What is the purpose of the shunt (for timing measurement)?

[happycamper]

I need to check the timing on my VP 3.0GS, and probably advance it for my altitude. I have the OEM manuals, and I've read them, but it's not clear to me what the shunt actually does.

Another question, assuming I don't have the shunt, what would the timing be, roughly? Advanced or retarded?

Last question, knowing that the timing probably needs to be advanced, is it safe to just rotate the distributor in small increments and test run the boat on the lake after each tweak?

 

[bruceb58]

Re: What is the purpose of the shunt (for timing measurement)?

The shunt puts the timing in base timing mode. It is impossible to adjust the timing without the shunt since the electronics will be constantly adjusting the timing while you are trying to adjust it.

Don't adjust my "ear". Do it properly with the shunt. They are pretty inexpensive.

 

[tommays]

Re: What is the purpose of the shunt (for timing measurement)?

The shunt locks out the timeing advance so you can set it with out it jumping around


You can not advance it get back power lost from high altitude.



Tommays

 

[bomar76]

Re: What is the purpose of the shunt (for timing measurement)?

Last question, knowing that the timing probably needs to be advanced, is it safe to just rotate the distributor in small increments and test run the boat on the lake after each tweak?

Sure.
Just blindly twist the distributor and advance untill detonation melts a piston or two, then back off 1/8th turn.

 

[happycamper]

Re: What is the purpose of the shunt (for timing measurement)?

Thanks for the replies.

I called around and I can't get a shunt right away since I live 75 minutes from the nearest VP dealer. It sounds like a simple electrical shorting device.

I searched this forum and found the following response regarding and OMC 3.0 (I have a VP 3.0, so maybe a little different).

"You don't need a "shunt adapter".jumper the 2 white wires(both female conn.) coming out of the dist. to put it into base timing mode.Disconnect the interupt sw. and set the timing to specs."

If anyone has a picture of the shunt, or a link to a website that sells it, please reply.

 

[Don S]

Re: What is the purpose of the shunt (for timing measurement)?

Those directions are for a Mercruiser. Your Volvo doesn't have those 2 white wires, plus those instructions are missing the part about putting power to the module from a 3rd wire that is already in Mercs wiring harness.