2001 Mercruiser 3.0L - Compression Test Results

[phishvt]

Hello all,

Recently I've been having trouble with my 2001 Mercruiser 3.0L. The engine runs ok in the mid-range RPMs, but at WOT it will run for as long as a minute and then gradually drop in RPMS until it reaches 4000 RPM ... once it even went all the way back to idle and then stalled.

We had a compression test done and the results are as follows:

Cyl 1 - 180
Cyl 2 - 135
Cyl 3 - 0
Cyl 4 - 120

I've browsed through the forums and seen various posts that indicate that a head gasket would typically affect compression in two adjacent cylinders. Any ideas what would affect just one cylinder? Is a leakdown test the next step? My mechanic wants to yank the head and is already suggesting a rebuilt motor.

Thanks!

 

[scooter4n]

Re: 2001 Mercruiser 3.0L - Compression Test Results

you can start with head gasket, do it yourself ( not that bad) and save you little $$.
Start from there, you never know. This can be it.

 

[Haut Medoc]

Re: 2001 Mercruiser 3.0L - Compression Test Results

Bad valve, hole in piston.......
Pull the valve cover & see if there is anything obviously wrong with the rocker arms or springs on that cylinder......
You will most likely need to pull the head though.......​

 

[tommays]

Re: 2001 Mercruiser 3.0L - Compression Test Results

With a 0 you can do the leakdown test but it is likely that there will be an easy to see problem with the head removed




Tommays

 

[Dante04SRT]

Re: 2001 Mercruiser 3.0L - Compression Test Results

The head on the 3.0 is VERY easy to remove - I did it complete from start to finish in ~1 hour, never having done it before on this motor.

 

[Redneck Yacht Club]

Re: 2001 Mercruiser 3.0L - Compression Test Results

Any water on the plugs? Is it an saltwater motor? Whens the last time ya had the exhaust elbow check? Finding the problem is easy, finding cause can tricky Ya need to ask more questions at your dealership. One problem cost alot but the cause can cost alot more.

 

[phishvt]

Re: 2001 Mercruiser 3.0L - Compression Test Results

Here's what she looks like with her head torn off:

Note the upper-right section of piston #4.

Thanks for the follow up post guys. Looks like we're going to get a rebuilt engine.

Redneck Yacht Club: It is a salt water motor but has the freshwater cooling system. I don't believe there was any water on the plugs.

 

[Don S]

Re: 2001 Mercruiser 3.0L - Compression Test Results

Has the timing been change any time you know of? If it was changed, was it put into base timing mode before setting? Did the advance work?
The newer 3.0L engines with the EST distributor are VERY VERY, particular about timing and must be set exactly. 2? can blow a head gasket.

BTW, the intake valve on #3 is tulliped. That is why you have 0 compression, not the head gasket.

 

[Redneck Yacht Club]

Re: 2001 Mercruiser 3.0L - Compression Test Results

Yep thats a tulliped valve, your lucky that didn't break off.
Plugs look lean too.
And when ya get the head redone, ya need to set the BASE timing.
Some of those 3.0 LT's have different base timing too.
Their is a sticker on your engine cover that tell ya your base timing.
After ya do that, run the motor in the water and recheck timing with a lite.

 

[newboater2day]

Re: 2001 Mercruiser 3.0L - Compression Test Results

hello i have a 89 searay with the 3.0 mercruiser i been haven trouble with low rmp i have changed everyhing and talk to a searay dealer and they told me to check my compression sounded like i have a blow head gasket so i did my compression was

1-90

2-30

3-30

4-80

is this the sign of a blow gasket or not? if so how hard is it to change and also i was reading something about the timming how the best way to check and st the timing? please reply

 

[Coors]

Re: 2001 Mercruiser 3.0L - Compression Test Results

Engine needs replaced, it is worn out.

 

[Don S]

Re: 2001 Mercruiser 3.0L - Compression Test Results

Start a new thread with your question newboater2day.
This thread is about the original posters problem.