what is a good compression for a stock 1991 2.5 merc 200hp

[camaro7081]

what is a good compresion for a stock 1991 2.5 mercury 200 hp ??????

[Fast Fred]

120lbs psi

[T-REX]

Datz what mine wuz, 120!!!

[qmaster023]

with stock heads i have seen as high as 135. however most of them are in the 120 to 130 range. right around 125 is right on.

[camaro7081]

thats what i thought (120- 130) stock wasnt sure because i have 2 -2.0 liters and 1 -2.4 liter and now im looking for a 2.5... the motor im looking at is 100 to 105 comp so i think i will pass on it for 3k(it has cle 4 hole and latum steering and cylinder on motor no helm. if i can get it for 2k ,mabee 2.5k . do you think new rings will bring up the compression ???????? or do i need pistons and a bore ???????????

[rhickox]

You would really need to mic. the cylinders to know for sure.

[stealthperf]

You should also check it with a different gauge. I have seen big differences from one gauge to another. If the cylinders are all the same compression it could be just the gauge. Usually if rings fail it will happen on one or two cylinders first. All the cylinders usually don't fail all at the same time. This is just another opinion, like rhickox said, the only way to be 100% sure is to pull a head and inspect.

[camaro7081]

yes i am bringing my compression gauge tommorow to check the compression . i dont trust anyones tools . and i know my gauge is good i checked a few engine with mine . if this engine is under 110 i will pass

[camaro7081]

i was right his gauge started at 15 psi and when spun the motor it read 115 120 . i brought my gauge and i got 105 109 psi . i will pass on motor they said that was good . i guess it is good if your going fishing . but it sounds like it has a lot of hours on it and needs at least rings . probably a full pistons and bore and all new bearings . lot of work and money . so i am still looking for a 2.5 liter anyone in long island ny ????????