Happy_Jack
Seaman Apprentice
- Joined
- Aug 13, 2009
- Messages
- 41
Just a note of encouragement for those confronted with charging issues/erratic tach operation, who are considering changing the regulator/rectifier.
I have a 1987 Johnson 90hp, with TnT with the water cooled, 35amp reg/rect unit.
My tach was erratic (went to about 2k rpm, then dropped to 0)
A multimeter connected to my battery (cables connected of course) showed battery voltage (about 12.4 vdc) starting the engine made no difference in this reading.
I had a parts motor I picked up for $50 (I bought 2 parts motors and used parts when I refurbished my boat/motor over the past winter) I pulled the reg/rect off that motor (same 35 amp rated unit) and did the "bench test" prescribed by the CDI electronics website. After ohming out the wires on the used (but looks brand new) unit from the parts motor, I was confident that it was a good, serviceable unit, but I WILL say they want to see 25 mega ohms resistance from the red wire to ground (very high) I was reading about 2.6 M ohms, but ONLY on the M ohms scale, anything on ohms or K ohms did not read at all.
I also did the same bench test on my existing unit, it failed miserably.
Before I removed the old one, i also did Joe Reeves abbreviated check to determine if the tach was bad, or the reg/rect, it pointed to the reg/rect, because the tach worked good when the grey wire was connected to the yellow/grey wire and engine running..
I did the swap using a new gasket, flywheel removal was of course necessary.
I carefully connected all of the wires, ONE NOTE: the newer part number (I do not have it in front of me), but there were several supercedes to the original part number which was on the motor when I got it, do NOT have the purple wire present. the original one did..I researched this, and found that at some point it was removed, and no longer used when they made the units.
So I hooked up all the wires, (except the non-existant purple one) and put it all back together, including torqueing the flywheel to 105 foot pounds i believe, then re-connecting the battery wires tight with nuts & lockwashers, and fired it up. My tach seemed to work, and the charging voltage showed 13.2 as I recall, I revved it up a couple times, since it needed to hit 2k rpm before it fell off, and it seemed fine.
Not wanting to over-rev the motor on the muffs, I took it to the lake, and took it for a spin, the tach works great, the charging system is working, and the upper portion of the block next to the reg/rect seems cooler to the touch.
So if you suspect your reg/rect, use the great tutorials here posted by Joe Reeves, and research your part numbers, amp ratings for your regulator/rectifier, and go for it. I just ran the boat (17' Whaler restored over the winter) hard on our vacation, and tubing, fishing, swimming, etc were enjoyed by all, with no issues thanks to all who post here for some great information and advice.
Lots of people i talk to think the "older" (late 1980's) V4 motors are disposable, I say that's fine, give them to me, this motor runs like a top, idles like a sewing machine, and pumps like a fire truck. I have spare parts everywhere on the parts motors I bought for next to nothing. These things are GREAT.
Happy Jack
I have a 1987 Johnson 90hp, with TnT with the water cooled, 35amp reg/rect unit.
My tach was erratic (went to about 2k rpm, then dropped to 0)
A multimeter connected to my battery (cables connected of course) showed battery voltage (about 12.4 vdc) starting the engine made no difference in this reading.
I had a parts motor I picked up for $50 (I bought 2 parts motors and used parts when I refurbished my boat/motor over the past winter) I pulled the reg/rect off that motor (same 35 amp rated unit) and did the "bench test" prescribed by the CDI electronics website. After ohming out the wires on the used (but looks brand new) unit from the parts motor, I was confident that it was a good, serviceable unit, but I WILL say they want to see 25 mega ohms resistance from the red wire to ground (very high) I was reading about 2.6 M ohms, but ONLY on the M ohms scale, anything on ohms or K ohms did not read at all.
I also did the same bench test on my existing unit, it failed miserably.
Before I removed the old one, i also did Joe Reeves abbreviated check to determine if the tach was bad, or the reg/rect, it pointed to the reg/rect, because the tach worked good when the grey wire was connected to the yellow/grey wire and engine running..
I did the swap using a new gasket, flywheel removal was of course necessary.
I carefully connected all of the wires, ONE NOTE: the newer part number (I do not have it in front of me), but there were several supercedes to the original part number which was on the motor when I got it, do NOT have the purple wire present. the original one did..I researched this, and found that at some point it was removed, and no longer used when they made the units.
So I hooked up all the wires, (except the non-existant purple one) and put it all back together, including torqueing the flywheel to 105 foot pounds i believe, then re-connecting the battery wires tight with nuts & lockwashers, and fired it up. My tach seemed to work, and the charging voltage showed 13.2 as I recall, I revved it up a couple times, since it needed to hit 2k rpm before it fell off, and it seemed fine.
Not wanting to over-rev the motor on the muffs, I took it to the lake, and took it for a spin, the tach works great, the charging system is working, and the upper portion of the block next to the reg/rect seems cooler to the touch.
So if you suspect your reg/rect, use the great tutorials here posted by Joe Reeves, and research your part numbers, amp ratings for your regulator/rectifier, and go for it. I just ran the boat (17' Whaler restored over the winter) hard on our vacation, and tubing, fishing, swimming, etc were enjoyed by all, with no issues thanks to all who post here for some great information and advice.
Lots of people i talk to think the "older" (late 1980's) V4 motors are disposable, I say that's fine, give them to me, this motor runs like a top, idles like a sewing machine, and pumps like a fire truck. I have spare parts everywhere on the parts motors I bought for next to nothing. These things are GREAT.
Happy Jack