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Technical: Alternator Upgrade on Volvo Penta D2-60

WARNING, this is a TECHNICAL post.  Those only interested in human interest stories should skip it!  It would have been helpful if I had the information I am sharing before I started this project.  So, for those interested in upgrading an alternator on a boat or just like technical boat stuff, read on.

The Why

When living on a boat full time, getting the right balance between power consumption and generation is critical. As part of our effort to keep Gerty simple and minimize the number of systems we need to maintain, we decided to focus on two charge sources, solar and the engine’s alternator. Our plan is to optimize the sources to be as efficient, robust, and fault tolerant as possible, and then maintain them well.  This means no antennae or wind generators shading our solar panels.  It also means that the 115 amp internally regulated alternator that came with the engine needed to be upgraded.  The base alternator produced about 80 amps maximum, which was enough to run our water maker or charge our batteries, but not both at the same time.  In fact, it could not charge our 660 amp hours of AGM batteries at their maximum absorption rate.  We plan for our next set of batteries to be lithium based which will have an even higher absorption rate.

Our decision to upgrade the alternator can be distilled to two reasons.  One, we wanted on demand generation without adding a diesel generator.  Two, we wanted to minimize how long we had to run the engine when we need to charge.

The Planning

I did a lot of research, and there was a dearth of information on upgrading a Volvo Penta D2 series diesel with a high output alternator.  The little specific information I found on Penta D2 alternator upgrades uncovered scary stories about people that had messed with their Volvo alternators.  Apparently, the engine electronic system would return alarms – a.k.a. rejecting the transplant specimen.  In effect, these people were being berated by their engines post op.  

Another challenge was that the Volvo engine came with a five grooved serpentine drive belt that, while better than a typical v-grooved belt, was not wide enough to handle the horsepower of a very large output alternator. 

I started considering other options. It turns out Volvo makes a second alternator bracket and kit. You can mount an additional, identical alternator in a separate location to increase capacity. At first this seemed like a reasonable alternative.  Until I found out that Volvo wanted about $1,400 just for the bracket and related pulley.  Add in the cost of a good alternator and remote regulator and this option became very expensive for something I did not consider ideal.  So, I dug deeper into replacing the original alternator.

I only found two companies that alluded that they could get their high output alternator to work on our Volvo Penta D2-60.  One was Electromaax, the other was Mark Grasser DC Power Solutions. Electromaax was less expensive and full of promises, but the more I dealt with them, the less confidence I had. Eventually, it became clear they could not delivery a good solution.  

I found out about Mark Grasser DC Power Solutions through Bruce Schwab at Ocean Planet Energy.  Bruce was helpful in building my confidence that Mark Grasser alternators would work on the Volvo.  Once I had the product in hand, Mark Grasser was friggin awesome!  I give him an A+ for customer service.  Mark ended up producing custom pulleys for the crankshaft and water pump that accommodate a wider eight-grooved serpentine belt, as well as a 250 amp remote rectified alternator.

Mark’s kit before anodizing the pulleys red and making other ‘tweaks’

Mark’s setup is expensive, but it has several advantages.  For one, the custom pulleys change the pulley ratios.  The old alternator did not start producing significant power until we got the engine up to 1600 rpm and it needed to be above 2000 rpm to produce at full capacity. With Mark’s larger diameter crank shaft, water pump pulleys, and smaller diameter alternator pulley, the alternator can produce much more power at a much lower rpm.  This is possible because Mark’s alternator can handle the resulting peak RPM when the engine is at full throttle.  Even at idle it can put out a lot of power.

Another advantage to the setup Mark provided is that he removed the rectifier from the alternator.  Rectifiers generate a lot of heat.  In separating the rectifier from the alternator, Mark can supply a huge rectifier rated for 400 amps and mount it on aluminum cooling fins with a 100,000 hour cooling fan.  This can be mounted outside of the hot engine compartment.  All this allows the alternator to run continuously at peak load without overheating and without shortening the alternators life – a promise many manufactures make but few deliver on.  There are many advantages to this set up.  For one, alternators produces more power the cooler they are.

I decided to complete the setup with a the Balmar MC-614 regulator.  This regulator is well regarded, can handle our future lithium battery dreams, and has the capacity to ‘throttle back’ the alternator output.  Based on my research, reducing the alternators output to 85% of its full capacity can significantly increase the life of the alternator.  With a huge 250 amp alternator, losing 15% peak output in order to gain a much longer life is a trade off that works for us.

The Installation

The installation process went pretty well. There were only seven challenges (pc for ‘problems’) and it took twice as long as expected.  Not bad for a boat project! 

I did the installation over our off season (New York winter) when I had plenty of time to get everything resolved elegantly.  This was wise.

Challenge #1 – When I took off the old alternator and went to fit the new alternator.  It turns out that the alternator mounting bracket needed to be modified since the new alternator was being moved forward a bit to accommodate the new pulleys. I had to shim the engine up to remove the main engine support bracket. Mark agreed to modify the bracket for me.  I shipped it to him, and it came back perfectly machined.

Challenge #2 – The holes on the main crank pulley, related bolts and the holes in the alternator bracket were too small.  I shipped these to Mark as well for enlarging and new bolts. 

Challenge #3  – The rectifier did not have a D+ connection.  In my research, the old alternator had a sensing connection from the engine to the alternator’s D +. I concluded that this connection was critical to avoid the alarm problems that other people had had. Mark agreed to build a D+ connection for the rectifier and ship it to me.

Challenge #4 – I could not get the pulley off of the alternator.  It was too tight.  This was necessary to put a washer behind it to move it forward a little. Once again, a call to Mark solved the problem.  He said, “take it to an auto mechanic – they can get it off for you”. Sure enough, it took the auto-mechanic 10 seconds with their hydraulic wrench to get the pulley off. 

Challenge #5 – The outlet cable in the back of the alternator was conflicting with the side panel.  Again, Mark came through and rerouted the cable exit for me.

Challenge #6 – There was no obvious way to get 12V power to turn on the regulator when the engine “on” button was pushed. Volvo is using electronic controls for the “on” and “off” buttons.  Mark custom built, using a series of relays, a switch that turns on when the start button is pushed and stays on until the stop button is pushed.

Mark’s solution works but is a bit complicated.  I would love to hear from anyone if they know a better way to control a 12V switch from the Volvo D2 “on/off” button.

Challenge #7 – The alternator adjustment arm also had to be moved forward.  This was actually a known problem before the installation started.  Once again, Mark did the modification of the arm and shipped it back to me.  

Obviously, Mark’s follow up service was great!  He sells a premium product and then works to make sure the installation goes well. This was a pleasant surprise compared to many other marine vendors I have dealt with.  The good news for anyone else who wants to do a similar upgrade is that now Mark understands the nuances.  I suspect his next Volvo D2-60 kit will require few tweaks.

Note that the installation also required upgrading the cables from the rectifier to the battery bank to a heavier gauge, removing our old Sterling alternator to battery charger (which we sold), and rewiring the engine compartment exhaust fan.

The Results

Now that we are living on the boat full time, we really value this upgrade. So far, the new alternator has been working flawlessly.  Even suppressed to 85% output we have seen it put out about 200 amps.  No matter if we are at low engine RPMs, or are making water, or are running the microwave, or all of the above, the alternator is putting significant amps into our batteries.  We are confident it will have a very long life since it is kept relatively cool and is a modular setup.  And, the red pulleys make the engine look snazzy.

We are now finding that our AGM batteries are the weak link in our power setup.  They cannot take the new alternators peak output.  We are only getting full utilization of the alternator when making water and charging simultaneously.  Even then, the AGMs do not allow for high absorption rates for very long.  We are one step closer to the perfectly balanced system, but until we upgrade to lithium based batteries we won’t see the full benefit of our new alternator.

This Post Has 14 Comments

  1. Excellent article Michael! This information is super useful. That’s pretty good service that Mark was able to do both the metal work, the changes to the rectifier, and the relay box. Would have been a pain otherwise.

    Do you know what the D+ sensing line is actually needing to sense? My guess is that the ECU is checking the voltage out of the alternator? I wonder if someone could just wire it to the output wire of the alternator to bypass this?

    Regarding that relay box. The texture makes it looks like it was 3d printed. I’ve not worked with a Volvo before. Other marine engines I’ve seen usually have a oil pressure sensor wire to the control panel that can be used to indicate if the engine is running or not. If, on the Volvo, there is such a thing, you could in theory rig a single relay off that. However, I’m suspecting that couldn’t be done here.

    BTW, love the red pulleys. But why bother anodizing them?

    Looking forward to seeing an article on the upgraded batteries! I’m curious on how much space the 45.9 has available for batteries.

    1. I believe you are correct that the engine is sensing the alternator voltage. The output from the alternator to the remote rectifier is three phase AC so I could not connect the sensing wire to that. Connecting the sensing wire to the rectifier output would show voltage from the batteries even when the alternator was not working. Perhaps this would solve the false alarms – not sure – did not try it. However, it would also disable the alarm functionality. We concluded the best option was to replicate the D+. Mark fabricated a simple D+ with three diodes that is connected on the alternator side of the rectifier. Seems to work great.

      It is possible that the oil pressure sensor is 12v. I will look into that. Many of the other voltages are odd since much seems to be digital. We knew that the start and stop wires were 12v so that was how Mark solved it. I suspect there is a better solution. Note that Mark was a bit embarrassed by the 3d printed relay setup. He said it was sloppy and that he is going to get it printed on a circuit board. I will likely have that in July.

      Originally Mark had painted the pulley – but that was not ideal since paint does not hold well on aluminum. Mark agreed to anodize them for me. I did not pick the color but think they look great. The anodizing should help minimize any aluminum corrosion.

  2. Mike – I could say I read the whole thing and then make intelligent comments like Gary but then you would know right away that it really wasn’t me. So, let’s just say that I did read the whole thing. Be safe, Mark

  3. Hi Michael
    Great post. Will be looking foreward to the Lithium-batterie installation.
    Is the Volvo standard from the yard?
    Or is it possible to have a Yanmar instead? (Volvo spare part tend to be expensive.)
    And do you think there would there be the same challenges with opgrading with a Yanmar engine?

    PS: I drive a Volvo and have no issues with the Swedes 😉

    1. The Volvo is standard for Allures and Garcia. I do not know how the yard would react to a request for a Yanmar.
      I believe Mark Grasser has alternator kits for Yanmar engines. I do not know if these are more or less complicated than updating the Volvo.

  4. Michael
    Can you advise if the alternator upgrade voided the Volvo Penta warranty on your D2/60 engine?
    From your report and photos, it appears you have kept to just one alternator on the engine, albeit a large one. Is this correct? I am interested to understand how you /Mark Grasser plan to manage charging on the starter battery and the larger lithium bank you plan to install, from the single alternator.

    Good job!

    Anthony

    1. Anthony,
      -I am not sure if the alternator upgrade voided any aspect of our warranty. Our engine is over three years old so most of the warranty is expired. I was not too worried about it but on a brand new engine it might be a concern.
      -You are correct that we have one alternator.
      – I have now installed the lithium bank. The starter battery is charged via a Sterling battery to battery charger. This allows for a different charge profiles for the house and starter. Today I charged the lithium bank to 100% for the first time. The alternator ran full force for about three hour to get the bank to 100% (they shipped at about 10% charge). The alternator did not overheat or throttle back because of high temperature. I was impressed! And, the lithium batteries sucked up all the amps the entire time. The old AGMs batteries could only utilize the full amperage of the large alternator for about 15 minutes. This is a huge difference.

  5. Hi. I have a different engine, a Nanni 4.220 50 hp. My approach was to leave the engine alternator, electrics and starter battery totally as supplied and to hang another 100 Amp alternator below to charge the 300 Ah AGM house bank via a Balmar regulator. Designing and building the bracket was a challenge. I used a Bosch alternator and replacement brush holder for the field wire. Very cheap. Has worked for 20 years and 40000 miles. Will go Lithium soon. Could supply photo if interested.
    Great article. Thanks. Liked your comment about avoiding the shading of the PV array.
    Peter (Australia)

  6. Michael, thank you for this. This is precisely what we want. We will get Lithium from the start (GL should start building our 45.9 in July, but GL does not grant our request to install a higher output alternator (including all the upgrades needed for this) because it involves everything you describe above end they do not want to deal with it.
    It does puzzle me, that for a boat that is designed to go long distances they do not offer this.
    Or for that matter, the “low-output” solar panels that they offer and are not willing to install higher-output solar panels.
    When we ordered the boat (September 2020), 550W was fair, at the time of delivery (end March 2023) 550W is just ridiculously low.

    1. Last I heard Mark Grasser had a long waiting list for his builds. You may want to keep that in mind.

      We have 600w of solar. Of course more would be better! Most important things is to be vigilant about not shading your solar.

  7. I too had a dilemma regarding the charge rate of the stock Volvo alternator on a recently installed Volvo D2-55F. (predecessor of the D2-60). The alternator, if used to accommodate multiple outputs would cause alarm problems with that Volvo MDI (a monitoring computer that Volvo for some mysterious reason attached to it’s heat exchanger–heat!) After the MDI failed for the fourth time, (and after Volvo cut me loose for warranty) I simply replaced it with off-the-shelf Faria meters, a classic Perkins wiring harness and three relays… Voila! no more problems at a fraction of the cost of a replacement MDI…
    However I did get the Volvo mounting bracket to run a second 200 Amp (240 peak output) from Delco Remey 28SI. I did have to replace the 4″ pulley that Volvo sent with the bracket with a 6″ I had made at speed shop. The alternator I had fitted with a 2″ (3:1 ratio) at the alternator shop where I bought it. At idle (1000rpm ) the alternator (with a Bamar MC-618) puts out 160 amps into my “Firefly” batteries and I’ve seen more than 215 amps at cruising speed (as seen on a Balmar SG200 monitor). I do have an engine blower offering outside air to the back of the alternator (diodes). But the alternator has yet to get more than warm… Two alternators, two separate serpentine belts and a reasonable cost alternative.

    1. Sounds like another good option. When I researched the 2nd alternator mounting bracket from Volvo, they implied it was not structurally rated for loads from a 200amp alternator. I suspected it would be fine, and I am glad it is working well for you.

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