1985 200 HP Mercury Black Max - wont plain

[greggnat]

Hi everybody,
I'm new at this and I'm looking into buying a 1985 Ultra Glide boat for me and my family. The boat is in good condition and price is right. The complaint is that it won't plain out, 20 - 25 mph only. I'm mechanically inclined and can work on engines. I took a compression test this morning and looking at the engine from the back, left bank top to bottom I have 100, 105,125 psi. The right bank top to bottom 125, 110, 120 psi. The owner said that the spark boxes needed to be replace? Is the compression variation enough to create the problem or is there some suggestions to look into before I make a commitment? Any suggestions or comments would greatly be appreciated.

 

[Barnacle_Bill]

Re: 1985 200 HP Mercury Black Max - wont plain

Those compression reading are NOT good. Bad switch boxes can certainly keep the motor from running properly.

 

[greggnat]

Re: 1985 200 HP Mercury Black Max - wont plain

But are the compression readings like they are bad enough to stop the engine and boat from plaining?

 

[Barnacle_Bill]

Re: 1985 200 HP Mercury Black Max - wont plain

It should still get up on plane with those readings but not with bad switch boxes.

 

[greggnat]

Re: 1985 200 HP Mercury Black Max - wont plain

Sorry for the possible miss info on the boat and mph, it was brought to my attention that the correct mph and not being able to plane was only top speed of 15 mph. I still belief, that with those compression's on the engine, the boat will not plane besides of possible other problems. I know that there are are many other possible problems but any other input would be greatly appreciated. Thanks for your time.

 

[achris]

Re: 1985 200 HP Mercury Black Max - wont plain

Do a spark check... If you have lost spark on the odd or even bank, then a switchbox or stator has failed... If you have lost spark on an opposite pair, then the trigger has failed.

Chris........

 

[greggnat]

Re: 1985 200 HP Mercury Black Max - wont plain

Changed out the switch box, one cylinder not firig. Compression came up to 150-125 the lowest. Gets up and planes great. Rebuilt the water pump and cleaned out the carbs, took it out for a run. Ran good for a bit and then starting running rough and wanting to die. Thought maybe sucking air. Changed the primer bulb and fuel line and connections, run for a bit and at 2800 rpm the alarm will sound constant and tach needle acts crazy. Any suggestions? What are the alarm codes for this particular engine to try to fix the problem. Any help would be appreciated.