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Posts: 5
Reply with quote  #1 
Hi All.

My etec tach started giving problems while on the water.

As soon as I throttle up above 1500rpm the tach needle drops to idle and it does a system check. Motor runs perfectly and revs not dropping.
When I throttle to neutral it does system check again and tach works. Until I throttle above 1500 rpm and same thing.

When I connect to the emm with evdiag, it strughles to connect. Connected twice and many times it did not.
When it connected it had no faults active or in history.
Then i tested the tach, the needle swung to 2400rpm and the program froze and disconnected

I swopped the tach and same thing happens.

I cleaned all the connectors

What can I check?

Posts: 993
Reply with quote  #2 
If you are referring to a SystenCheck tach and you mean the 4 lights go through the on & sequential off one at a time, then power to the tach is being interrupted. Check for an intermittent connection in the + and - power leads to the tach which are affected by vibrations in the boat at the above 1500 RPM point

Posts: 2,495
Reply with quote  #3 
Your tach power and EMM power for key on engine off diagnostics is supplied by the purple wire coming from the ignition switch. The engine does not require "key on" power to run so losing that connection while running would not affect the engine. If you have an ignition switch mounted in the control box then lever or cable movement could be moving the wire.

Posts: 5
Reply with quote  #4 
Thanks for the replys, it seems the system check tach tests itself and not the motor - makes sense that the tach loses power momentarily then checks itself ( yes the 4 lights)

I suspect the battery is bad. When i switched from single to dual batteries the problem disapeared. No system check when I throttle and emm connects.
But i tested this on the trailer, weather does not allow testing on the water now.

If the problems persists then I need to go through the wiring. Quite a big job...

At least the motor is fine

Posts: 213
Reply with quote  #5 
I would not be reving to 1500 RPMS on the hose. Reving an engine out of the water with no load is not good for the internals. I would limit unloaded RPMS on the trailer to less than 1000 rpms and during winterization only.
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