Mercury 150 Ignition

[Engrave1]

I have inherited a 1978 Ranger Aztec w/ Mercury 150 ( Black Max ). After a few trips to the water and trying to figure out
what is causing this motor not running to its full potential. The motor is very slow to plane off, but once on plane seems to
run fairly well, will very rarely ever have enough power to load it all the way on the trailer when backed in at boat launch.
Here is what I have found so far; (1) the tach didn't read the right rpms so I traced it back to the rectifier and sure enough
the rectifier was shorted, so I replaced it, tach worked properly for a while then back to same. I have removed the stator
and of course it is shorted out as well, so I have now ordered a new stator ( from iboats ) and am curious now if when I
install new stator and rectifier that if by chance my switchbox and/or trigger is shorted out as well is it going to fry my new
stator? Is there a way I can bench test the trigger and switchbox before I go any father with this?
Thanks for any help here...

 

[alldodge]

I have inherited a 1978 Ranger Aztec w/ Mercury 150 ( Black Max ). After a few trips to the water and trying to figure out
what is causing this motor not running to its full potential. The motor is very slow to plane off, but once on plane seems to
run fairly well, will very rarely ever have enough power to load it all the way on the trailer when backed in at boat launch.
Here is what I have found so far; (1) the tach didn't read the right rpms so I traced it back to the rectifier and sure enough
the rectifier was shorted, so I replaced it, tach worked properly for a while then back to same. I have removed the stator
and of course it is shorted out as well, so I have now ordered a new stator ( from iboats ) and am curious now if when I
install new stator and rectifier that if by chance my switchbox and/or trigger is shorted out as well is it going to fry my new
stator? Is there a way I can bench test the trigger and switchbox before I go any father with this?
Thanks for any help here...

Howdy

I would suggest running a compression test

 

[Engrave1]

thanks AllDodge, I agree, I will get myself a compression tester. Do you know what sort of numbers should I be getting on a 78' model 150? This boat doesn't have
a lot of hours on it, It was/is my dads that he bought new, so I know all the history on this boat. I forgot to mention I am/was getting no fire on #6 and
( using a timing light ) it appears as if several of the other cylinders were firing very erratic ( not a consistent fire, short time, then fire again ). I rebuilt all of the carbs last year and was surprised at how well they all looked.

 

[alldodge]

Unable to say for sure, not that good with outboards. I would look it up but would need the motor serial number. Here is a link to where I would look, it has most all the manuals
http://boatinfo.no/lib/library.html

 

[Dukedog]

that's gonna be first generation 2.0 150.. comp with an "unknown" (even new) gauge should be consistent at tha very least... with a "known" accurate gauge should be 110 + at that age.. if you haven't already, go over every wire on tha ignition.. ie: trigger, stator (but ya say ya already replaced), all switch box wires to coils, plug wires, motor harness, all grounds and etc... check for insulation break down.. losin' fire to one or two plugs (if on same side) is usually a switch box.. best ta change "both".. on occasion, a bad one can "mask" a good one through tha bias circuit causin' someone to actually changed out tha good one.. a stator or trigger failure usually takes out tha whole bank on either side... easy way ta check coils is jus move tha lead comin' from tha switch box ta see if tha problem follows...

 

[Engrave1]

Thanks Dukedog,

no I have only replaced the stator and the rectifier for now, did that last night and haven't tried to start it up yet. The old stator was toast.
I guess what my concern is ( since I just cant afford to sink a whole bunch of money in it at one time ), if I replace the stator and my trigger
and/or switchbox is bas as well, will it cause my new stator to short out if I try to run it. do you think it might be better to leave the rectifier
unplugged for now and isolate the two wires from the stator.

 

[Dukedog]

shouldn't hurt a thing with it all hooked up but I would do a tdc and timin' thing first.. probably ok but I jus don't trust anything electrical ta be tha same as tha one comin' off and being replaced with another.. triggers are usually tha most dependable 'lectric part on that motor.. can be checked with ohm test.. (see below)... from tha computer it sounds like ya gotta switch box issue though.....

jus from memory think this is what they should be ona ohm meter... all readings are R X 100

brown and yellow ...... 1100 ta 1400
white and red............. 1100 ta 1400
purple and blue.......... 1100 ta 1400

any more or less replace it.....

 

[Engrave1]

Thanks Dukedog,

I went on ahead and took it out and ran it last Saturday and was very pleased with the way she ran wide open,
tach worked and was reading right around 5000 RPM at wide open, but still a little slow getting on plane,
and didn't want to push itself up on the trailer at boat ramp. I checked spark with a timing light and now all
cylinders are indeed firing. Know I don't know if im just expecting too much from such an old motor or if
I should keep throwing money into it until I get it to run like I remember it running years ago. Dang switchboxes
are so expensive it may be a while before I can swap those out.