1996 Mercury 150 EFI *cold compression & leak down test *

[CWKemp]

Looking at a 1996 Ranger. An older model that I’ve always liked, so I really want this boat/motor to check out good. The boat is 11 hours from me, so I asked the owner to have a compression and leak down test done and send me the results. Owner dropped the boat off with mechanic this morning. For some unknown reason, they did both tests without warming the engine up. Cylinders 1 - 5 came back at 120 and #6 at 115. Leak down test looked like this:
#1 - 17% leakdown
#2 - 15%
#3 - 15%
#4 - 32%
#5 - 20%
#6 - 4%

Is this any useful info considering the engine was cold and has not been ran since November? Owner keeps it in a heated garage, and said the boat runs wonderful. Serial number on this engine is 0G361524.

[lpugh]

I would suspect testing errors. If not ran and warmed up first the test are meaningless, esp leakdown

[CWKemp]

I would suspect testing errors. If not ran and warmed up first the test are meaningless, esp leakdown

Yes Mr Pugh, “Meaningless” exactly how I feel about the test as well.

[lpugh]

If on a cold motor compression and leakdown were within limits, all is good, however this is not likely. When a motor is cold and may have not been run for quite sometime several things happen that would make a failed test invalid
1. Pistion ring gaps are much larger due to the low temps allowing compression to blow by the rings
2. May have lost a great deal of the oil film that greatly helps ring seal
3. When motors have not been ran for while the carbon deposit that are in the rings grooves will absorb moisture causing it to actually grow larger (bulging a little you might say) This can absoluty destroy ring sealing
4. Due to the above you will usually have a much lower cranking RPM which will reduce compression reading

I would pesonaly recomend a decarbon treatment like power tune, run the motor untill temps are all the way to thermosat controlled temps and repeat the test
Be sure you have the correct battery and that it fully charged and consider leaving the charger on the battery while compression testing
Throttle held wide open and coils primary disconnected or engine kill activated, no sparks from secondary please

[Merc2.4]

While this is all gud info , my guess is yes I'm sure it prob runs , but if the same test were done while warm the #s will b worse , especially compression, prob lose another 5 -10 lbs. 32% leak down ,most requires a rebuild by then. For the boat to b 11 hrs away , u would have to get it for a hell of a steal impo. Unless u can get a repeat test while warm after a decarb, best of luck. I know getting that kind of news sucks when ur looking forward to the purchase

[CWKemp]

Thanks for the info guys, Im certainly not driving 11 hours north base on those numbers. Im no outboard mechanic, but Ive worked on enough older boats to know that a leak down test should be done after the motor has been warmed up.

[blackboat]

I guess it all depends how bad you want the boat.If it's clean and runs good,the guy's going to sell it no matter what the test results are. Realistically,a lot of buyers won't even ask about them. You might have to take a road trip and roll the dice.Those tests will be better when done correctly.Take your equipment and do them yourself. Snooze you lose,lol

[EuropeanAM]

Compression tests and leakdown tests MUST be done with the engine at OPERATING TEMPERATURE.

Hence those tests are meaningless. It's also very likely that the "methods" used to obtain the leakdown were not correct or consistent (all but one cylinder's percentage says "Run FOrrest, Run"!

[CWKemp]

Thank you for all your responses

[Merc2.4]

Pretty weird that the lowest compression cyl has the best leakdown #s. I'd want another test by a diffrent mechanic

[JOE54]

^^^^ +1 thought the same

[CWKemp]

^^^^^^^Yes. Spoke to the owner last night. He knew the motor should have been brought to operating temps before both tests were done. He took one look at the printout and knew something was wrong. So he ask the mechanic if he had warm the motor up first. Mechanic said, "no, those are cold numbers. Leak down tests arent important on 2 strokes anyway. Only 4 strokes." I believe my seller and the mechanic had a disagreement at that point, I didnt get all the details on that though. Long story short, seller is now taking the boat to a different mechanic. I spoke the seller a number of times, he has sent me videos of every inch of this boat. He knows Im 11 hours away and wants to get as close to an idea about the health of the motor as he can before we make an agreement and drive up. Only problem right now is that,the new mechanic is about an hour away. He is hoping to get it to him in couple days. Thank you all again for your input and advice

[Merc2.4]

Well least ur seller is willing to travel the extra distance to try and make buyer happy , and taking a risk of not selling it afterward, hopefully the #s come back alot better. best of luck

[JaySmithRacing]

If the leakdown test is done by a competent tec those numbers are horrible, my leakdown numbers that will give me the go ahead to rebuild is 10% or more

JMO Jay @ JSRE