1988 mariner 200hp tach question

[mickab]

hey guys, i have slowly but surly getting this motor lined out with all yalls help. here is one more thing. when the motor was first installed the tach worked fine for a day now it dont work at all. were does the RPM gauge get is signal? and when i took it out this weekend i noticed for the first few mins it was charging over 16 volts. but when i shut it down and started it back up it was back to normal. i dont have a seperate voltage regulator. the two yellow wires from the stator go to the rectifier. on the rectifier one post looks like it melted the plastic around it. so with that is that effecting the tach and or the charging issue?

 

[coastalrichard]

Re: 1988 mariner 200hp tach question

Sounds like your rectifier is toast. A quick search will get you the procedure to test it. The only tool you'll need is a small socket set

 

[mickab]

Re: 1988 mariner 200hp tach question

ok is their an upgrade to the rectifier i could try? seen alot of post for a rectifier/regulator combo and a radio shack item and others. if i can regulate the voltage in some way that would be great. but i guess with just a rectifier its safe to say i have a 9amp stator. and when i say it started charging normal the voltage on my meter is around 12.0 to 12.8. id think thats to low with the engine running but never had a starting problem. and i guess the other thing i should have mentioned is that this boat originally came with a Johnson motor and i took it off for many reasons so i guess id need to figure out also if this tach needs to be on a different setting or if its compatable at all.

 

[coastalrichard]

Re: 1988 mariner 200hp tach question

Mick, with 24 years of age on that motor, I would imagine the stator has been replaced; you should verify what you have. The posts mentioning the RS item is simply a cheaper (some believe more reliable) version of a stock rectifier. If the potting has melted, it's toast.

 

[mickab]

Re: 1988 mariner 200hp tach question

ya it has been replaced and will look closer at it tonight to see if i can find a part# but do those voltage reading sound right to you? i have checked the potting and looks good the only thing like i mentioned was one yellow wire post has melted plastic around it. just wondering if their is an aftermarket regulator to put in place of the rectifier or am i stuck with what i got.

 

[mickab]

Re: 1988 mariner 200hp tach question

ok i in fact have a 9amp stator on this motor and the post on the rectifier that is burnt has the tach wire on it so have ordered the rectifier. but still wondering if im able to put a regulator some were in the system. id like to have that reassurance as i have some pretty expensive electronics and dont wont to fry them. and thanks again for all your help

 

[mickab]

Re: 1988 mariner 200hp tach question

still havent figured out if their is a regulator of some sort to put in the charging system on this engine. any advice would be very helpful.

 

[carholme]

Re: 1988 mariner 200hp tach question

If you look at the parts list which I sent you previously, you will see that there is a V/R available for certain s/ns, though they do not say which s/ns. They say "use on later models" and as yours is a 1988, it puts you in the middle of the pack from 1979 thru 1997

See item 37 under WIRING HARNESS, STARTER SOLENOID & RECTIFIER

Another site lists it as useable on your engine.

However, on your engine, the battery acts as the V/R as it absorbs the load and the cost of a rectifier is far cheaper than $175-200 for the V/R.

Gerry

 

[mickab]

Re: 1988 mariner 200hp tach question

thank you, ya ive been back and forth on that but i think what i will do in the long run is just move to the 16amp stator and use the v/r listed. but got the new rectifier in this morning so ill have to see if all is good. the only time it showed 16+ volts is the day i put the cranking battery on the charger. if i leave it alone and let the engine charge it i stay between 12 to 12.8

 

[j_martin]

Re: 1988 mariner 200hp tach question

88 V6 stock would have a 16 amp stator on it. 9 and 16 are pretty much interchangeable as they both use the same flywheel magnet setup.

12 and a little Volts on the battery is just the normal unloaded voltage, not charging. There really is very little load on the battery when the engine is running. Just oil alert and instruments. Ignition is all independent of the battery.

If you disconnect the yellow wires from the rectifier, and measure resistance between them, it should be low, probably less than 1 ohm, but not shorted. You can also connect an AC voltmeter between the yellow (disconnected) leads and start the engine. It should read about 15V per 1000 rpm of engine speed.

A rectifier will run fine if you maintain your battery. The stock rectifier uses a 15 amp, probably 40 volt small can bridge rectifier, pressed into an aluminum plate and potted in epoxy. Almost guaranteed to fail if anything goes wrong anywhere in the system. Low water in the battery, or a loose connection will usually make them fail on excessive back voltage. I use a 25 - 35 amp, 200 volt or more bridge rectifier available at any electronics supplier and most electronics surplus suppliers. I get em a dozen at a time for about $2.00 each.

You can also wire in one of the 20 amp regulators that come on later mercury engines. They are a design that doesn't waste the excess power as heat, and thus run fairly cool, and are not dependent on the mounting for heat dissipation. They're bigger than a rectifier so you have to find a place to put a small mounting plate for it.

Long story short:
A. Test the AC output of the stator. If it's good (likely) then replace the rectifier, cheap is better in this case, and yer on the water good to go.

B. If it's good you can rig a VR for an upgrade.

C. If it's bad, put on a new stator and either A or B above.

Clean and tighten all your big wire connections.

hope it helps

 

[mickab]

Re: 1988 mariner 200hp tach question

yes that helps a lot thank you. have tested the stator and according to the book its fine, but do have visible damage at the rectifier so will replace that and see what happens. is their a part number for the rectifiers you use? also the later model voltage regulator. don't want to sound like an idiot when i call around to find these items. lol and thanks again

 

[j_martin]

Re: 1988 mariner 200hp tach question

Rectifier is use is 35 amp, 400V GBPC3504. I get them at Mouser electronics, or Digikey. They're about 3 bucks in small quantities.



I use used regulators. They are the 20 amp (2 used in a 40 amp system) 6 wire potted in black. The clear potted 5 wire ones are not as reliable. Here's a picture of one rigged to my XR4, which was a 16 amp rectifier and is now a dual 20 amp regulated system. (one for engine, one for auxiliary batteries) This is from an illustration of splicing, so the yellow wires are not hooked up yet.

 

[mickab]

Re: 1988 mariner 200hp tach question

well to give an update. i received the new rectifier yesterday PN#8M0058226, installed it and all seems well. the tach is now working again and at idle its charging at 12.9 - 13 v at idle and 13.9 - 14 v at wot. now i can move on with the idle and engine height. thank you guys for all your advice. this site is a wonderful thing, thanks again