WHat do you think of these compression results?

[CougarJackson]

350 MAG MPI / 250 hours

1: 190
2: 180
3: 170
4: 175
5: 167
6: 175
7: 180
8: 180

Looking at buying a 2006 Crowline 262 EX and these were the results. Thoughts?

 

[MWG2600]

Re: WHat do you think of these compression results?

Something is wrong with it, 167 on 5, 190 on 1. To much diffrance.

 

[tpenfield]

Re: WHat do you think of these compression results?

Yes, I'm looking at #3 & #5, which are right next to each other . . . This would warrant a cylinder leak test just to shed a bit more light on the differences.

The results are OK, but not 'good'. Figuring your 'nominal'/'typical' cylinder is 180, then you are looking at a 'good' range of 189 - 171. so, you have 1 or 2 cylinders that are falling just outside that range. . . #3 & #5.

Was the engine well warmed up when the test was run? If not, then maybe a re-test to see if you get a difference.

Also, are there sea trial results to evaluate, such as WOT rpm, etc. ???

 

[CougarJackson]

Re: WHat do you think of these compression results?

Not sure...the dealer selling the boat performed the test.

When I worked on cars, my rule of thumb was less than 15% was acceptable. Is there a difference with marine motors?

 

[matt167]

Re: WHat do you think of these compression results?

3 and 5 are togther on a SBC as Ted said. Likely has a head gasket issue between the 2. Not enough to be noticeable, but there. It usually indicates a leak between cylinders and is actually common between 3/5 and 6/4 on SBC's ( not limited to marine environments ). Sometimes it's bad enough that both cylinders register less than 100 or even zero and the engine drops 2 cylinders.

I would make the dealer run a leak down test on at least 3,5,6 and 4 so you get readings to compare to

 

[tpenfield]

Re: WHat do you think of these compression results?

Yes, a 15% spread (instead of 10%) would put #5 just inside the range . . . the fact that the 2 lowest are right next to each other would be the cause to investigate further.

 

[CougarJackson]

Re: WHat do you think of these compression results?

So what are we looking for on the leakdown test? Just percentage? Bubbles in oil? Raising of coolant level? Presumably we are not looking for hissing sounds in the intake or exhaust.

 

[matt167]

Re: WHat do you think of these compression results?

leak down percentage+ hiss. If it's leaking between cylinders as I would suspect, then you will get hissing from the opposite cylinder as one of those valves would be open.

 

[Don S]

Re: WHat do you think of these compression results?

When was the last time the engine ran? It hadn't been sitting for several weeks before the test was it?

If the engine hasn't run for a long time before doing the compression test, a little bit of rust on the open valves would lower the compression on an engine, even the best engine in the world. At least start it and run it for 2 or 3 minutes before doing a compression test. Then you know the numbers will mean something.

The compression numbers you posted, does the number in your original post coincide with the number of the cylinder, or are those numbers just a list of 8 numbers no particular order?

 

[tpenfield]

Re: WHat do you think of these compression results?

So what are we looking for on the leakdown test? Just percentage? Bubbles in oil? Raising of coolant level? Presumably we are not looking for hissing sounds in the intake or exhaust.

Really looking for 2 things . . .

1) the amount of leak . . . Under 10% would be fine , 10-15% would be fair, 20-30% = poor, over 30% = bad

2) Where it is leaking from (for the ones that are not 'fine').

(crankcase = rings)
(intake or exhaust = respective valve)
(Other cylinder (as Matt indicated) or cooling system) = head gasket

As a sample . . . Here are the results from my 454 just after a valve job:

Cylinder / Leak Percentage
________________________________
Left 1 = 8%
Left 3 = 1%
Left 5 = 1%
Left 7 = 3%

Right 2 = 6%
Right 4 = 6%
Right 6 = 2%
Right 8 = 6%
_________________________________

 

[CougarJackson]

Re: WHat do you think of these compression results?

The boat had been sitting for a bit, not sure how long. The engine was warm at best. We took it out for a 5 minute ride, then it sat for an hour or 2 and then they did it. This was Saturday. We were old it would be done again on Monday and then today they sent us those numbers. We were under the impression that these numbers were from the retest, but evidently, the numbers they gave today was from the same test on Saturday. SOoooooo, they are going to run the motor for a bit right now and retest and send the numbers.

Don, those numbers are cylinder numbers.

 

[tpenfield]

Re: WHat do you think of these compression results?

Here are the results of my 454 before the valve job . . . the compression is not too bad, but when you look at the leakage, it is much more revealing.

Cylinder------ Pct Leak------ Compression
L1-----------------8 %-------- 135
L3----------------35 %-------- 135
L5----------------48 %-------- 131
L7----------------17 %-------- 137
R2----------------11 %-------- 137
R4----------------52 %-------- 127
R6----------------37 %-------- 132
R8-----------------8 %-------- 142

I had to replace the valve seats on #4 and #5, the rest just needed to be ground a bit.

 

[Don S]

Re: WHat do you think of these compression results?

Did you test run the boat? How did it run? any problems?
Personally, for a 2006 boat, I wouldn't worry about it a bit.
You could even try another compression test, maybe the 190 was a false reading.

Here is the service bulletin from 97 on what Merc (and on GM since the info came from GM) allows as far as compression variation.

View attachment 97-25 Compression Test.pdf

 

[CougarJackson]

Re: WHat do you think of these compression results?

The dealer is redoing the test right now, so we shall see...just piece of mind, you know?

Are you sure you attached the correct document? It looks to be about a no start problem.

 

[Don S]

Re: WHat do you think of these compression results?

Hmmm, wrong one for some reason try this one.

View attachment 97-25 Compression Test.pdf

 

[CougarJackson]

Re: WHat do you think of these compression results?

And the boat took a couple tries to start (presumably cause it has been sitting for a while), but other than that, it SEEMED to run fine.

 

[CougarJackson]

Re: WHat do you think of these compression results?

Thanks, Don. Looks like we are ok. Just waiting on the retest results from the dealer.

 

[tpenfield]

Re: WHat do you think of these compression results?

And the boat took a couple tries to start (presumably cause it has been sitting for a while), but other than that, it SEEMED to run fine.

The service bulletin gives a fairly wide range for acceptable compression test results. In this case your range would be as low as 133 psi. You probably would not accept that though, if you had some cylinders at 180-190 and others in the 130's. so, it is a judgement call that you have to make.

When you sea trailed, did you take it up to WOT and record the rpm that the engine reached.?

when I bought my boat recently the cylinders were +/- 7% , so I thought it was ok, since the engines reached their WOT rpm spec. If they had not, then it might have been worthy of some more testing, etc.

 

[CougarJackson]

Re: WHat do you think of these compression results?

I did not take note :-(

 

[CougarJackson]

Re: WHat do you think of these compression results?

Numbers came back in the 180 range so we are good to go.