky enough to avoid those problems for 3000 hours, but I used the Volvo coolant like it was religion. I agree completely on having enough iron for the HP. My boat is not a race car, and lightweight, high output, high speed diesels worry me. The 6B is a wonderful engine in my opinion, good output and service life and reasonable to rebuild. I'd like to have that over anything else in the size range.