1979 90HP Mercury inline 6 has no spark

[ellis@cedarwoodco.com]

Hey folks,
I pulled my boat out of winter storage and attempted to start the moter and have no spark. I checked spark plugs and did the "screwdriver in the wire" thing...nothing. I've messed around with ignition problems on car engines some but when it comes to outboardsb I'm lost. I'm hoping it's something small and easy, because it ran great when I parked it last fall. However, one mechanic said I might need a new stater? and/or powerpack. And with that old of an engine, it's hardly worth it. Is that true? Thanks for any help in advance.

 

[OldMercsRule]

Re: 1979 90HP Mercury inline 6 has no spark

A good running 90hp inline is a great motor. It may be a stator, (does not a 1979 have a distributor as my 115 does{?}, [if so: ya may have a bad 'trigger'; the trouble shoot proceedure is here on iboats somewhere if ya search]), but check out the rest of the engine out before fixing it. Check compression n' the lower unit et al. You could always spend $10,000 + to put a much heavier n' much fancier, (with lots o' whistles n' bells) new engine on yer boat. 'Course the boat will not go as fast n' you will really cry when the new one is outa warenty n' lays down on ya. That said :I guess I should be positive, and welcome you to iboats. My name also indicates that I luv the kinda motor ya have, n' don't let anyone talk ya into tryin' a "float test" on her! If ya live near Seattle and wanna get rid of the ol' "boat anchor" let ol' Murky know please! JR

 

[duff]

Re: 1979 90HP Mercury inline 6 has no spark

old merc where abouts in the seattle are you? just wondering if you are close enough to me if you only work on your own boats or if you work on them for a living? (if you do not was to post where you live please email me) (salmonslayer75@yahoo.com) I have a1979 80hp merc it does not have a distributor just stator trigger and switchbox. that is what my problem was when mine would not spark. if you see any of the insulation cracking and falling off replace them. not really that hard to replace the stator,trigger, and switch box. can be done for under 350 if you look around for the parts and do the work yourself.

duff

 

[ellis@cedarwoodco.com]

Re: 1979 90HP Mercury inline 6 has no spark

Ok, so now I'm confused. I was looking at wiring diagrams on www.maxrules.com and I can't make it match up to my motor. I thought it was a '79, but it has a distributor. I don't think it has a coil for each cylinder like the '79 diagram shows. The '78 diagrams make a lot more sense, so maybe mine's a '78? I'll see if I can find the serial number, etc. Maybe that'll help.

 

[OldMercsRule]

Re: 1979 90HP Mercury inline 6 has no spark

old merc where abouts in the seattle are you? just wondering if you are close enough to me if you only work on your own boats or if you work on them for a living? (if you do not was to post where you live please email me) (salmonslayer75@yahoo.com) I have a1979 80hp merc it does not have a distributor just stator trigger and switchbox. that is what my problem was when mine would not spark. if you see any of the insulation cracking and falling off replace them. not really that hard to replace the stator,trigger, and switch box. can be done for under 350 if you look around for the parts and do the work yourself.

duff

Hey Duff, I live in Bothell n' work in Bellevue in the retail food business. I'm not a mechanic, (other then a relatively fearless back yard type mech. with a set of tools). I just luv the old inlines, power to weight is second to none. They are also fairly cheap, simple, and interchangable, (just like a small block Chev)! I work on some of the things that are fairly easy to do. I was mainly lookin' to collect a lower unit for my 1978 115. My 1979 115 has a distributor so I'm not sure what you found in the way of schematics, I think 1980 is when the distributer went away. I have a 1981 115 w/o dist. I'm also lookin' to collect a PT unit or two for two of my non PT inlines. I generally look for the six cylinders. Thanks JR

 

[Chris1956]

Re: 1979 90HP Mercury inline 6 has no spark

If your motor has a distributor, and no spark, the first thing to do is to disconnect the blue mercury switch on the dist side of the switchbox. If still no spark, check to make sure you have +12V on the red wire on the switchbox at all times, and +12V on the white wire on the switchbox, when the key is on. Here is the troubleshooting procedure(courtesy Clams Canino):
MERCURY BATTERY-POWERED CDI TEST
FOR DISTRIBUTOR MODELS

This test is for the 332-2986 switchbox used from 1967-1978 on all the inlines.

This test assumes your coil is good (most all are).

DISCONNCT BATTERY

1. Turn off ignion
2. Disconnect all 3 wires on the distributor side of the switchbox.
3. Remove the HV lead from the coil to the center cap (remember it unscrews
from cap)
4. Reconnect that HV center lead to the COIL side only.
5. Position that HV lead about about 3/8" from ground (block, shrouds etc)
and find a way to hold it there.
6. Jumber the brown and white terminals on the dist. side of the switchbox
together.

RECONNECT BATTERRY

7. Check that you have +12 V at red terminal.
8. Turn on ignition and verify +12V at white terminal (on red terminal side)
9. Touch the black terminal to ground - unit should cause spark each time
you touch ground.

If that passes and it won't fire at all, suspect the trigger

 

[ellis@cedarwoodco.com]

Re: 1979 90HP Mercury inline 6 has no spark

Thanks for all your help, guys...especially Chris1956. Your post looks like exactly what I was looking for, except....now it works!....and I didn't do anything except tow it around looking for a rumored local boat mechanic.
This evening I looked at it again and I have spark...bright blue and strong. Engine fired right up and runs good. Look out lake.

Still have a little nagging question in my mind...What was wrong and when is it going to happen again? Out in the middle of the lake?

Do ya'll think it was a loose wire of some kind or what?

Summary of scenario:

1. Bring boat out of storage after having run great last season and having been winterized more or less...

2. Try to start it this morning.

3. Absolutely no spark in plugs or wires. Didn't check anything else.

4. Get all scared about possible worst-case scenarios...

5. Tow it around a couple miles bumping in and out of gravel roads this afternoon.

6. Check spark again this evening. Bright and blue.

7. Engine fired right up and runs great.

What do ya'll think?

Thanks again.

 

[ellis@cedarwoodco.com]

Re: 1979 90HP Mercury inline 6 has no spark

One other thing I forgot...What's the most reliable method of identifying the year on a motor?

The original owner says it's a '79 and I guess he should know.

And according to one website the serial number says it's a '79.

But the wiring diagrams I got from maxrules.com only made sense if it's a '78.
Also chris1956, the 332-2986 switchbox is the one that's on it and you said they're on the '67-'78 inlines. Are they on those models only ?

 

[OldMercsRule]

Re: 1979 90HP Mercury inline 6 has no spark

There is a mercury switch on the side of the switchbox. Check that as it grounds the motor when it is tilted up. Also pull the cap and look for moisture. The Serial number is on the motor bracket at the base of the power head as you face the engine. My 1979 115 has a distributor. There is also a serial number stamped on the block where the two sections bolt together. JR

 

[Chris1956]

Re: 1979 90HP Mercury inline 6 has no spark

You can find out the year with your serial number. However, the serial number is more important than the year, since parts are organized by the serial number.

On your intermittent spark situation. You might like to check the rubber molded plug at the motor for corrosion. The center wire is usually the ignition wire. Make sure the pins are clean and the connectors are also clean.

 

[Russ Keeler]

Re: 1979 90HP Mercury inline 6 has no spark

[whisper uid=90437]

Enter private whisper here
check wiring harness inside motor area. Old mercury harness are famous for the insulation around wiring cracking and falling off.Just moving a wire around can make it short out(no spark) or fix spark. You can get a whole new harness for around 100.00 comes with directions, easy to install.Russ




[/whisper]

 

[Nohfire53]

Re: 1979 90HP Mercury inline 6 has no spark

I have the same motor, it is a '79, but the type II distributor ignition system is a hold over from '78, for all intents and purposes it is a 1978.
Make sure you buy the Selocs manual, it covers all manners of motors from the '70s and has plenty of pics to match up your motor.
Wires popped loose or losing insulation are a big problem with a 30 year motor, I would make sure I triple check all the fittings and dab a little dialectric grease on the bulk of the connections. I did that and haven't had a problem.

Also, the selocs helps you figure out what parts you need by the pics, I am not sure my serial either so we are kinda in the same boat!!!! Too much huh?

Good Luck!

 

[ezmobee]

Re: 1979 90HP Mercury inline 6 has no spark

Nohfire, please look at the post dates before you reply. This thread 4 years old!