4.3 TKS problem

[smallheadz]

Ok I have read every post I can find and I still have a problem with this 4.3 TKS system. So I am helping a friend and this is his boat, around 2006 Bayliner. Problem first started, hard to start when warm (he never told me this until recently) Bad diode no big deal however didn't fix it.
Second problem showed up this year , boat would blow the 15a ignition fuse in the fuse box and the boat would be dead in the water until replaced. Sometimes it would last 2 days sometimes 5 min before it would blow again. The 20a TKS fuse back at the 50a circuit breaker has never blown.

So it appears to me there is a short to ground somewhere but I have traced wires for hours.

We have a new TKS module, diode, temp sensor.( diode and module tested bad) Installed all 3 and instantly smoked the diode when started.

So after more reading I believe the TKS module gets its 12v source from the oil pressure switch and it has a constant ground. Is this correct?

I have a power probe circuit tester/wire short tester and it's showing the purple wire short to ground . I don't have the manual or diagram for this system so I am a little in the dark. I have moved the alternator harness to get it off of the manifold too. I have checked the coil and everything from front to back, but I am clearly missing something. Does anyone have any ideas? I know there have been tons of issues with the TKS and I have the service bulletin from merc. I ordered more diodes for testing and hope to have the boat in my shop where I have access to more tools and I don't have to keep running back and fourth.
Thanks for any help

 

[alldodge]

This is a block diagram for the V6 and V8 motors
TKS gets 12V from 2 sources, check the Temp switch

 

[Fun Times]

Try a 20 amp fuse in place of the 15 amp as the ignition system is normally protected by a 20.

Mercruiser 4.3 TKS -- Blown Ignition Fuse and Shorted TKS Diode

I have a 2008 Sea Ray Sport 205 with a Mercruiser 4.3L TKS engine. Recently the ignition fuse blew and I discovered that the TKS diode was shorted. After I removed the diode and replaced the fuse, the engine started and appeared to run fine. I ordered a new diode thinking that this would resolve...

forums.iboats.com

4.3L Mercruiser loud sucking noise-gctid817842 - BAYLINER OWNERS CLUB

On my 2007 Bayliner with a 4.3 Mercruiser there is a loud sucking noise coming from throttle body or carb whatever it is. See picture for where arrow points.

www.baylinerownersclub.org

https://www.justanswer.com/boat/biq0v-test-tks-module-won-t-idle-when-hot-smells.html?r=impact%7C2003851%7CBlogger.com%20Tech%20Support%20-%20Text%20Link%7C&clickid=z3uVWDXLoxyIUWPy4FS%3AWXYSUkDWa2SMKRieXM0&aff_sub_id=EdgeBingFlow&aff_sub_id2=oc5A05L8E%2FcFrofF6SHThPTQCERYtosjsWESdn5%2F59y%2F5mYJkpnT2DJw2C2nxnwf&aff_sub_id3=&aff_sub_id4=&chat_text=&irgwc=1

 

[smallheadz]

alldodge, thanks for the diagram, I put a new OEM temp switch in, new TKS module and a new diode.

Funtimes, even with the 15a in place today it smoked the diode but the fuse did not blow. Waiting on new diodes to arrive for more testing. 15a is what the boat came with new, I'm not opposed to running a 20a but I need to keep the diode from blowing first I would guess. I thought the temp sensor or the TKS module would cure it but just smoked the diode again. I need to do an amperage test once the boat gets here. Thanks for the reply I am open to any options .

 

[alldodge]

With it smoking the diode there is a short in the harness. Disconnect the Battery and plugs going to/from the components. So you can use a ohm meter to check for shorts to ground

 

[smallheadz]

yes I agree there is a short to ground somewhere, I have traced just about every wire in this boat. I will do some more testing when it gets here.

 

[QBhoy]

Hi. First place I’d be looking, would be pulling the plugs and checking that there is no water ingress from the manifolds or risers. Turn it over with plugs out after it’s been ran and in a condition exactly as it is when you find it’s hard to start and blowing fuses. See what happens and watch for any sign of water coming out the plug holes