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Stop switch continuity merc 9.8 1979

B

b521

Regular Contributor
MERC 9.8 CIRCA 1979 SN 5453792
Got another spare motor on a boat flip, This engine was not suppose to be runable, However I got it running fine. Now It was going to be next years project, as I need a few parts etc. It has this gawd awful stop switch on it, It says made in china on it, It does not look like anything on the engine diagram. this thing is as big as a sparkplug , so I was going to search around and find a well built enough spring loaded button switch in spare time to replace it. rather than pay 52 bucks for a merc one,, Before I tucked it away I decided to check continuity to make sure that it is a push in that closes the circuit and vice versa. Just my luck the switch has a continuity at rest of 2 ohms(so there is something making some kind of partial connection in there
)and full continuity when you press the button in. Is this the way it is suppose to work. This motor has the black switchbox and it appears that someone replaced it once and the wiring is a real jumbled mess, he has some connections taped with duct tape and partial pieces of wire taped to the connections , example, he has two black wires connected and he has a 2 inch piece of brown wire taped to that connection,but not connected to them ,, which i assumed means that one of these ends would be a brown wire under normal circumstances,) so maybe he hijacked a switch box off of another year motor etc) so I figured I would fully concentrate on this next year when I go over It etc. This thing runs perfect, had it out on the water on a boat with gear, It did well.
(I can't use the current button switch as the button won't secure and will fall off under vibration.
 
A little bit of continuity is OK.

The way it works is, the ignition voltage is (sent) wired to the stop switch AND the sparkplug coils (ultimately).

The (power) is looking for the "easiest" path to ground. That very "minimal" (2 ohms) of continuity is not enough to stop the (charge) from jumping the gap on the plugs where as "total continuity" WILL funnel the power away from the plugs.

The new switch you have should be more than fine.
 
[h=3][/h]

You are both correct, I disconnected the switch, (duh, should have done that in the first place) and it had no internal continuity, so it was the connections having partial continuity from that ignition system which I will still have to learn.
And jeff horn switch is perfect. I googled horn switch and found the one that is in this franken outboard now[h=3]Seachoice 11781 PUSH BUTTON STARTER / HORN SWITCH [/h]Except the one in there is missing the mounts and self implodes as it is part broken
 
And I forgot to ask about the thermostat on these bullit-proof little portables by Mercury. Can I run this motor without the Thermo. I cooked it and see it opens at 140^ I see how it works, (there is a by-pass chamber that allows mmm restricted but decent flow through the powerhead. the water out the rooster-t is however hotter than my 1973 7.5 (110 series) I guess youns may know of some reasoning behind this. In my day I ran my built cars at 160. I had a 350 chevy omc in a correct-craft and it did not have a thermo, it ran at 130 degrees as per dash gague, while picking up the standard summer lake water temps of say 75 degrees. I put many hard hours on that boat, no thermo just the channeled new water coming from hull inlet and dispersed to motor and x-manifolds by a hughe stand alone belt impeller.

so am i gonna crack omething or do a lot of knowledgeable people do it, (no thermo on the 9.8 1979)
 
I don't recall if the 9.8's/7.5's came from factory or not with a thermostat.

In 86 when they brought out the 6/8/9.9's they left the stats out - probably saved them 50 cents a motor.

Now, without getting into an argument about possible damage that could be caused by not installing one, I can give you my observations.

I have installed stats on my pair of 9.9's and my 15 horse which came "without" - I think they go for about 20 bucks a pop with the gasket.

With one in place you get a better/smoother idle than without, particularly in colder weather/colder water - just gets up to operating temp quicker.

You could also argue that they will extend the life of (any) the motor.

However, I routinely work on these "portables", some are close to 40 years old, used regularly in some cases, only in duck season with others - most don't have "stats" and they are running better than most 4 strokes after 2 years of use.

Unless you are running the motor in a hot tub, a thermostat is well worth the few bucks that they sell for...
 
Frankly, you don't need a stop switch on that motor, and many of them I work on do not have one (for the same reason as yours). If you need to temporarily shut her down, just choke it off; and when you're done for the day, you SHOULD run the motor dry by pulling the connector off. Not good to leave ethanol fuel in a carb!

Jeff
 
Thank you gents for the info.
I will be at a lake and testing w a little fine tuning of a couple motors this weekend, weather permitting , keep fingers crossed.
also just for the interest, did you all read the one post where the marine mechanic told me he had a customer with a phase maker with the red module and he was in process of sending it back to c d i so they could repair it, actually said they were going to rebuild it. When I get back to that marina over the next few months I will ask how it is working out and if it is indeed C D I who is working on it. have you ever heard of this?
also i don't know too much about johnny rudes yet, but the couple i had run in a tank worried me cause they did not spray a rooster tail till they warmed up, they had water spattering out their exhaust, so the guy told me they were getting water, then all of a sudden the 15 hp shot out some water, on the 1979 merc the rooster tail shoots through a by pass right away so i don't have to worry.
 
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