Compression test on Yamaha LF225's

[Infinity128]

Can someone tell me if these numbers are OK for a compression test? I'm buying a GW282 Sailfish with twin 2005 Yamaha LF225TXRD 500hrs
Marina says it is all in spec but I thought the numbers needed to be between 170 and 190. I just walked away from a boat because the compression test were all in the 170's except for 3 cylinders (110 - 130). That Marina told me anything in the 130's or below would need to have the engine's replaced.

Is it more important that the numbers be within 10% or should the PSI be higher. This boat has been sitting, winterized, since last year and was run for the first time a week before the compression test.
Dry dock, no idea if WOT. Marina says the engine looks good and is within spec. they recommend service on one cylinder but said the PSI reading was fine.


PORT
1 - 138
2 - 148
3 - 138
4 - 148
5 - 135
6 - 145

STBD
1 - 138*
2 - 155
3 - 138
4 - 155
5 - 138
6 - 155

*TAN/BROWN BURN (RECOMMEND INJ.SERVICE)

 

[seasick]

The difference is more important than the actual numbers. That said if all were low, that's an issue. I don't know the actual spec for that motor but I am sure someone has the service manual.
A leak down test would help you decide
Is the marina brokering the sale and , was the mechanic from the marina?

The interesting thing is that on both motors, the readings were the same or almost the same for all 3 cylinders in the same bank. cyls 1,3,5 and 2,4,6!

Note that that model year had a lot tof the exhaust corrosion problems. If you are looking at F225s or F250s, before 2008 or there about, you need to ask if the exhausts were serviced( and the seller has proof of the service)and if not they should be scoped

 

[Infinity128]

Seasick,
Thank you for the reply. The exhausts were done about 5 years ago and they provided all the paperwork. I didn't have them checked.

I just purchased an online version of the service manual and all it says is

"Minimum compression pressure
(reference data):
880 kPa (8.8 kgf/cm2, 125 psi)

5. If the compression pressure is below
specification and the compression pressure
for each cylinder is unbalanced, add
a small amount of engine oil to the cylinder,
and then check the pressure again..."

That tells me that they are within spec.

I think the broker and marina are separate companies but the same in that they share dock/lot/parking...
Current owner is meticulous with upkeep and service. I did notice the similar readings for the same banks but I have no idea what that means (if anything)

 

[seasick]

So the motor seems OK?

 

[Infinity128]

Unfortunately the service department isn't helping much other than saying "I ran the test and they are within spec". I guess what I want to know is are they "Good - Good" or "Good - but on their way out" if that makes sense. I'm completely clueless on this (but trying to learn).

 

[Infinity128]

Yes, the motor ran well in the sea trial. We didn't notice any issues.

 

[Halfhitch]

As far as the pressure numbers go, it depends a lot on how the test was done. Had the engine been sitting and the test was done cold and "dry"? Did they open the throttle butterflies or leave them closed? Was the engines run till warm and the rings were expanded and loaded with oil and cylinder walls "wet" like when the engine is running? Those numbers you received need some qualifying explanation to go along with them for them to have any relevance.

 

[Mustang65fbk]

I think the better option would be a leak down test as opposed to just relying on a compression test. With regards to compression numbers, four strokes are typically up closer to the 200 psi, which six out of the twelve cylinders are in the 130's psi range. And again, a brand new four stroke would be up closer to the 200 psi mark, maybe even slightly more than that. Either way, it sounds like you made the wise decision and walked away as again... it sounds as though the dealer potentially may not be telling you the entire side of the equation. Also, there are a multitude of that same vintage of boat on Boat Trader, of which I'd update your location, add your budget and how much you want to spend, etc, and you can have people on here try and help you out with finding a boat. Good luck with your search!