Large Frame alternator in M25XP

[Hayden Watson]

Has anyone installed a large frame alternator on a Universal M25XP. I am thinking about buying one and using a Zeus regulator to limit the output while pushing the boat but having up to 250A output available when charging at anchor.
I just want to make sure it will fit before I buy the alternator. In looking at the Balmar specs, it looks like there is very little difference in the actual case dimensions but about 1.5" difference in the mounting bolt center-to-center dimension.

 

[Stu Jackson]

Hayden, if you know the dimensions couldn't you figure it out? I believe the issue would be the clearance above the oil filter; assuming you have space above and to port.

 

[Hayden Watson]

Hayden, if you know the dimensions couldn't you figure it out? I believe the issue would be the clearance above the oil filter; assuming you have space above and to port.

If I was at home I could do that but I am currently in Tucson and have been talking to Tucson Alternator Exchange about building me a 250A external reguated alternator. The oil filter is probably the biggest thing I will need to avoid.
I guess that is another reason to go with a remote oil filter.
Speaking of which, do you know of a part number for a remote oil filter that will fit the M25XP?

 

[jssailem]

With tongue thrust firmly in cheek, are you confident the engine can turn that monster while you are motoring up current through passage?

It would be a bad day for an alternator and prop to stop that little engine.

 

[Hayden Watson]

With tongue thrust firmly in cheek, are you confident the engine can turn that monster while you are motoring up current through passage?

It would be a bad day for an alternator and prop to stop that little engine.

Absolutely confident my little 23-hp will be up to it.

• According to Balmar, a 250A alternator has a PTO load of 6.0-HP which will leave 17-HP for propulsion.
• Many C30's have been running around for decades with the Universal 5411 which is produces 11-HP.
• One of the most popular replacement engines for the C30 is the Beta 20 at 20-HP.
• I very seldom motor at over 1900 rpm which is near the peak of the torque curve and uses far less power at the prop.

Of course, none of that matters at all because with the system I am building I could still use this alternator if I had the 5411 with only 11-HP.
The secrete to this is the Zeus regulator. It can be set up to limit the power generated to any amount to meet the ability of the engine. At idle, it will produce 5A, then ramp up to whatever you set it to as the RPM's increase. I will set a 190A limit on the output because 200A is the max that my battery can take. The size is so that I can produce close to 200A for hours on end. I can also set it so that if I need to run at WOT, it will reduce the power so that plenty is available to the prop.

 

[shemandr]

In the current issue of SAIL Nigel Calder has a rather detailed article regarding charging of a LiFePo4 battery bank with alternator(s). I'm not going to try to summarize it (And I think there is a page missing in my issue) but it was worth reading.

 

[Hayden Watson]

In the current issue of SAIL Nigel Calder has a rather detailed article regarding charging of a LiFePo4 battery bank with alternator(s). I'm not going to try to summarize it (And I think there is a page missing in my issue) but it was worth reading.

Not having a subscription to Sail, what does Nigel charge to? I charge rather conservatively with bulk at 13.8v with 30-minutes of absorption. I float at 13.4v unless I will not be using the boat for a while and then I lower it to 13.2v.

 

[shemandr]

It would be wrong for me to misquote Nigel and I’ve sent that issue to recycling.
To do my best at a summary, I would say there is a section regarding heat management. There is also a section regarding the postitives and negatives of quick charging and a more sustained longer charge. I’m sorry but I can’t be more specific than that. He gets into different ways an alternator can be wound and the limitations of each way. There is a section, and maybe the point of the article, that compares 12 v vs. 24 and 48 volts systems in regard to charging.
He is specific about details of several alternator charging systems and if I were changing my set up I would take his opinions seriously.

 

[Stu Jackson]

Speaking of which, do you know of a part number for a remote oil filter that will fit the M25XP?

I thought you were already familiar with our C34 tech wiki

Replacement Filters, Belts, and Lubricants - c34.org

c34.org

 

[Hayden Watson]

I thought you were already familiar with our C34 tech wiki

Replacement Filters, Belts, and Lubricants - c34.org

c34.org

Thanks for reposting this. It is very helpful for bits and bobs for our engine, but I could not find anything on a remote oil filter. I did search the site for remote filter and found sever people who had not found a solution but no one who had a good solution. The oil filters flange on the M25XP is about 2.625" and the remote kits I have found have a 2.75"OD for the O-ring. I had one of these installed and one of the very few times I have ever gone at WOT, the O-ring blew out and drained the oil from the engine into the bilge.

 

[Hayden Watson]

Well, I pulled the trigger yesterday and ordered my 250A large frame alternator and serpentine belt kit. Let the fun begin.

 

[jssailem]

Just want to say...
You can not use that alternator during the Round Whidbey Race.

 

[Hayden Watson]

Just want to say...
You can not use that alternator during the Round Whidbey Race.

Don't need to because I can go 3-4 days without charging with 506Ah of battery. And I will not be running my computers too many hours each day. When they are running that is a bigger load than my fridge and freezer combined. Also we will not need the Starlink.

 

[jssailem]

we will not need the Starlink.

If one is racing, Starlink might be an edge. Weather updates occur about every 6-12 hours. Grib files for a program like LuckGrib may give you the most current wind racing data.

 

[Hayden Watson]

If one is racing, Starlink might be an edge. Weather updates occur about every 6-12 hours. Grib files for a program like LuckGrib may give you the most current wind racing data.

The problem with that idea is that it would leave Sue without internet and that would not be a good idea.

 

[jssailem]

A boat is filled with sacrifice and compromise.

 

[Hayden Watson]

Just want to say...
You can not use that alternator during the Round Whidbey Race.

You can and I have run the engine during the race. You just cannot put it into gear with the engine running. In the case of my AutoProp, it slows me down a huge amount if I let it spin so when I need to charge on the long-distance races, I tie the prop flange with a piece of string which prevents it from turning and keeps it feathered.

 

[Hayden Watson]

A boat is filled with sacrifice and compromise.

I make no sacrifice when it comes to the boat and there is no compromise!

 

[Hayden Watson]

My driving motivation for going to a 250Ah alternator is that I like to cruise and when I cruise, if there is any wind at all, I will sail. Last year I did a 14-day solo cruise and had decent breezes so that I did not need to motor much. Papillon uses 100Ah per day and after 8 days, I was down 540Ah and nearing the battery shutdown voltage the morning of my crossing of the Strait of Juan d Fuca which was my planned highlight of the cruise. The breeze was forecast to be +18 knots at an apparent wind angle of 120º P. A fantastic day of sailing. BUT...

I needed to replenish the battery and the next two days I needed to work from the boat at anchor so would be running the invertor to keep my laptop running for 16-hours each day which uses a lot of power. I did not relish the idea of running my engine at anchor and did not have my generator with me. That left me with one choice. I ran the motor in neutral as I sailed across the straight so that I could recharge my battery. from empty, it takes about 10-hours of run time to fully recharge. Now with the new system, I can fully recharge in less than 3-hours.

It will be limited to a max output of 190A but the higher output and large frame design will help it to run cooler with that output than the highest output small frame model.

 

[jssailem]

Great rationale!