'84 mercury150 loss of power after idle

[redneckboater]

I just aquired a '84 mercury 150hp outboard... It runs and idles perfectly on the trailer. When I put it in the lake it runs fine at idle speed but if i add any throttle it just loads up and boggs and never catches up. I installed new fuel lines and plugs hoping to correct the problem. This had no effect. Any suggestions would be greatly appreciated.

 

[honestcharlie56]

Re: '84 mercury150 loss of power after idle

i would have the spark checked, try to find an actual tool for this, its like a little deal that has 4 prongs on a box that shows spark and plugs into the plug wires, i think you have two ignition boxes if memory serves, and if the spark cant discharge you WILL damage the ignition boxes. i hope this helps, also check compression check to make sure that the timing advance is operating, really hope all this helps

 

[redneckboater]

Re: '84 mercury150 loss of power after idle

Thanks for the reply. The compression is good on all cylinders. I'm gonna try getting a sevice manual at my local shop this week for it. So today im gonna see how my spark looks. Thanks again

 

[j_martin]

Re: '84 mercury150 loss of power after idle

I've seen folks change carbs on them without knowing that about a gazillion things change even though the carbs look alike. When they bog out, they try to tune it for awhile, then give up and sell it.

Just a thought.
John

 

[redneckboater]

Re: '84 mercury150 loss of power after idle

Alright, I think I have found the problem... I checked my spark on all six cylinders and im only getting spark on the right half of the engine. Im thinkin its one of the two switch boxes. One of them feeds spark to one side then the other feeds the other side. Is there a way to "check" these boxes? If so any help would be greatly appreciated.

 

[honestcharlie56]

Re: '84 mercury150 loss of power after idle

yes sir, simply switch the boxes and if the spark on the cylinders switches to the other side with the box change that means that the box not providing fire is dead, replace it and hit the water man.

 

[redneckboater]

Re: '84 mercury150 loss of power after idle

Thanks honestcharlie... That makes perfect sense for a way to check the boxes. what is the bast way in replacing one? Should I buy new or used? Ive also heard u cannot just replace "one", that u must replace them as a set or u will burn the weaker one up? Then finaly, what causes these to burn up? do they just go bad or is it a result of another weaklink in the electrical system? Thanks guys your help is greatly appreciated!

 

[redneckboater]

Re: '84 mercury150 loss of power after idle

I'm still having problems