Mercruiser Wouldn't Stop - Then Would not Start Back Up Again ???

[kevinstan]

Hello everyone - I haven't posted in a while, but I have a question. Took the family to the lake yesterday on the new to me 1997 Bayliner with Mercruiser 3.0. Boat started fine at the ramp and ran strong for about 20 minutes of cruising. Once we stopped I turned the key off and the motor was still firing and running. Sputtering, but still running. I used the kill switch to turn it completely off. After we swam and hung out for a little while I went to start the boat back up and nothing. Motor kept turning over but no fire to start it up. I double checked the kill switch was back in the "run" position and it was. Tried so much I ran the battery out and had to call for a tow back in. Not a good July 4th, but now I need to troubleshoot and determine the problem. Not really sure where to start. I am thinking it has something to possibly do with the kill switch and I was thinking about bypassing it to test. Would I disconnect both wires from the switch and connect them together? Or just disconnect them? Any other things I could check or can someone suggest where to start? Thanks in advance for any help you guys can give.

 

[Scott Danforth]

Is your motor a TKS?

 

[alldodge]

connect them together?

Connect together and also check for 12V at the + side of the coil

 

[kevinstan]

AllDodge: I will connect the two wires from the kill switch and try today when I get home. How do I check the 12v at the + side of the coil. Not sure I know what im looking for exactly.

 

[poconojoe]

You said it was sputtering. It sounds like it was dieseling (also known as run-on) when you turned off the key. From what I recall, it's due to carbon build up on the pistons. The carbon is so hot it keeps the engine running even without a spark. Similar to how a diesel engine operates.
I could be wrong since it stopped when you pulled the kill lanyard.
Hopefully some of the geniuses here will chime in.

 

[AlabamaNewbie]

Connect together and also check for 12V at the + side of the coil

If you have 12v on the + side, pop your distributor and check your points. Make sure they are set to proper gap when open. The side of the motor should have a sticker with some engine specs and it should have the points gap. I believe it will say ".018 - .025" . I set mine to .022 and it fired right up. Make sure you have the battery disconnected when checking or setting the gap on the points. If you have power to the coil, then you have power to the points. When you open the points, it will jump a spark. Now if you live on the edge like me - you can leave the battery connected, key in run position, and open the points. If it sparks a bright blue spark, you have your voltage going through the ignition coil. If its any other color than bright blue, you have power but its weak. Obviously if there is no spark but you have power on the + side of coil, then its time for a cap, rotor, points, and condenser replacement.

 

[kevinstan]

I believe it is an electric ignition - no points. Just a cap with one single metal spring in the middle similar to the rotor button. But no points. There were 4 metal contacts around the outside area of the inside of the cap, but that was all. Nothing to check a gap on.

 

[Scott Danforth]

no points in 97.

thought dieseling, however OP stated, killing battery switch killed motor.

TKS diode going bad can lead to not shutting down.

 

[alldodge]

Would help if you could answer Scotts question in post 2

TKS carb (note the black solenoid valve on top left)

Merc carb

 

[AlabamaNewbie]

I meant to preface that with " I am not a boat motor mechanic...".

My mind immediately went to issues I've had, just wanted to help. I'll go back to my corner now and just watch.

 

[alldodge]

You need a think skin around this crowd, don't think they mean to be mean, but they are real quick on the trigger to point out miss and short comings.

 

[kevinstan]

I will have to look and double check. Not sure if its a TKS or not. I will get pictures of it shortly when I get home.

 

[AlabamaNewbie]

You need a think skin around this crowd, don't think they mean to be mean, but they are real quick on the trigger to point out miss and short comings.

Oh I don't have a thin skin at all. It takes a lot to offend me or upset me. I look at it like - yeah i was way off on this one, but someone else could be reading this and say " you know, I forgot about those points, maybe I should check mine" and that keeps them from getting stranded 5 miles out with the points finally go. You never know when a stray comment might help someone else out.

On that note - don't forget to clean and lubricate your firearms, even if you haven't used them. High temps and high humidity is more harsh than running 500 rounds through. They deserve some love too.

 

[poconojoe]

no points in 97.

thought dieseling, however OP stated, killing battery switch killed motor.

TKS diode going bad can lead to not shutting down.

Yeah, was thinking the same thing about the kill switch, but figured I'd throw the dieseling idea out there anyway.

 

[scoflaw]

Gun safe with a golden rod heater...never have to clean or wipe down an unused firearm again. Just a tip.

 

[garbageguy]

Maybe the engine finally shutting down being concurrent with "using the kill switch to completely turn it off" was coincidence?
Didn't see that discussed as a possibility - but that would likely complicate troubleshooting. To me, dieseling and kill switch malfunction are likely separate issues.

 

[porscheguy]

Maybe the engine finally shutting down being concurrent with "using the kill switch to completely turn it off" was coincidence?
Didn't see that discussed as a possibility - but that would likely complicate troubleshooting. To me, dieseling and kill switch malfunction are likely separate issues.

I agree. In my experience, dieseling tends to last about 2-3 seconds at most. And it’s quite possible the dieseling stopped at the precise point the kill switch was pulled.

TKS came out in ‘03 or ‘04. Unless his boat was repowered, it won’t be TKS.

I’d pursue fueling issues as the culprit due to the dieseling at the last shut down.

 

[harringtondav]

My 4.3 LX w/Weber 4 bbl used to diesel on. Until I found the sweet spot in the idle mixture screws. It was a little too rich. That may explain the sputtering, but not the hard starting. Unless the mixture is way too rich, or floats too high - flooding. Also I found out the hard don't use ethanol. It will boil in a hot engine compartment. This causes starting and power problems until fresh, cool gas is supplied.

 

[poconojoe]

So, what exactly is TKS? My (2003) 4.3 states MCM on the spark arrestor. And what does MCM stand for?

 

[alldodge]

TKS - Turn Key Start
MCM - MerCruiser Marine (sterndrive)

MIE - Mercruiser Inboard Engine