Red Check Engine Light

Ok - So I'll give you an update on my fix:  Ski 176 drives great and Red Light off after the oil switch replaced; ready for another 25 years and hundreds of hours!   Woot!

You already have the new switch, just put it in.

That poor old "original" switch cycled itself every time you turn the engine on and off.

if your oil is cruddy enough to plug the old switch, you probably have other things to worry about

This version of the TRB diagram is probably the closest you'll get for the engine wiring with your PMGR starter.

The wiring for the Red check engine light isn't shown, since it wasn't on his boat probably 
 

Thanks for the info KENO!

I was on Nautique Parts website looking at the switches mentioned in this thread and I saw they sell a temp/oil pressure switch and buzzer kit for about the price of one of the other switches. I need to know the thread size on the temperature switch before I can order it but I'm thinking about going that way along with an alarm indicator light they sell. They also sell the oil pressure tee fitting, so conveniant! Any reason I shouldn't get the alarm kit and just stick with the parts you listed instead?

Kit SKU# 6257 https://nautiqueparts.com/alarm-buzer-low-oil-overheat-system/

And don't forget to use the not too well publicized PND discount code for a 10% discount on the order 

It looks like #1 has a tan wire so it's the temperature sending unit and #5 has a green wire so it's the high temperature switch.

It sounds like the oil switch would pretty definitely be the problem based on your description.

The oil switch is part # R020015A like mentioned earlier.

The temperature switch is part # R020014............there's no A on the end. The one with the A on the end would be for the gt40 switch location which is different than your location.

I'd pull the wire from the oil switch, tape the end so it can't ground itself on the block and take the boat for a ride  Your light won't come on when you turn the key to the Run position and it shouldn't come on at any time if the oil switch is the issue. If it does come on during the drive, that would point to the temperature switch.

Then you can decide whether you want to replace both switches or just the bad one.

I wouldn't mess with either sender if you have good, normal oil pressure and temperature readings on your gauges.

PS.........if you hit the space bar between pictures, they won't all run together 

On a gt40 they turn on the dash light and at the same time, tell the computer to put the engine in SLOW mode often called limp mode, but they don't kill the engine.

On the carbureted engines with the same switches, they'll turn on the dash light and nothing else. Then you look at your temperature gauge/oil pressure gauge to see if you have normal readings with a switch malfunction or an actual problem.

For your 1980, with a little wire and a couple of switches, a tee for the oil switch, a light and some connectors and a horn if you were so inclined, you could make your own setup for a whole lot less than the cost of the PCM labeled switches at Nautiqueparts. 

If it's in the hole by #5 cylinder (green arrow) it has 3/8 NPT threads and takes part number R020014

If it's in the hole by #1 cylinder right behind the thermostat housing (tan arrow) it has 1/2 inch NPT threads and takes part number R020014A

Switch in one hole, sending unit in the other

And like Air206 said the oil switch is R020015A. It's the only one they sell these days, no other choice.

I think the rest is up to you and Nautiqueparts