1977 Glastron Low compression, spitting oil, clacking sound

[77 gt]

I have a 1977 Glastron with a 140 HP 4 cylinder Mercruiser. Oil has been leaking out of my PCV tube and creating quite a mess on my carb and down the engine block. I have been hearing a clacking sound which I believe is coming from the valves and is only heard under a load or at full throttle. I did a compression test and found that it is very poor 110,70,75,40 (dry) and 125,95,90,45 after squirting oil into the cylinders prior to the test. Both tests were performed while the engine was cold. I recently read a post describing that a person had a blown head gasket which was causing their low compression and replacing it solved their issue... I know I have much more than just low compression going on here, but could all of these issues described above be caused by a blown head gasket? or am I looking at more extensive damage internally? If i have to do a full rebuild would it be more cost effective to do the work or just junk it and buy a new/rebuilt engine? I do pretty well around the garage and could tackle a rebuild but have never done a full rebuild before. Any help or advice would be much appreciated.

Thanks!

Jamie

 

[Bondo]

Re: 1977 Glastron Low compression, spitting oil, clacking sound

Ayuh,.... Welcome Aboard,... It sounds like a completely worn out motor, not Just a head gasket,...

 

[alldodge]

Re: 1977 Glastron Low compression, spitting oil, clacking sound

:welcome: to iboats

Agree, sounds like the motor is worn out. Since you have never done one before I would suggest a new or Reman long block with the conversion kit to up grade it. The kits include an engine, flywheel, exhaust manifold gasket, fuel pump, and coupler as a complete kit.

3.0L Inline 4 Cylinder Engine Kit, Mercruiser (1968-1990) Replacement (#GM181BASE_2M) | Performance Product Technologies

You could pick up the engine other places and then replace the items listed above individually.

 

[Silvertip]

Re: 1977 Glastron Low compression, spitting oil, clacking sound

The clacking would only be due to low oil pressure or wear in the valve train. A head gasket does not cause this noise. Have you checked the oil LEVEL on the dipstick? Low oil level causes low oil pressure but so does severe main, rod, and camshaft bearing wear. If the oil is contaminated with water it will have a light tan milky appearance which is usually associated with a blown head gasket. All of this aside, it would appear the engine does need to be examined to see what's up. Do you know if it overheated? What does the oil pressure gauge read at idle and WOT?

 

[Maclin]

Re: 1977 Glastron Low compression, spitting oil, clacking sound

Having oil coming out of the breathing vents like that, and a low low cylinder compression like that, it is most likely that the low cylinder has bad rings and is letting a lot of the power stroke pressure from that cylinder into the crankcase. If the engine is that worn then the oil pressure is probably low as well due to bearing wear, etc., causing the noises and the engine needs to be rebuilt.

 

[77 gt]

Re: 1977 Glastron Low compression, spitting oil, clacking sound

Thanks for the replies guys. I have checked the oil level each time ive been on the water due to it coming out of the tube and has never been lower than pint or so. No milky oil has been detected and the oil pressure has been 40 at idle and about 50 WOT. Not sure if the engine has ever been over heated as I have only owned the boat for 2 months. The engine runs strong minus these issues described above.

 

[Maclin]

Re: 1977 Glastron Low compression, spitting oil, clacking sound

Take a look at the spark plugs, they usually have a tale to tell.

 

[77 gt]

Re: 1977 Glastron Low compression, spitting oil, clacking sound

That's the wierd thing. Sparkplugs are nice and tan no signs of fouling at all. I expected to find one or more soaked with oil but that wasent the case.

 

[alldodge]

Re: 1977 Glastron Low compression, spitting oil, clacking sound

That's the wierd thing. Sparkplugs are nice and tan no signs of fouling at all. I expected to find one or more soaked with oil but that wasent the case.

All of the combustion pressure is blowing pass the rings and pressurizing the crankcase. The over pressure in the crankcase is pushing oil out the vent tubes. Just my opinion

 

[77 gt]

Re: 1977 Glastron Low compression, spitting oil, clacking sound

Alldodge thanks for the info and link to that web site. Im not sure which would be more cost effective though rebuild myself or buy a block. I have 5 months till summer so I guess I have the time

 

[MarkSee]

Re: 1977 Glastron Low compression, spitting oil, clacking sound

Seems like if you've only had it 2 months and no history on the engine then you'd have no idea if it's been rebuilt 1 or more times already to know if it's even capable of a(nother) rebuild.

Probably depends on what you find when take it apart and your skill/comfort level (you indicated never having done a full rebuild before), access to tools, or close friends to help, or a shop that might do a watch-and-learn on which route to go.

Mark