Melted Voltage Regulators on 1991 Mercury 200XRi

[88MCPS200]

Ran my boat approx. 40 miles at various speeds yesterday with air temperatures reaching the upper 90's. Motor ran nice and cool with the refreshed water pump. When I put the motor in neutral approaching the dock for lunch the motor died. Couldn't get it to start except with it set to part throttle in neutral but it would die again when brought back to idle. Noted the smell of electronic death so pulled the engine cover and saw some goo in the lower motor cover and then noted the Voltage regulators burned up melting the epoxy backsides. My 1991 200XRi is un-modified and has 2 Voltage Regulators.

I'll take a look at the Stator for any signs of burns but is there anything else I should check out? I have a new starting battery that I put in last month after the previous starting battery burst while on the maintainer. Also experienced an overheat three weeks ago where the water pump gasket somehow got pulled into the impeller. I did note during yesterday's outing that the Tachometer started acting erratically (basically on/off/on/off) leading me to think that it's just the Voltage Regulators.

As for replacement Voltage Regulators what would be preferred, OEM Mercury, CDI or something else. I'm leery of the other aftermarket brands given the significant price difference between the Mercury/CDI units and the other aftermarket options.

Apologies for the long post but wanted to give perspective on events leading up to the Voltage Regulators' demise.

Thanks,

Mike B

[tlwjkw]

guess you're one of tha lucky ones!.. most '91's had tha famous water cooled reg/rec...

tha cheapies are jus "pot luck".. know sum that are still workin'.. oem and cdi seem ta be tha better choice.. jus be sure ta check stator output!.. one thing ya need ta do (unless its still got tha 4 terminal block) is cut tha bullet connectors off then solder/heat shrink tha joints.. that will help with an over heat at tha connector joints..... a common problem with tha two reg/rec stuff.........

[David - WI]

Scroll down to SH847 "Series"-type regulator (although I would read the whole page): https://www.roadstercycle.com/index.htm

Better than the Merc stuff in every respect and about half the cost of CDI parts.

Further down is a connector kit if you don't want to splice wires (put the connectors on your stock wires) and mounting brackets if you need one. (Also need a special wire terminal crimper for the connector kit.)

[88MCPS200]

Thanks for the info, mine has the bullet connectors. Looks like I can get the CDI VRs for under $200 each vs another $50 each for the Mercury units.

[88MCPS200]

Thanks for the info on the SH847. Will research those vs. the CDI units. Looks like the units with the mounting brackets would be a wash.

[88MCPS200]

Made a visual inspection of the Stator and it appears to be fine. Is there any way to test it without the motor running or will I need to install the new VRs and test it running?

[David - WI]

Thanks for the info on the SH847. Will research those vs. the CDI units. Looks like the units with the mounting brackets would be a wash.

You only need on SH847.

[88MCPS200]

You only need on SH847.

David, so I would only use one SH847 when I currently have two Voltage Regulators?

[David - WI]

David, so I would only use one SH847 when I currently have two Voltage Regulators?

Yes, they are actually 3-phase... so there are 3 separate 50 amp circuits. You would use two.

[88MCPS200]

Yes, they are actually 3-phase... so there are 3 separate 50 amp circuits. You would use two.

Thank you for the clarification. Will likely go this route. Like that they have the heat sinks.

[David - WI]

Yes, basically this is a 100 amp regulator for a 40 amp charging system. The cool thing is that rather than just shunting the excess voltage to ground... these disconnect (for milliseconds) so the stator runs cooler and uses (a bit) less horsepower.

Also (obviously?) this is the rectifier, too.

[88MCPS200]

Yes, basically this is a 100 amp regulator for a 40 amp charging system. The cool thing is that rather than just shunting the excess voltage to ground... these disconnect (for milliseconds) so the stator runs cooler and uses (a bit) less horsepower.

Also (obviously?) this is the rectifier, too.

Looking at the SH847 online I'm seeing it has 3 Yellow Wires while my Stator has 4 Yellow Wires, how would I account for the extra wire from the stator? 2 go to one Voltage Regulator and the other 2 connect to the 2nd Voltage Regulator. Don't want to let the smoke out of other components due to incorrect wiring on my part.

Thanks.

[David - WI]

522304

(If you had 3 stator circuits... yellow wire #5 & #6 would connect from A to C.)

[88MCPS200]

Thanks for the diagram David. I was thinking along those lines but wanted to assure proper wiring. I greatly appreciate all the help. Now to order my parts.