Starting Issue - 1989 Supra Mariah

[asmithcveg]

So I have a new to me boat with 360 hrs on the original motor. The seller advised me of a weird startup issue with it, but played it off as normal.

Here's the issue (if it really is one): Both the main cluster switch AND the Acc switch on the dash must be activated to start. Additionally, the spark plugs don't fire unless the key is no longer turned all the way to the start position. In other words, I have to turn the key and the starter turns the motor. I then have to kinda time when I let off the key for the ignition to actually fire. I suspect some wonky wiring repair has occurred sometime in the past.

I should point out that the motor is definitely difficult to start when cold despite me being very familiar with carburetor engines.

[crystal waters]

So I have a new to me boat with 360 hrs on the original motor. The seller advised me of a weird startup issue with it, but played it off as normal.

Here's the issue (if it really is one): Both the main cluster switch AND the Acc switch on the dash must be activated to start. Additionally, the spark plugs don't fire unless the key is no longer turned all the way to the start position. In other words, I have to turn the key and the starter turns the motor. I then have to kinda time when I let off the key for the ignition to actually fire. I suspect some wonky wiring repair has occurred sometime in the past.

I should point out that the motor is definitely difficult to start when cold despite me being very familiar with carburetor engines.

Doesnt sound at all normal.
What size and make of motor?
351 ford pcm ?

[michael hunter]

Does it have points or electronic ignition? Where are you located?

[asmithcveg]

351 Ford pcm with points. Located in northwest arkansas

Edit: I should point out that someone has messed with the main wiring harness as evidenced by it being wrapped in electrical tape. Thankfully, I have the engine service manual that contains the wiring diagram. My next order of business is to take that tape off and see if all the wires are where they are supposed to be. I also have a decent amount of corrosion on the electrical contacts at the starter relay, fuse, etc. that will be cleaned away..

Another question (not related to the starter): how much should the prop spin while the boat is running on the trailer in neutral?

[crystal waters]

351 Ford pcm with points. Located in northwest arkansas

Edit: I should point out that someone has messed with the main wiring harness as evidenced by it being wrapped in electrical tape. Thankfully, I have the engine service manual that contains the wiring diagram. My next order of business is to take that tape off and see if all the wires are where they are supposed to be. I also have a decent amount of corrosion on the electrical contacts at the starter relay, fuse, etc. that will be cleaned away..

Another question (not related to the starter): how much should the prop spin while the boat is running on the trailer in neutral?

Go to this thread

https://forum.supraboats.com/showthread.php?15453-Clockwise-vs-CCW-LH-vs-RH-Standard-vs-Reverse-Help-me-get-this-down-once-amp-for-all

[asmithcveg]

Thanks for the link - some good information in there for sure.

In regards to the transmission, the PCM manual states that a blockage in the control valve may be the culprit for my excessive prop rotation in neutral. My question is, can I remove the control valve with the transmission still in the boat?

[michael hunter]

Thanks for the link - some good information in there for sure.

In regards to the transmission, the PCM manual states that a blockage in the control valve may be the culprit for my excessive prop rotation in neutral. My question is, can I remove the control valve with the transmission still in the boat?

That is called a dirty neutral. It is most likely because the clutches inside the trans are warped from excessive heat . There are a lot of transmissions with that problem . It will work for a long time as is but it will inch forward in neutral . The fix is a trans rebuild.

[asmithcveg]

It also does it in neutral reverse as well. The common component according to the Trans manual is the control valve unless both the forward and reverse clutch plates are warped. Any thoughts?

[asmithcveg]

So I was wrong in my earlier response. It actually has the petronix electronic ignition installed.

[michael hunter]

I have a PCM # RP173072 electronic ignition conversion kit new in the box . I don't know if its made by petronix. I use HEI distributors in my 351 engines single wire hook up 60,000 volts to the spark plugs.

[asmithcveg]

So Vince with skidim came in for the win (hopefully). The solution is to run a hot wire from the ignition terminal on the starter relay (should be the only empty terminal) to the hot side of the ignition coil. Will confirm later if this is the fix or not.