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Compression test on 150hp merc EFI

budgie14

Regular Contributor
Hi,need advice on doing a compession check on a 1993 merc 150hp v6 efi. Do i need to disable the efi? Will winding it over with kill switch activated protect the ign coil ,and disable efi? How to achieve full throttle,is it by pushing button on gear lever to disconnect it from gear selector cable? Any advice greatly appreciated. Looking to buy this boat this weekend
 
Wow, New Zealand. Been to Australia, stayed over a month while travelling around in a tiny rented RV, great place. They drove on the wrong side of the road there, I got plenty "thumbs up", so a guess my driving was pretty good? Eh?
Do the compression test with all plugs out and just wedge open throttle valve part way to ensure good intake air. To avoid any feed into electrical system trigger a direct power to STARTER side of the solenoid when you need to crank. That way all power will be isolated to only spin the starter. It cannot get back across the solenoid into the "HOT SIDE". Configure a jumper in a way so as not to arc at the starter, or at the battery, but touching 2 cables together in your hands in order to crank. You will, therefore, get no ignition or fuel anywhere and you won't have to disconnect any wires. Of course, the key will be left in the off position.
 
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No,no...just :1) pull all the plugs, 2) pull kill tether, 3) install gauge and crank with key. Kill tether kills ignition and thats where ECU gets it signal to fire injectors. No spark no injector....Compression spec 110-135psi
 
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Guy wouldnt give me his adress,so bought another boat,with 115hp 2001 johnson,290 hrs ,v4 sounds very good. Yes,great place in NZ,sunny,cheap,good society etc,apart from some Australian visitors
 
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