1999 Mercury 90hp Compression????

[bassfisherman8]

Hey guys,

I am going to look at a 1999 pro team 185 bass tracker with a Tracker Mercury 90HP 2 stroke outboard. Wondering if any of you guys know what good compression would be for this engine because I am new to boats and dont want to make the mistake of buying a bad engine. Any info on the engine would be greatly appreciated!!!!!

Thanks,
Stephen

 

[M9.9]

Re: 1999 Mercury 90hp Compression????

Suggest you look-up the compression rates on the net. But can say I do four types of compression tests before buying a used outboard on each cylinder: Cold Drytest(engine cold), Cold Wet-test, warm (engine warmed a couple of min) and hot (engine warmed 5-10 min). For me, any Cylinder reading under 100 lbs Fails and nothing more than 10 lbs varience from the highest/lowest compression reading of all other cylinders in each of the three temp type tests.

There are no-doubt people here who can answer you better than about this. But for a start I would consider the above. Good luck.

 

[sutor623]

Re: 1999 Mercury 90hp Compression????

Stephen, there are other factors that should be considered, although compression is definitely the biggest in my opinion. Run the compression tests as m9 has said, and if you can pull the bottom drain plug in the lower unit. See if there are a bunch of metal shavings on the magnet, then if the seller allows you (and he will if he wants to sell the boat) put a small oil pan under the drain hole and unscrew the upper drain plug, just enough so that you can see the color of the oil. If the oil is milky then there is a chance that you have a lower unit leak. No biggie, but will require some work. Just make sure there are no big metal chunks in the oil. Make sure that the motor is "peeing" out of the tell-tale hole, and try shifting gears to make sure that they all work. Check the steering, and the choke levers as well. If all of these check out, then you have yourself a good motor. And one last thing, make sure the motor idles well. "Hopefully you know what to check when checking out the boat." Good luck!!

 

[Silvertip]

Re: 1999 Mercury 90hp Compression????

There are no choke levers. This engine has an enrichment solenoid. In my view if you cannot get an on water test because the owner refuses, then either walk away or price the boat accordingly (which means lower the price to account for anticipated repairs -- expensive repairs). An owner motivated to sell a good running boat will not hesitate to show it off.

 

[bassfisherman8]

Re: 1999 Mercury 90hp Compression????

There are no choke levers. This engine has an enrichment solenoid. In my view if you cannot get an on water test because the owner refuses, then either walk away or price the boat accordingly (which means lower the price to account for anticipated repairs -- expensive repairs). An owner motivated to sell a good running boat will not hesitate to show it off.

The owner did say he was fine with taking the boat on the water. Is there anything else I should be aware of to know if it a good engine or not?

Thanks
Stephen

 

[sutor623]

Re: 1999 Mercury 90hp Compression????

Not if you dont have experience. If everything works I think you are good to go. Id either change the thermostat and waterpump myself, along with a lower unit gear oil change, or have a mechanic do it. It can save you from blowing something. (I never trust anyone when they say, "oh yeah I changed it this past spring".)

 

[Texasmark]

Re: 1999 Mercury 90hp Compression????

Cranking compression with all plugs out but still connected to the plug wires, and terminated in a spark test box or something to ground the threaded part to the engine block to prevent electrical overloading....per the Merc service manual for that engine is: All within 10% of each other and a ball park general value is 120 or above it so states. It goes on to say say that anything below 120 one could have problems....my current '02 90 triple runs right at 115 for all three and it runs fine.

Ref: Manual Merc P/N 90-830234R3 dated Dec, '97 for engines USA S/N 0D283222 and above 90 thru 125 hp.

Mark

 

[CharlieB]

Re: 1999 Mercury 90hp Compression????

The quality of the compression tester can have a lot to do with reliable #'s, some gauges read lower than the actual compression so do not be alarmed it an off brand gauge reads 100 instead of 115 or 120. As long as all cyl's give a consistent # it may be fine.

If the motor starts, idles well, and can reach the recommended WOT RPM then chances are the cyl's are in good shape.