1993 Johnson 150

[Dick Bacon]

I am going to look at a used boat this weekend. It has a 1993 Johnson 150. What would be the procedure for performing a compression test and what should the readings be ? Anything else I should look for ?

 

[Chris1956]

To perform the compression test, first remove all the 6 spark plugs. Using a piece of wire, jumper the starter solenoid (ignition off) so the motor cranks, with the compression gauge stuck into the topmost spark plug hole. Write down the results for that cylinder (should be #1 cylinder). Repeat with cylinder on opposite side, as that should be #2 cylinder. Continue to collect and write down compression numbers, for the other 4 cylinders.

Compression should be 90PSI at least, but most importantly, all cylinders should be within 15% of each other. Remember, compression gauges are often not accurate, but that are usually reliable.

 

[Faztbullet]

Inspect #1 plug to see if a tad different color as these blocks are know to be leakers. If possible test run the motor under a load and if it knocks/misses around midrange its a leaker.This will NOT show on a compression test....

 

[Dick Bacon]

Well the guy got pretty pissy and insulted that I asked for an on the water test drive and compression test. He said he would rather keep it than deal with me or the other people calling him about it.

 

[boobie]

Makes you wonder what was wrong with it.

 

[crazy charlie]

Then he keeps it and you move on to getting a good motor that checks out from someone else.I would NEVER buy an outboard without doing a compression test.Pretty much everything else can be repaired,tuned,replaced etc.,but the powerhead must check out.The only time a seller gets insulted/pissed is if the price is a giveaway or if he is hiding an issue. Charlie