Compression Test results

Richeskis

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Jan 1, 2011
Messages
13
Hello Everyone.

I just did a compression test due to finding water in the oil after I did a oil change on a 5.7 mercruiser. I was hoping the water was from the garden hose and suction cups that I was using to get cooling water to the motor during the time to heat the oil up before pulling the oil out, I left the hose on when the motor was not running so I think I pushed water into the oil, but to make sure I did a compression test to make sure no head gasket failure.

here is the numbers, left side head # 1 180 psi, # 3 160 psi, # 5 150 psi, # 7 160 psi,
Right side head, # 2 120 psi, # 4 150 PSI, # 6 160 PSI and # 8 140 PSI

I hope that the # 2 being lower then the others is not from a blown head gasket
any inout would help.

Thanks

Rich
 

tractoman

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Jul 16, 2009
Messages
370
Re: Compression Test results

That is a lot of variance between cylinders. Was this engine warm or cold, and did you have the throttle plates fully open? How did this thing run? It seems like it would have had a noticable miss.
 

Don S

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62,321
Re: Compression Test results

How much water in the oil are we talking about? How far over the full line is the oil on the dipstick. Is the oil milky?
Very seldom does a blown head gasket allow water into the oil on a marine engine.
 

Bondo

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Re: Compression Test results

I was hoping the water was from the garden hose and suction cups that I was using to get cooling water to the motor during the time to heat the oil up before pulling the oil out, I left the hose on when the motor was not running so I think I pushed water into the oil,

Ayuh,... Leaving the water flowing, without the motor running will Not put water in the oil....
A Blown headgasket generally ain't a cause either....

While #2 is abit low, it has nothing to do with water in the oil...
A leak-down test might tell ya Why it's low though...

Draining the cooling system, isolating the block, 'n pressurizing with Air will tell you more about Why there's water in the oil....
 

artificialreef

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Feb 21, 2009
Messages
504
Re: Compression Test results

Those are not good results. If you are going to pull the heads for a head gasket you might as well send them off to a machine shop to at least be checked for cracks. Or if you can afford recondition.
 

TilliamWe

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Re: Compression Test results

Listen to Don and Bond-o. It is probably NOT a head gasket.
 

Richeskis

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Messages
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Re: Compression Test results

Before I did the oil change I check the oil level it was normal, right on the full line on the stick, oil looked normal, black, put the water cups on the outdrive, turned the hose on, and then started cranking the motor, it took a while to fire and keep running as it had not run sense last Sept, and the Holley Carb does not have a choke plate, so it can take a few tries to get it to idle, once its stared to run and Idle I let it run for 10 min to heat up the oil like I have done year in year out never had a problem, once the ten min was up turned off the motor and started pump out with oil pump out motor, the oil came out looking brown like it had water in it, and the filter oil looked the same, never had this happened, other times it came out nice black, so I figured I would do the compression test, as the motor has been running great...I pulled all the interior so I can get to the normal drain plug and drained out the rest if the oil, it was brown, I have re-added the oil and changed the filter, I just would like to know I have a bigger before summer and find I am doing a major repair during the boating season.
 

Richeskis

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Re: Compression Test results

When, I did the compression test, the motor was cold, and throttle plates were closed. the oil look, brown and milky after warming up the motor to do the oil change, before worming up it was black, like always, motor never burns oil, so the level is always good.
 

tractoman

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Jul 16, 2009
Messages
370
Re: Compression Test results

Where are you located and did you winterize this engine. It seems that you may have a crack somewhere letting water into the oil. You can try to run it a little and keep changing the oil, but I think you've got something wrong that needs attention.
 

cr2k

Captain
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Mar 19, 2009
Messages
3,730
Re: Compression Test results

"oil looked normal, black," Black is not normal for oil unless you run it way too long between changes.

Compression test is done with engine warm, throttle fully open and at least 6 compression strokes per cylinder. You this procedure for comparison your results may vary.
 

Richeskis

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Re: Compression Test results

I am located in North AZ, By Lake Havasu, I should say the oil looked the same as it has in the past when I went to change the oil, I give it a change before each summer season, so it maybe to long between oil change. I will heat up the motor and re-do the compression test.
 

Bondo

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Re: Compression Test results

I will heat up the motor and re-do the compression test.

Ayuh,.... Oil Level, Vs. oil Color.... The Color is kinda irrevelant as if the Level isn't rising, it's Not water....
And,...
A Compression Test is Totally irrevelant to Water in the Oil....

Check the oil Level,....
Fire up the motor, 'n go Boatin' for a few hours....
Has the oil Level risen,..??
If Not, you don't have a Problem....
If it Has,...
Drain the cooling system, 'n pressurize It, then follow the Sound to the Crack in the Block.....
 

Richeskis

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Re: Compression Test results

Hello Bond - O and everyone.
OK, before the first oil change ( normal per-season oil change ) oil level normal. and we used the boat allot during the season. OK, hooked up the water suction cups on the out-drive and turned on the water, it took about 5 min to get it started, due to Holley and no choke, once it started ran for 10 min to get the oil hot, pump the oil out with the Stern oil pump out system, that connects to the oil dip stick tube, when it came out it was brown and milky, like it had water in it, filter was the same brown and milky, and with the oil pump out system using dip stick tube, you never get all the old oil out, I did not have time to do any more investigation, as the boat is keep at our 2nd home. so I added the new oil and filter and let it sit ( figured it was better to have new oil with some of the old milky oil as it sat) now this weekend, took all the interior out to give me access to the drain plug at the bottom of the oil pan, drain all the oil out, (let it drain all night ) added new oil and filter and checked compression, ( first readings motor cold ) then started motor with suction cups on out-drive and heated up for 2 min, this time waited until motor was running before I turned on the water to the suction cups and taken drain oil, no sign of any new water in oil, just some signs of not getting all the old oil out during the 2nd oil drain, now this makes 3 oil changes and filters, must say oil looks nice and new, never looked this good after an oil change, with the 3 oil change and all the oil new and new filter, I put the suction cups back on the out-drive, started motor and turned water on once motor was running, ran motor for 10 min, like the first time, after motor run, oil still looks like new on dip stick, no sign of water in oil, and did a compression check with motor warm and throttle wide open.
warm compression check numbers, Left head # 1, 205 PSI, # 3 190 PSI, # 5 190 PSI, # 7 200 PSI, right head, # 2 150 PSI, # 4 180 PSI, # 6 190 PSI and # 8 190 PSI, you guys seem to be a lot of help and I am guessing I am OK but would like your option.
 

Bondo

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Re: Compression Test results

Hello Bond - O and everyone.
OK, before the first oil change ( normal per-season oil change ) oil level normal. and we used the boat allot during the season. OK, hooked up the water suction cups on the out-drive and turned on the water, it took about 5 min to get it started, due to Holley and no choke, once it started ran for 10 min to get the oil hot, pump the oil out with the Stern oil pump out system, that connects to the oil dip stick tube, when it came out it was brown and milky, like it had water in it, filter was the same brown and milky, and with the oil pump out system using dip stick tube, you never get all the old oil out, I did not have time to do any more investigation, as the boat is keep at our 2nd home. so I added the new oil and filter and let it sit ( figured it was better to have new oil with some of the old milky oil as it sat) now this weekend, took all the interior out to give me access to the drain plug at the bottom of the oil pan, drain all the oil out, (let it drain all night ) added new oil and filter and checked compression, ( first readings motor cold ) then started motor with suction cups on out-drive and heated up for 2 min, this time waited until motor was running before I turned on the water to the suction cups and taken drain oil, no sign of any new water in oil, just some signs of not getting all the old oil out during the 2nd oil drain, now this makes 3 oil changes and filters, must say oil looks nice and new, never looked this good after an oil change, with the 3 oil change and all the oil new and new filter, I put the suction cups back on the out-drive, started motor and turned water on once motor was running, ran motor for 10 min, like the first time, after motor run, oil still looks like new on dip stick, no sign of water in oil, and did a compression check with motor warm and throttle wide open.
warm compression check numbers, Left head # 1, 205 PSI, # 3 190 PSI, # 5 190 PSI, # 7 200 PSI, right head, # 2 150 PSI, # 4 180 PSI, # 6 190 PSI and # 8 190 PSI, you guys seem to be a lot of help and I am guessing I am OK but would like your option.

Ayuh,... I'd think all ya gotta do now is Change out the Impeller, 'n I'd throw in the Housing kit too....

The motor shouldn't even be cranked on the starter, Without water flowing through the Muffs....
And,...
What's with the Holley,..?? What else on this motor Ain't Mercruiser,..??
 

Richeskis

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Messages
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Re: Compression Test results

The impeller and housing is on my off season service plans, I also need to do the trim sensor switch, but figured I would take it in for that repair, do you know if they take the out-dive apart for that or does it come out in one piece, I know it has to come off the boat to do the replacement right, I replaced it one time by using water tight butt connectors, but seemed to fail fast after that repair, if they take the out-dive apart, then I will have them do the impeller and housing at the same time.

The motor has MDS ignition and the Holley, the heads have be reworked, ported, polished, sized up valves, and new roller tipped rockers. went from 1.5 to 1.6, my friend who did race motors, and worked on Corvettes, he always said that you don't need a choke on a Holley, it was completely tuned to the motor years ago, but it is in need of rebuilding this off season too ( my friend had the heads done then too, years ago, he passed away a few years ago, so, I lost a friend and some one with great motor knowledge )
 

Bondo

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Re: Compression Test results

The motor has MDS ignition and the Holley,

Ayuh,... Are those Marine rated components,..??

If Not,... You've got a BOMB lookin' for a reason to Explode...
 

Richeskis

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Jan 1, 2011
Messages
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Re: Compression Test results

All Marine rated, MSD and Holley, the heads are orginal but just re-worked do to two valve failures.
 

TilliamWe

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Re: Compression Test results

All Marine rated, MSD and Holley, the heads are orginal but just re-worked do to two valve failures.

Oh boy, here we go. A "Race car motor guy" did all this work? I don't like where this is going.
 

artificialreef

Chief Petty Officer
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Feb 21, 2009
Messages
504
Re: Compression Test results

If that wasnt a 5.7 i would still say #2 is low. 10% of 150 is 15lbs. 150 plus 15= 165lbs. The next nearest is what 180. Thats 20%. Something to keep an eye on. Not saying you need a rebuild. If it was mine i would run it. That dang sb may run forever like that.
 

GLENN M

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Aug 14, 2010
Messages
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Re: Compression Test results

on all out race efforts we machine choke tower off our holleys,does it help, for hood clearance thats about all. but these are 4150 and or 4160 high perf models,these carbs have to be set up ie;power valve,jets accelerater pump shot how much and duration among others,these arnt marine carbs.so you must have a replacement carb for a specific motor setup.the fact that its so hard to start tells you you need the choke,without choke you have to pump throttle ten times then fire it.make sure it is marine carb you dont want to gamble especialy with a holley and peoples lives, goodluck.
 
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