1999 4.3L Mercruiser Consuming Oil (Some Diagnostics Done-What Next?)

[Gus-SeaRay]

I have a 1999 185 Sea Ray with a 4.3L carbed engine. It is consuming a lot of oil. On a 3 hour outing with some starts and stops a couple of WOT runs for a minute or so the engine consumed a little over 1/2 a quart of oil. I see smoke at start up and after sitting then start up again. Don't notice smoke much when it is in the water. But when on the muffs I can see a little bit of whitish smoke coming out of the exhaust. Also see whitish smoke coming out of the flex pipes that go from the valve cover to the breather. Observed sooty black oil deposit on the outside of the breather where the flex pipes stop. I have done the following test with results.

Compression Test
#6 165
#5 175
#4 173
#3 173
#2 175
#1 178
Re-Tested #6 after seeing it as the low one and got 182 2nd time around.

Leak Down Test. Compressor regulator set at 90psi. 1st number is left gauge on leak down tester / 2nd number is right gauge going to cylinder on tester.
#6 77.5 / 68 = 12.3%
#5 79 / 78 = 1.3%
#4 77 / 67 = 13%
#3 79 / 78 = 1.3%
#2 78 / 71 = 9%
#1 79 / 76 = 4%

Vacuum Test on Manifold
Snap shot attached. This showed good/normal vacuum however with the needle fluttering fast by a small amount.

Some background on the recent findings.

Engine cooling system: I recently replaced the sea water pump, exhaust manifolds and risers because I noticed that the starboard exhaust elbow was getting up to 180+ while the port was running 130 or so. Replaced the engine water pump when I first got it 4 years ago.
--> With a 160deg stat in the boat will not hold a consistent temperature it fluctuates abrubtly between 178 and about 200. Constantly going up and down between 180 and 200.
--> With a 142 deg stat in the boat it holds a consistent temperature at 158 no matter how it is loaded. Stays right there.

Drive/Prop: I have had the boat for 4 seasons and recently realized that the boat likely has had the out drive swapped out because it has a 1.65 gear set and is over propped. WOT is 4000 rpm at 42.6mph on gps.

I have replaced the valve stem seals but really didn't find a difference in the oil consumption... While replacing the valve stem seals I could feel play/wiggle in the stem to guide but each seemed consistent. I did not have a way to measure the movement at the time of replacing the seals.

All that is background at where I am now. I am trying to make a decision about replacing the heads (about $300) or replacing the long block (about $1500).

Questions:
- Am I right in saying based on the compression, leak down and vacuum test that the engine seems healthy?
- I think the tests are pointing to the valve guides being worn. Does it make since that only valve guides would be worn and not the lower end? Or should these be expected to wear at the same rate?
- Is the fact that the engine will not hold consistent temp with a 160 deg stat trump all of the other test and indicate there is something going on in the engine that merits replacing the long block?
- Ultimately should I consider replacing only the heads or should I replace the long block?

Thank you for your time and input!
Gus

 

[alldodge]

Compression Test
#6 165
#5 175
#4 173
#3 173
#2 175
#1 178
Re-Tested #6 after seeing it as the low one and got 182 2nd time around.

My initial thoughts is the motor has been rebuilt and done wrong, or you have a bad gauge. Compression above 150 psi would indicate liquid in the cylinders. If it was rebuilt with dome pistons and milled head, then compression would be way up.

If compression is real high as shown, the rings may not be able to hold it all and its leaking past them.

The temp issue may be from when the 160 stat is used, your getting some preignition

Check compression with another gauge and if it comes up the same, then I would pull the heads and see what things look like

 

[Lou C]

Your comp test results look good and I don’t think your leak down is bad either. The wear in the valve guides could be a culprit in the oil consumption issue. I’d consider taking off the heads and taking them to a good machine shop to get checked out. I did this on my 4.3 and it’s not a bad job at all.

 

[Lou C]

PS before and after replacing the heads my 4.3 comp tests were in the range of 160-165 so 170 is not out of what you might expect.

 

[QBhoy]

I’d maybe add that white smoke (outwith just being steam) usually means unburnt fuel..not burning oil.
to add to that though. Unburnt fuel washing down the bores can lower compression and burn off oil. Only thing is that usually the oil would thin and stink of fuel too. This is usually a symptom of running these engines at idle for long periods. Poor combustion and not being up to temp makes it really noticeable.
loosing that much oil though. That’s something else maybe. I’d think you’d really notice a load of blue smoke and smell it easily too.

 

[Rick Stephens]

I would bet guide seals as well. Have had that issue. They ride up and start wearing as they get pushed up and down on and off the guide.

 

[Lou C]

PS in my OMC shop manual the comp test specs given for the GM 4.3 is 160-175. So you're right in the correct range.

 

[Gus-SeaRay]

Thank you for the help! Sounds like next step is to pull the heads.

 

[Lou C]

In my case my old heads had cracks in the center cyls exhaust seat area (probably from a bad overheat in the past) and the cooling passages were eroded from 15+ years of raw water cooling in salt water. What made the repairs necessary was that the engine blew both head gaskets at the end of the 2016 season and I had water in 2 cyls. So the machine shop suggested replacing the heads with a pair of reman marine V6 heads and that’s what I wound up doing. $550 for the pair and about $120 for a set of Fel Pro marine gaskets. So far it worked out well the engine runs better and with the new center riser exhaust I installed it runs cooler as well vs the original one piece batwing exhaust.

 

[Howard Sterndrive]

Did anyone ask what oil we're using? 25W40?

 

[Scott Danforth]

No need to pull heads, get right valve spring compressor and change valve seals with heads on. Either the lever type or the screw type

check your gauge, compression numbers should be around 150.

 

[Gus-SeaRay]

Confirmed using quicksilver 25w40. Also have replaced the valve guide seals with the style with full metal jacket/umbrella. I am going to put a lower pitch prop on and do some running to recheck oil consumption. I changed the oil and ran it again today on muffs and just don’t see any clouds of smoke. The engine runs so good it’s not an obvious move yet to me to pull the motor. But it if continues to consume will have to decide if it is worth pulling the heads while in the boat or pull the entire engine to go through it...

 

[Gus-SeaRay]

These are pics of the plugs early in the day.

 

[Gus-SeaRay]

Using a dial indicator on the intake valve stem of cylinder #6 I got a max of just under .005" movement.

 

[Scott06]

One thought given your vacuum guage comment about it hunting around could intake gasket be sucking oil into intake port from lifter valley?

 

[QBhoy]

Oil smell of fuel ?

 

[Rick Stephens]

Hmm, mostly, if your guides are worn badly, your vacuum gauge will be jumping like a mexican jumping bean. They also will allow quite a bit of oil by. You have one cylinder that the spark plug shows fouling. So maybe. I agree with you that if your oil pressure is fine, and the motor runs really well, have to think on it before just tearing it down. Depends on how you feel about it, I guess.

BTW, if you have the lift capability, pulling a motor is much much easier than pulling heads in the boat. I own a tractor and it takes me about half hour to be putting the motor on a motor stand to work on it. Makes everything go easier working on it there than in the boat.

 

[Lou C]

It depends on how you feel about having to be vigilant about checking oil often and having to add oil. On an older engine that is not really a big deal, it would only be if someone who was using the boat never checked the oil. Actually removing the heads with then engine in the boat for me was not difficult, maybe because my boat had the wide open engine compartment no molded in 'glass on the sides for jump seats. The only thing that was a bit difficult was getting the intake manifold off because the original gaskets were baked on like Kryptonite. The bolts for both heads came right out surprisingly easily (with my De Walt 1/2" drive electric impact gun) even with 15+ years of raw water cooling in salt water. If you had all 6 plugs getting oil fouled to the point where the engine wouldn't run right that would be one thing but you're not at that point at all. So it really is your choice. It's not a bad job, the Chevy small block series is a great engine for the do it yourselfer because of the simple basic design and wide availability of inexpensive parts.

In my case of course I had to take it apart due to the blown head gaskets but it had been using oil for quite some time. I usually had to add approx. 1-2 qts over the course of the summer and my plugs would eventually start to look somewhat oil fouled. I'm sure my old heads had sloppy valve guides and the seals were in need of replacement. Since the machine shop found that the center cyls had cracks in the exhaust valve seat area and the cooling passages were getting eroded due to raw water cooling in salt for 15+ years replacement with re-man heads was the best plan....

 

[Gus-SeaRay]

Yes I do think the oil smells of fuel.

 

[Lou C]

Which carb do you have on that 4.3? 2bbl or 4bbl? Is the choke opening all the way? (must be an electric choke). Your plugs look very good except that one, so I'd be surprised if you have fuel dilution in the oil. About the only things that would cause fuel dilution would be a choke that does not open (but then we'd expect all the plugs to be black) or a sticky float/leaky needle valve that is allowing flooding. I do recall hearing that the 4bbl Webers that Merc used in some years were prone to that.