Perkins 4-236 Alternator

I'm confused about the alternator set up my two Perkins. Original 55 amp unit. (hope to upgrade when $$$ come available) The white power wire goes from the alt to the amp meter on the main panel. Then it becomes a red wire that goes back to the solenoid on the starter. I'm thinking that after the engine starts, the alternator will charge up the starting battery back through the solenoid and battery cable. My problem is how to wire up the ProMariner Isocharger to charge the house bank while underway. House bank is 6 6v golf cart batteries, about 700 amp/hrs total. While underway I use them through an 1500 watt inverter to power the fridge. I bought the Isocharger because it can take two inputs and charge 4 banks of batteries without me having to mess with it. I was thinking of cutting the red wire, and splicing another wire to it and run it to the input terminal on the Isocharger. I'm not sure what consequences might happen. Would I be safer to run a cable from the starting battery positive terminal to the Isocharger input stud, and then a cable from the charger to the house bank? All this heat is frying my logic process.

I changed my 55 amp from 6354.4 Perkins to 100 amp Delco Remy (100 $) 8 years ago.No problems since.For that price you can keep spares aboard.Regarding your later question someone will chime in with info.

Here's a schematic from the instruction manual. Does this help?

http://www.pmariner.com/download.php?file=PROISOCHARGE MANUAL REV VIEW.pdf

Bilgewater, I recently installed an Islocharge. I have a 2-4 unit that combines two alternators to charge four batteries, although I only have three banks. I had the same questions and exchanged messages with ProMariner. On mine I just left all the existing wiring in place and ran a new positive lead to the Islocharge. Make sure you size it for you future upgrade.

Fryedaze - When you ran a new positive lead to the Isocharge, where did it come from?

I connected directly to the positive output post on the alternator. I will get you a picture.

Pictures

FlyWright - Thanks for the pic, I have the manual that came with the unit.
Fryedaze - Looks like I should treat the charging system as two separate systems, the original for the starting battery, then another for the house bank. Seems simple enough.

Iceberg said:

I changed my 55 amp from 6354.4 Perkins to 100 amp Delco Remy (100 $) 8 years ago.No problems since.For that price you can keep spares aboard.Regarding your later question someone will chime in with info.

Click to expand...

We have identical alternators. I have a Perkins 4.108 that was originally equipped with a 55 amp unit. I originally wanted to upgrade to a 110 amp unit, which was available for about $100 through DB Electric.

I'm glad I called Trans Atlantic Diesel and picked their brains a few minutes prior to placing my order for the new alternator. I was informed that due to the placement of the alternator, the engine would be experiencing a significant redistribution of torque toward the side...and far enough from the crank shaft pulley to put excessive strain on it. Installing high amperage units on most Perkins 4.XXX has been known to bend crank shafts over time.

There is a retrofit kit available for Perkins engines that transform the v-belt pulleys and belts to a serpentine system. It is rather expensive, but will allow you to run higher amperages.

In the meantime, I stuck to a 70 amp unit. It was available from DB Electric for less than $100. 70 amp was the maximum Trans Altlantic Diesel indicated for use with a v-belt system equipped Perkins 4.XXX engine.

I know the temptation to purchase a higher amperage unit is strong (as it was for me), but I had not considered the consequences of the disproportionate distribution of Torque likely to affect Perkins 4.XXX series engines. I'm glad I made that phone call before ordering!

Astral Blue - Great info! Thanks for the tip. When I get around to an upgrade, I'll keep the amps to 70 or so. That's still a 27% increase x 2. Bigger is not always better.

"I'm glad I called Trans Atlantic Diesel and picked their brains a few minutes prior to placing my order for the new alternator. I was informed that due to the placement of the alternator, the engine would be experiencing a significant redistribution of torque toward the side...and far enough from the crank shaft pulley to put excessive strain on it. Installing high amperage units on most Perkins 4.XXX has been known to bend crank shafts over time. "

Can anyone explain how load on the front end of an engine could bend a crank? I cant imagine that much torque from an alternator through a belt to the main pulley.
Dave

fryedaze said:

Can anyone explain how load on the front end of an engine could bend a crank? I cant imagine that much torque from an alternator through a belt to the main pulley.

Click to expand...

It doesn't put a permanent bend in the crank, it causes the crank to flex with each revolution and may break if the side load exceeds the manufacturer's specification. The angle of the load is just as critical as the belt tension and pulley overhang.

Since I'm sitting on a Balmar 120A alternator ready to install and had never heard of this before, I called British Marine, my nearest Perkins dealer to confirm or deny this issue. I specifically discussed the side load on the crankshaft pulley.

He was quite emphatic in his reply that the 4.236 and 4.108 engines do NOT have a problem with this, although some other engines do. He didn't specify which engines. He said the 4.236 can run 100% of its rated power off the front of the engine without harm.

I guess we need a tie breaker. I have submitted the question to Perkins via their website and will post the reply here when received.

FlyWright said:

Since I'm sitting on a Balmar 120A alternator ready to install and had never heard of this before, I called British Marine, my nearest Perkins dealer to confirm or deny this issue. I specifically discussed the side load on the crankshaft pulley.

He was quite emphatic in his reply that the 4.236 and 4.108 engines do NOT have a problem with this, although some other engines do. He didn't specify which engines. He said the 4.236 can run 100% of its rated power off the front of the engine without harm.

I guess we need a tie breaker. I have submitted the question via their website and will post the reply here when received.

Click to expand...

An important consideration is that the crank shaft is not a straight shaft that is evenly weighted over the entirety of its length. The weight distribution is of course balanced; and the overall design makes for an even distribution of weight and torque when placed under loads for which the engine is rated.

The point of disagreement between Perkins dealers (i.e., the difference in opinion between British Marine and Trans Atlantic Diesel -- both of whom I have dealt with and have a tremendous amount of respect for) is what constitutes a side load that is capable of compromising the crankshaft.

Here is what we know so far. V-belts are rated for a maximum of 7 horsepower. Staying within 70 percent of its maximum rating (in my opinion) is playing it safe. FlyWright, your 120 amp alternator will draw about 5 horsepower at maximum load. That is 71 percent of the maximum rated load for v-belts. Realistically, you are staying within safe limits as far as the rating of the v-belts go.

The next thing we need to look at is the side load rating for the crankshaft. Perkins has not made any such specification in any of their workshop manuals. I don't even think that's a category for specs from engine manufacturers. We can safely determine how side load impacts the crankshaft by the number of compromised crankshafts via excessive side loads the dealers report. It is purely speculative at this point.

The fact that Trans Atlantic Diesel has designed a retrofit kit that turns v-belts into a serpentine system and has a tensioner calibrated specifically for this rating speaks to the history of compromised crankshafts they have encountered in the past. They wouldn't expend the engineering and fabrication effort if the need didn't exist.

You of course have the freedom to use any alternator you wish with any belt system you are comfortable with. Personally, I feel more comfortable when I stay well within safe boundaries. Repeatedly hearing of incidents of compromised crankshafts from side loads has caused me to weigh the actual cost of the extra 40-50 amps of charging ability. If I needed that extra charging capacity, I would definitely upgrade to a serpentine system.

Another option you can consider is to run the alternator from the prop shaft. I have seen several sailboats with this configuration -- where they have added a second alternator to a pulley they mounted to the prop shaft. It seems like an interesting work-around, but I haven't personally explored it enough to confidently stand behind it.

The alternator I hope to install would be derated to 100A by the smart regulator to remain within the 110A limits of my current 1/2 inch v belts. I have to admit that I find it hard to believe that any side load transmitted through a properly sized and tensioned 1/2 inch v belt would damage the crank before breaking the belt. But apparently it does happen when overtightened.

The problem according to TAD here is the high output alternators (in excess of 150A) will cause belt slippage and excessive dust with the standard 1/2 inch belts. Operators commonly OVERTIGHTEN the belt to stop the slippage and cause failure of the crankshaft at the #1 journal. The serpentine belt/pulley kit is intended to address that problem of damage through overtightening.

Balmar recommends nothing more than 110A on a 1/2 inch v belt.

'We recommend a minimum 3/8” belt (measured across the back of the belt) for alternators up to 80-amp output. Minimum belt width for alternators up to 110 rated amps is 1/2”. Any alternator larger than 110-amps will require dual belts, or multi-groove serpentine belts for optimal performance, as well as acceptable belt life."

My understanding is that the TAD and Balmar serpentine belt kits are intended to address the belt slippage with large (>110A) alternators which in some cases leads to overtightening the belt tension which then can cause the excessive sideload. IMO, a properly sized and adjusted belt does not induce these excessive loads. But I'll wait for the official word from Perkins on this matter before continuing with my plans to install the 120A/100A Balmar.

Interesting discussion. We had a Perkins 4-108 with a 120 amp Balmar alternator and added a serpentine belt after we had excessive belt slippage, using a single a single belt. At the time (late 90's), Balmar was pushing the serpentine belt as an alternative to duel belts. They sold the 3 pulleys and belt as a kit for the 4-108.

FlyWright said:

The alternator I hope to install would be derated to 100A by the smart regulator to remain within the 110A limits of my current 1/2 inch v belts. I have to admit that I find it hard to believe that any side load transmitted through a properly sized and tensioned 1/2 inch v belt would damage the crank before breaking the belt. But apparently it does happen when overtightened.

The problem according to TAD here is the high output alternators (in excess of 150A) will cause belt slippage and excessive dust with the standard 1/2 inch belts. Operators commonly OVERTIGHTEN the belt to stop the slippage and cause failure of the crankshaft at the #1 journal. The serpentine belt/pulley kit is intended to address that problem of damage through overtightening.

Balmar recommends nothing more than 110A on a 1/2 inch v belt.

'We recommend a minimum 3/8” belt (measured across the back of the belt) for alternators up to 80-amp output. Minimum belt width for alternators up to 110 rated amps is 1/2”. Any alternator larger than 110-amps will require dual belts, or multi-groove serpentine belts for optimal performance, as well as acceptable belt life."

My understanding is that the TAD and Balmar serpentine belt kits are intended to address the belt slippage with large (>110A) alternators which in some cases leads to overtightening the belt tension which then can cause the excessive sideload. IMO, a properly sized and adjusted belt does not induce these excessive loads. But I'll wait for the official word from Perkins on this matter before continuing with my plans to install the 120A/100A Balmar.

Click to expand...

To be honest, my conversation with TAD was the first time I heard about this issue. It prompted me to look further into it, which presented me with enough evidence to think twice about taking the path I was intending.

I'm very interested in hearing what position Perkins takes on this since there seems to be differences regarding the position authorized Perkins dealers are taking on the issue.

Do keep us posted with how your installation goes; and how it performs over time. I honestly don't think a 100 amp alternator is going to give an excessive side load. This is especially the case if the belts are not over-tightened.

While I might have personal reservations about it, I find myself being overly conservative when it comes to testing the limits of any mechanical equipment. But that's my psychosis...and I'm sure there are 12 step programs and psych meds that can help me overcome it.

Do keep us posted with how your installation goes; and how it performs over time.

I'll do that, Ed. And welcome to the forum. BTW, I keep my boat down the road from you and used to berth at the Sacto Bay Club.