M-25 Alternator Mount Conversion Kit "B/M 256891"
Contents
M-25 Alternator Mount Conversion Kit "B/M 256891"
| If for some reason you haven't changed to the new alternator bracket on your older (1986, early 1987) M25 21 hp Universal diesel engines, DO SO IMMEDIATELY.
I learned the hard way yesterday. I'd bought the retrofit kit from Universal a year ago, and was going to do it "soon." I'd just motored over to a friend's dock for a visit, less than 5 minutes away from our slip. When my friend used the head, he came back and said, "Houston, we have a problem!" He'd noticed oil dripping from the underside of the alternator access door onto the head sole. When we took off the stairs to expose the engine, the old "over the top" alternator bracket had sheared, the alternator was lying back to port dangling from the old fan belt, and there was oil everywhere. As it disintegrated the bracket and alternator had clobbered the oil filter, which spouted oil onto the fan belt and blew it all over the engine compartment. It also nicked the fresh water cooling hose. The oil filter kept the alternator from slamming into the casing of the engine. I got out the new bracket kit, and with generous help from two friends, I removed the old parts, and fitted in the new "underneath" bracket in about three hours. Most of the time was spent adjusting the hose clamps on the new fresh water line which goes under the new bracket, since there is only a very small amount of clearance between it and the top of the oil filter. I also had to use a rubber bicycle tube with a hose clamp as a patch over the dinged fresh water hose, which, of course, was within a half inch of the end of the hose on the new copper elbow. Also, we had to drop the alternator again to move the alternator ground wire further back to one of the other studs since the wire was in the way when it was replaced on its old stud. Lessons Learned:
Stu Jackson, Aquavite #224, San Francisco |
Pictures by Stu Jackson, Aquavite #224 |
Message Board Q&A on the alternator bracket upgrade
Identifying if your alternator mount needs replacement
In the recent copy of mainsheet mentioned upgrading the alternator bracket. I'm not sure mine was ever done, although it hasn't presented any problems yet. I ordered the past tech notes collection, and read the article on the bracket. Unfortunately, the copy quality of the pictures that show the old and new bracket are not good. I wondered if you had a better copy if you could send, or a description that would help me determine if I have the old or new? Dave, Confetti #287, White Lake (Lake Michigan)
Most of us who have read the last several issues of Mainsheet know that the alternator bracket on the Universal Model 25 diesel engine can fail, which can crack the valve cover, resulting in a loss of engine lubricating oil. The manufacturer changed the bracket during 1987, and the current C34 production incorporates the improved engine, although dealers still have some boats with the uncorrected engine. The correct bracket uses an adjustment arm below the alternator. Factory supplied engines will also have "Model 25 XP" affixed to the top of the coolant reservoir. The old arrangement, which is likely to fail in time, has the adjusting arm above the alternator. By the way, the manufacturer does not acknowledge this as a problem, and requires about $115 for the upgrade kit. (NOTE: I paid $95.00 for mine in 1998. It's worth every penny!) Herb Schneider, former C34IA Tech Editor
Stu, Also read your message to Al on the saga of your bracket replacement. Let me give you a couple of thoughts. First the best chafe guard that I've found for around that metal tube that carries coolant above the oil filter is a piece of 1" ribbed black plastic hose (at any marine store -- el cheapo stuff). All you have to do is cut a piece the length that you need and then slice it lengthwise to slip it on where you want chafe guard. The shortest filter that I've found (which I also use) is a Kubota 70000-15241. See the May & Aug 96 issues of Mainsheet for more filter #'s and important discussion. As far as the oil filters the Kabota 70000-15241 was only 1/4" longer than the miniature Fram filters. What I didn't like about the miniature Fram filter was the diameter. It only seated on a small portion of the facing surface of the engine. I also question how much filter material was really in there because of the smaller diameter. Can't remember if it had a clogged filter bypass or not, but don't think it had an anti-drain back valve. Your engine -- your choice.
Another thought. I changed my belt from a 3/8 #395 to a 7/16 #400 which is a "tad" larger & LONGER. If you have trouble and have the space toward the alternator door try a #405 length belt. Ron Hill, APACHE #788
Belt tensioning
As far as belt tensioning - in the dark ages they use a mallet or pry bar. If you go to an auto parts store you can buy a "belt tensioning" tool. It's like a turnbuckle with a left & right thread at a whooping cost of $6-$8! Screw it out till you get the correct tension then tighten the alternator retaining nuts. Easy as pie. Then screw the tool off. Meant to put this in the Mainsheet as a tip.
Don't overtension or you'll be buying a new internal water pump. To get better alternator spacing maybe a washer might help. I replaced all the bracket bolts with longer ones as the holes were threaded all the way thru. I also recommend that alternator upgrades be limited to 90 amp for side loading and spacing. Ron Hill, APACHE #788
Although my boat is newer and has a MP-25XP engine with the bracket below, I wore out two 7/16" wide Gates heavy duty belts on my new Balmar 100 alternator in less than 500 rpm. It was impossible for me to keep adequate tension on the belts. To adjust the tension one must loosen the alternator bracket and the alternator mounting bolt, pull the alternator back and tighten the alternator bolt while keeping tension on the alternator and then tighten the bracket. Having done this several times during a passage while burning hands and arms and having to shut down the engine. I figured there must be an easier way to add tension to the belt and keep it there. I added a turnbuckle between the alternator bolt and the support beam of the engine. The only thing I was afraid of is that by pushing the alternator out, one also pushes on the engine and one could mess up the engine alignment. I have not done this yet, but I really want to. What are your thoughts about this? What size turnbuckle did you use, and how did you mount it? Looking forward to seeing your response or anybody else. Leo Missler, Dutch Lion C34 #1183 (1992)
I did this on the advice of my mechanic who has lots of experience but obviously is not perfect. We did it upon packing up Puff prior to putting her on the hard for the summer (Florida), so I don't have lots of experience with the turnbuckle. However, I used a 3/8" turnbuckle a shorter one. Pressed a nut into the eye of one end and then a couple of big washers and then bolted all that to the port side of the alternator. Screwed in a eye bolt to the engine mount platform and repeated the process on that end. Also put another nut on so I could "lock" it in by running it up against the tube. Wasn't brain surgery and seems to be very solid. It is not on tight enough to change the alignment, I think. It could be a problem if the engine vibrates and the platform doesn't but we will see. It will be a year before I actually try it. Frank, Puff #691
Just a thought about belt tension and the XP-25. If you are just having problems putting normal tension on the belt, then the turnbuckle solution would be ok especially if you relaxed the turnbuckle after tightening up the adjusting bolts on the alt. bracket. Flex mounts are supposed to do just that. I would think that sooner or later the tension of the turnbuckle would either pull things out of alignment or transfer noise and vibration into the engine bed. If you are trying to provide more than "normal" tension then please check out below and confirm this information for yourself. When I was researching putting a high output alternator on "Family Affair" a tech at Maryville Marine, the Universal representative said that they didn't recommend beyond the factory belt tension settings because the front bearing and seal will not put up with a lot of side stress. It seems that the front crank pulley is pretty far in front of the actual front bearing on the block. Belt tension therefore has a lot of mechanical advantage. Much more so than if the crank bearing was right behind the pulley. That front housing is aluminum and full of timing gears. The crank bearing is way back (aft) behind them. Their suggested solution was to add an additional pulley (making 2 belts) on any alternator 100amp or above. They then say you can pull about 5hp off of the stock front pulley. They have the kits available on special order. Ken Dickson, Family Affair C34 #876
