Alternator Temperature Sensors

[colemj]

The rpm control is the biggy for me. spinning 250A from a 35-year old 23-hp engine takes some control.

Yes, that was one of the reasons I gave for needing a Zeus/Wakespeed over a Balmar.

BTW, it is almost universally considered bad to connect a large alternator to a small engine, but I agree with you that this is the best thing one can do if adding an alternator.

Mark

 

[Hayden Watson]

Yes, that was one of the reasons I gave for needing a Zeus/Wakespeed over a Balmar.

BTW, it is almost universally considered bad to connect a large alternator to a small engine, but I agree with you that this is the best thing one can do if adding an alternator.

Mark

I am glad that you qualified that with "almost". Nigel Calder is one of those in the "almost" category of being a proponent of mounting a big alternator on a small engine as long as it uses proper regulation.

Earlier you said, "In our case, we have a 3.5kW alternator on a 55hp engine." That would be 291A at 12v which most would consider to be a pretty big alternator on a small engine.

A prop has a non-linear proportional power demand in that as the rpm increases, the rate of increase in the load gets greater at a much higher rate than just a linier 1:1 ratio. The rpm/load graph makes an upward curve.

An alternator has a non-linear inversely proportional power demand in that as the rpm increases, the rate of increase in the load gets smaller at a much higher rate than just a linier 1:1 ratio. The rpm/load graph makes a downward curve.

On our diesel engines, the rpm/torque and rpm/hp power curve is non-linear inversely proportional. This means that for the alternator, the power curve the engine easily supplies the demand of the alternator. For the prop, on the other hand, as the prop is getting to its greatest demand, the engine is losing the ability to cope with that demand. Because of this, the peak prop load which occurs at max rpm and all other speeds, there is a lot of unused power that can be used for other purposes.

 

[Hayden Watson]

They did. I sent in a support request online over the last weekend, on Monday afternoon I got a response.






The shaft diameter is the same, however the J6 pulley has a small protrusion on the back of the pulley that allows it to be screwed down tight. The J10 lacks this protrusion and cannot be tightened down. I was dealing with The Yacht Rigger in St Petersburg FL and they were going to let ARCO know, I also sent in a comment to them about the same issue.

Since Arco is in Pensacola, you might stop by and inquire, maybe if they get enough disgruntled Balmar Altmount customers complaining they'll figure out a solution.

I got several different thicknesses of alternator pulley shims at my local auto parts store and was able to get a perfect alignment of the J10 pulley.

 

[dlochner]

I got several different thicknesses of alternator pulley shims at my local auto parts store and was able to get a perfect alignment of the J10 pulley.

Thank you. I didn't know such a thing as alternator shims existed.

Earlier this week I finally got the alternator working again, after suggestionss by @Maine Sail and @Ralph Johnstone to use a large hose clamp, a quick response from BoltDepot.Com to replace the #12-24 nut that decided to hide in the bilge, and remembering to turn the alternator service disconnect switch back on.

Thanks for all the suggestions and insights.

 

[colemj]

Earlier you said, "In our case, we have a 3.5kW alternator on a 55hp engine." That would be 291A at 12v which most would consider to be a pretty big alternator on a small engine.

275A. I was calculating at 13.4V, since that is the voltage the alternator is at for 90% of the time during battery charging. While that is technically 3.685kW, I rounded to 3.5kW. Besides, it settles into ~230A when heated up, so I'm only seeing a bit over 3kW in practice.

Our boat was designed for two 40hp engines. This is more than enough to operate the boat in all conditions. The person who commissioned our boat had them put in two 55hp engines. These are totally unnecessary, so have at least 15hp each to spare.

Mark

 

[Hayden Watson]

275A. I was calculating at 13.4V, since that is the voltage the alternator is at for 90% of the time during battery charging. While that is technically 3.685kW, I rounded to 3.5kW. Besides, it settles into ~230A when heated up, so I'm only seeing a bit over 3kW in practice.

Our boat was designed for two 40hp engines. This is more than enough to operate the boat in all conditions. The person who commissioned our boat had them put in two 55hp engines. These are totally unnecessary, so have at least 15hp each to spare.

Mark

It would not have mattered if you had the original 40hp engines and they were running at 100% of their max power when at wide open throttle (WOT). The prop can only take that full power with it is spinning at max rpms. Anything less than that and the prop will require much lower power from the engine. On my Universal M25XP if I was perfectly propped so that it used 100% of the 23-hp at WOT of say 3,200-rpm, if I drop the rpms to 2/3WOT or 2,133-rpm, the prop only needs less than 40% of the hp or 9.2-hp. I motor 95% of the time at 1,900-rpm and the prop needs less than 9-hp at that speed. Here is the M25XP power curves with the approximate prop demand shown in red and the alternator demand curve in green.

As long as the total of the red and green curve added together is below the blue power curve, the engine is no overloaded. That only happens when motoring with the engine turning over 2,800-rpm. These are at their heart a Kubota industrial engine which in many cases run at 80% of full rated power continuously 24/7 for years on end. I know of some that are not even shut off to do service and then change the oil while they are running.
My alternator produces over 190A at 2,500-rpm which with my pulley ratio of 2.28 means that I can get my full 160A at an engine speed of 1,100-rpm.