compression

[bigdaddy08302]

Im going to chec out a new (85) merc 115 and I undertand it is s good idea to check the compression. I have borrowed the gauge to test it but I have a qusestion...do I need to actually start the motor or just turn it over to check compression? I only ask because the motor is not on a stand at hthe sellers garage..on a pallet. Anything else to check before i buy?

 

[hos]

Re: compression

to make it easier on everything pull all the plugs and then do the check. the actuall compression isn't the main thing just make sure all cylinders are withen 10-15 psi of each other otherwise you are gonna have problems im not 100% but I think it should be between 85-115 psi but i could be wrong. also make sure it is lubed up, I spray a little wd40 in the sparkplug hole in each cylinder before i start.

 

[Sunfish12]

Re: compression

Don't run the engine for a compression test.

 

[hos]

Re: compression

also see how long it has been on the pallet if its been a few years it will need an impeller and the carbs pulled and cleaned. other than that with the spark plugs pulled you can put it in gear and spin the prop by hand and feal for binding.

 

[1nebel0]

Re: compression

I always bring my spark testors with me, a battery, remote starter switch since the motor is on the ground. If i got good spark, good compression and the lower goes into gear my chances of buying a bad motor are less. I did buy a 75h.p. that tested good to all of the above however the owner neglected to tell me that it had a rod knocking once I got it on a stand...Buyer Beware.....live and learn

 

[bigdaddy08302]

Re: compression

the owner says it has been in the water last season and ran fine. I did get one more bit of info..he says it has no tilt/trim...i thought this model had that on it...if it is there but not working is that a reason to keep looking for a better motor? The thing is this..the price is very good and I cant really afford much more so I am not sure if I am talking myself into it or not.