90a rectifier issue

[Ausmat]

Hi guys
i have found that I have a faulty rectifier on a df 90a, I have swapped the rectifier and the motor is working again and charging at 14v at idle . Is there anything I should check that would of caused the recifier to die?
also I have twin motors one idles at 43c and the other at 55c the one that's at 55c is hotter to touch. Is this an issue?
thanks for your help.

[artdf175]

how old are these? number of hours ?
when were the impellers last replaced?
thermostats checked?
a little more information please

[Moonlighter]

There are different reasons why the regulator rectifier fails. One of the top causes is heat, so make sure your engine cooling systems are up to scratch. If you change water pumps, include the housing as well, and also check those thermostats as it sounds like the cooling system on at least one of your motor could do with some attention. I would suggest a water pump service at least every 18 months - if nothing else, it makes you drop the leg and means that those gearbox bolts dont freeze up and the output shaft gets greased so it doesnt jam.

Other causes for a dead regulator rectifier center on the battery. Ground connections are important for good voltage, and if there is faulty voltage, the regulator rectifier can run hot. Bad grounding, corroded battery connection (cables too) and poor or loose battery connections will cause faulty voltage. Main battery switch is also something to check as internal corrosion is pretty common and hidden from view. So these are areas to check.

[Ausmat]

Thanks for the advise guys. What should the idle temp be?

[Murray]

Thanks for the advise guys. What should the idle temp be?

From a 2009 DF90A service manual. Thermostat operating temperature 58-62C (136-144F)

[pniksnut]

moonlighter is wright about bad connections . this year only i had 3 broken regulators in the shop all down to bad connections and corrosion in the main battery switch. the engine temp can be an issue. normal is around 60 degr. C with a 60 degr thermostat. if it stays colder your thermostat is not working correct. there is an hotter thermostat available (70 degr. C) but that is only for use when you have an oil problem. when an four stroke stays to cold there will be an fuel bildup in the oil and the oil level will rise. 43 degr. is certainly to cold.

[wilbur1]

I was told to install the hotter [70] degree thermo cause I idle a lot on No-Wake lakes I fish and some trolling.

[Moonlighter]

moonlighter is wright about bad connections . this year only i had 3 broken regulators in the shop all down to bad connections and corrosion in the main battery switch. the engine temp can be an issue. normal is around 60 degr. C with a 60 degr thermostat. if it stays colder your thermostat is not working correct. there is an hotter thermostat available (70 degr. C) but that is only for use when you have an oil problem. when an four stroke stays to cold there will be an fuel bildup in the oil and the oil level will rise. 43 degr. is certainly to cold.

Agreed!!

Those main battery switches can be bad news. Mate’s boat/motor caught fire when his switch basically fell apart internally. Luckily he was able to pull the leads off the battery pretty quick and got it under control. Insurance paid for motor harness and ecu repairs. I have also seen and heard of quite a few cases where the main battery cables had got corrosion internally. Bad news.

The summary of recommendations for the OP is:

1. do a really thorough check on those battery connections in all areas as mentioned earlier. Especially the main switch. By check - we mean - disconnect each connection, inspect, clean, reconnect and tighten properly. If any doubt about the main switch - just remove and replace it.

2. Drop the legs on both motors and do a full water pump kit including housing. Make sure to grease the splines of the main output shaft when reassembing. Gearbox oil change at same time. Do this every 12 or 18months. That way you will be ale to get it off before bolts etc have a chance to seize up and give you a major headache!

3. Check and (probably) replace both thermostats, especially if they havent been done before. In our hot Aussie temps, stay with the standard temp models as fitted.

[Ausmat]

Hi guys,
thanks for the advise,
I found the port motor thermostat stuck open so has been replaced temp now 62c, the negative termail on battery 2 had a very loose terminal which has been tightened.
i tested the stater as per service manual and .2 ohms on all 3 connections and the reading matched the other motor. So fingers crossed all sorted.
once again thanks for the help