Mercury 90HP-1985 Tower of Power How to install new rectifier -old one is different

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Imjus4u2nv

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I have a 90 hp mercury tower of power, year 1985.

I have been having issues charging and after reading the forums decided to try swapping out the rectifier since it is cheap and the most likely problem.
The new rectifier looks like a standard three terminal (with the metal frame on the back that grounds to the engine).

I am trying to locate the old rectifier and can't seem to find it. I looked at my repair book and I believe it may be an old round rectifier. Does anyone know for sure where the rectifier should be located in this engine, or the best way to find it?
Also, if the round thing is the old rectifier, anyone know which wires go where (I was hoping it would be the same as the replacement making it fool proof but no luck).

Any help is greatly appreciated- Thanks All!
 
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Imjus4u2nv

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Re: Mercury 90HP-1985 Tower of Power How to install new rectifier -old one is differe

Thank you for your response, I will be down to the boat later this week and will see if that is where it is. From looking at my Seloc repair manual, I am pretty sure my boat as the old style of rectifier (plate-rectifier). I will upload some photos this weekend, as I already bought the rectifier for a 1985, however I am not certain it is a 1985 (just what the previous owner told me). I am unable to locate the S/N- any advice?
 
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Laddies

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Re: Mercury 90HP-1985 Tower of Power How to install new rectifier -old one is differe

The
 
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Imjus4u2nv

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Re: Mercury 90HP-1985 Tower of Power How to install new rectifier -old one is differe

Hi Gerry,
Thank you for taking the time to help me out (I am learning slowly but surely).
The picture you provided finally allowed me to find the S/N - which is A968445. So it is NOT a 1985 and I believe is a 1986.
I looked at the engine today, and it appears the rectifier should be on the same side as the S/N all the way at the top, under the top cover for the engine (I also saw a yellow wire which make me optimistic). Do you know if the rectifier will be located under the top cover? I will take it off this weekend but did not have extra hands to catch any falling bolts etc.
Now that I know the boat is a 1986, I checked the website/link your provided for Crowley and it appears the 1986 and 1985 have the same part number for the rectifier (8M0058226).

I bought a rectifier off ebay for $25 which I am hoping and believe is the right part- the description is below:
Mercury Marine
Outboard

Replaces:
Mercury Marine
62351A1, 62351A2, 816770, 816770T

Notes:
OEM(s): Mercury Marine
Number of Diodes: 2
Diode Amps: 25
Unit Polarity: Negative
Includes Brush Holder?: No
Includes Capacitor?: No
Includes Trio?: No
Notes: 3-Wire Hookup
Application: Mercury Marine Outboards


I also found this chart on another ebay page which shows older model rectifiers and a higharchy of replacement parts(chart wont copy and paste- see link- Mercury Mariner Voltage Regulator Rectifier New 816770T 8M0058226 | eBay ).

"Brand new, genuine Mercury rectifier, part number 8M0058226. This is a factory original equipment part, not aftermarket. Supercedes from and is interchangeable with prior part number 816770T.

SKU# 8M0058226





8M0058226

816770T

816770

62351A1

62351A2

70350A1

70350A3



49184

"

Do you think I have the correct rectifier? Thanks again- JARED
 
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carholme

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Re: Mercury 90HP-1985 Tower of Power How to install new rectifier -old one is differe

That s/n comes up as:

MERCURY - ( 90 H.P. (1986 ))
Serial No: 0A968445 Model No: 1090726

Parts List for model 1090726:

90/115 H.P. (INLINE) - Mercury, Mercruiser, Force, etc. Parts Lookup

AS you have already seen, item 7 under SWITCH BOX AND STARTER SOLENOID, p/n 8M0058226 is correct.

The service manual you require is p/n 90-86134--4

Here is one at half price:

Used 92 Brunswick Models 75 80 85 90 115 140 150 IN Line Service Manual | eBay

In the interim, here is a link to the condensed version of the Clymer manual which will help you get started. Download it soonest to your computer as the link is short lived.

Small Engine Repair Reference Center Home: MERCURY - MERCURY IN-LINE SIX-CYLINDER MODELS (1969-1988).

You will see a rough picture of the rectifier location in Fig, M14-27 on page 310.


Hope this helps.

Gerry
 
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Imjus4u2nv

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Re: Mercury 90HP-1985 Tower of Power How to install new rectifier -old one is differe

UPDATE-
I was able to locate the rectifier. It is on the starboard side of the engine (the right side of the engine is looking at the boat from the back) all the way at the top under the top hood of the engine (the hood I thought was bolted on but it just comes off the top). I replaced the rectifier unfortunatly still no charge. I am going to test the new rectifier to see if it blew already or if it is the stator. My RPM's are still jumping all over the place.
I have been having other issues with the engine boggin while trying to get on plane- I fixed this (at least I thought) by changing the sparkplugs which when i removed the old ones realized they were not in tight at all (was able to take two out by hand). Did a compression check while I had the plugs out at was at 119 or 120 for all 6 cylinders- good to know compression is good. The spark plugs were 'oily' and wet which leads me to believe I am running to rich and burning to much gas. After changing the plugs she ran great! Next time out, runs great for about 15 minutes then stall, had a hard time getting it back started, finally did but kept stalling- hoping this is because I let the gas run way to low and maybe sucked some crap from the gas tank up. When I got back to the dock (limped in) I got her to start and run without stalling and was able to get in an out of gear/reverse with no issues so hoping it was a just a clog and it cleared.
I will keep updating in case someone has any suggestions or in the hopes that I will solve these problems and provide information for others with similar issues.
 
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Imjus4u2nv

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Re: Mercury 90HP-1985 Tower of Power How to install new rectifier -old one is differe

UPDATE
Boat is fixed, mostly
Charging problem resolved- insulation to yellow wire on stator fell off, shorting against engine. Fixed the wire, installed new rectifier and it is now charging.
Also engine bogging issue is fixed- not sure which fixed it, but drained the carb (screw on bottom Port side comes out and drains the gas out- mechanic recommended this). I think the problem stemmed from a loose wire going from the stator to the switchboxes(?). It was so loose, had to tighten it down and ever since the boat is running great.

PROBLEM-tach was working with rectifier I purchased off ebay but was not charging, ordered the correct rectifier thanks to Gerry, and she is charging but now the tachomete won't work. When I was messing with teh rectifier off ebay, at one point I turned my battery off while the engine was running (wasn't thinking) and saw my volts jump up to about 20v. SInce then my tach has not worked- can you blow a tach? I am going to try switchign to other side of the rectifier and trace the tach wires to see if an inline fuse somewhere.
 
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oldman570

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Re: Mercury 90HP-1985 Tower of Power How to install new rectifier -old one is differe

There is a chance that the tact did blow depending on the manufacture and time that the high voltage was present. Electronics are very touchy when it comes to high voltage. The CDI web site explains this to some extent. I use their rectifier/regulator units if I have expensive accessories as fish locators or marine radios on the boat, so the voltage doesn't get high enough to do damage. JMO
Oldman570
 
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