what can I sell my engine for?

[sti1471]

I have a 1981 Mercury canadian 80 HP outboard engine, with the tunderbolt ignition. It runs, and seems to be in great condition. My mechanic looked at it and said the cylinders are showing 125PSI, and he timed and adjusted the carbs about 35 days ago.

A guy is looking at buying it, and he took it to his mechanic for a pre-buy inspection. His mechanic said that everything looks good except Cylinders #1,2,3 have 95PSI and #4 shows 85PSI.

I am not sure where the difference between mechanics comes in at between the two mechanics, but since the PSI came back how it did, he is offering $475.00 for the engine/throttle lever when it was originally going to be 850.00 if it registered at 125psi.

Is $475.00 what I can expect to get from this engine, or should I pass on this offer?

Thanks everyone

 

[GT1000000]

Re: what can I sell my engine for?

Hi sti1471,
I don't know all that much about boats, but I am a certified ASE automotive technician.
Here is what I can tell you about compression ratio testing.
A- Is the engine hot or cold?
B- is fuel getting into the cylinders while testing?
C- what are the mechanics using to spin the engine, a rope or the starter?
D-is oil being squirted into the cylinders before checking the readings?
E- How fast and how many revolutions are they spinning the engine before taking a reading?
F- Are all of the plugs removed from the engine before testing or are they taking them out one at a time?
The point is, both mechanics need to do the test the exact same way to consider the results equal.
If just one of the testing procedures vary, so will the readings.
Also, remember that when it comes to compression testing, the 10% rule applies. If, any cylinder reads less than 10% of any of the other cylinders, that could indicate a problem.
As an example, if 5 out 6 cylinders read in the 100-110 pounds per square inch of pressure and the number 6 reads 88psi, it is more than the allowable 11psi of difference between the other cylinders. Hope this helps.
Before making a possibly costly mistake by either party, I would verify the test results. And, I would point out that, even though the readings the second mechanic came up with seem a bit low, the 10% rule is only off by a POINT 5psi, that is half of a pound per square inch of pressure.
Best of luck and Float, Float On
GT

 

[sti1471]

Re: what can I sell my engine for?

Those are good points. However I am not sure how the tests were done, I just dropped the boat off and left. The buyer of the engine says that the mechanic is worried that the #4 cylinder is the lowest when normally it is #1 (top). He says he is only willing to go 475.00 because he is being told the compression of showing signs of possible future issues.

I am just curious as to if an 1981 80 HP engine with 125PSI compression will get much more than 475.00. If it is only a 100.00 difference then I would just sell it to him, if it is a 300.00 difference then will decline his offer.

Thanks guys.

 

[zopperman]

Re: what can I sell my engine for?

a compression test can be variable. your cyls are fine. if you warm up the engine and put some oil on the plugs, do the comp test in front of him and it will read fine. My cyls read 70 across all three and then 110 the next day. its more important taht they are close together. You should see 700 for that engine...

 

[62 ROYAL SCOTT]

Re: what can I sell my engine for?

HEY,GOOD INFO.GT1000000000000. [ sti1471 ] I would take it back to the tech that you took it too. With the guy that wants to BUY it That WAY YOU BOTH CAN SEE TO CHECK IT OUT.THEN YOU BOTH CAN DECSIDE.--------SELL OR BUY------PLUS IF IT 125 PSI. IT'S $850 AND THEN YOU KNOW WHERE YOU STAND.

 

[nwcove]

Re: what can I sell my engine for?

you can sell it for what someone will pay.....not a $ more.

 

[V153]

Re: what can I sell my engine for?

If it were me I think I'd take the $475 and run. 30yr old motors don't fetch much more than that. Does it have tilt & trim?

To give you an example I was happy to get $350 for a '81 65hp Merc a few weeks ago. And it was a clean, good running freshwater motor with controls. Doesn't seem like very much does it? Sad to say they don't appear to be worth what you or I might think. 'Specially in this crappy economy.

 

[woodsyfeller]

Re: what can I sell my engine for?

Sounds like the guy is low balling you,if your not hurting for the money Id pass and wait for the next buyer.

 

[Chris1956]

Re: what can I sell my engine for?

I would take the $475 and not look back. Of course that motor will have possible future issues, it is a older motor, and stuff doesn't last forever.

 

[5150abf]

Re: what can I sell my engine for?

A compession tester costs $20, get one and test in front of the guy with the engine warm then there is nothing to argue about, they numbers are what they are and as stated it isn't the number so much as that they are within the 10%.

He is trying to low ball you, shoot the middle maybe and take $600 or let him walk.

 

[crackedglass]

Re: what can I sell my engine for?

A compession tester costs $20, get one and test in front of the guy with the engine warm then there is nothing to argue about, they numbers are what they are and as stated it isn't the number so much as that they are within the 10%.

He is trying to low ball you, shoot the middle maybe and take $600 or let him walk.

I agree with this suggestion.

A mechanic can fudge a compression test in either direction and every gauge can read differently.
A proper compression test is done with the engine warm, well lubed, and with the throttle plates wide open.
Its also normal to crank an engine long enough to obtain the peak compression on each cylinder, this should take about an equal number of cranks per cylinder.
My bet is if you went to see this mechanic, paid or friendly with the buyer, he'll most likely crank the engine only long enough to gain a minimal reading.

With that said, I own a 1982 80hp US motor, it's well used, it came to me on a junk boat but runs great and has 145 psi give or take a few psi on each cylinder. This is a saltwater run motor that's been through many owners. When I hear a Mercury has only 125psi, I have to either wonder about the compression test or the condition of the motor.
If that motor has only 85/95 psi of compression remaining, it would no doubt be lacking in performance, it may run smoothly but will no doubt be down on power and maybe even hard to start.

Now on a good running used motor, regardless of year, with new or near new compression I'd expect to pay in the 1,000 to $1500 range for a motor needing nothing. If it's a bit tired and 'just a running motor' so to speak, then $500 or $600 is about all it will bring. You could sell running motors in any shape all day around here for $475.
I'd tell them $700, see if he counter offers in the middle and let it go, if your confident that the 125psi readings your guy got were right. If those readings too are off, you will be selling yourself short on a good motor.

Don't get me wrong, I like to get a deal any time I can, but usually those deals don't include going nuts checking compression and seeing it run. I'll often buy perfectly good motors from people who have no idea what to do with an outboard for $50 to $100, many, if not most are just fine needing nothing more than basic maintenance and a water pump impeller.

 

[Sea Rider]

Re: what can I sell my engine for?

For the experts : Is it wise to consume all carb bowl gas before making compression test, as probably will have some fuel being taken to the tester when engine is cranked ? Assume there are readings differences testing hot and cold engines, right ?

Happy Boating

 

[ward cleaver]

Re: what can I sell my engine for?

I sold a 1961 40hp Johnson for $600. Thats the market in the Seattle area anyway.

I would expect to get at least $700 for yours. If I were trying to buy yours I would offer around $450 to see what you would do. If you advertise $700 you should plan on selling at around $600. Shouldnt have to come down more than that. I would ask around $900 in my market. You can judge how reasonable your price is by the number of folks that respond to your ad.

BTW you can borrow a compression gauge at a NAPA store for 48 hours for free.

 

[DonNZ]

Re: what can I sell my engine for?

Something not mentioned sofar is battery condition as this will affect the cranking speed. So have a fully charged battery and retest first cylinder again after last to confirm. I wouldn't put oil in the cylinder as this will bring the reading artificially up and is used to test rings condition.
I usually crank for a good half doz cycles or until the compression gauge stops rising at wot with ignition leads grounded ( NEVER run a ignition system with spark plug leads floating in free air)
Regards Don