Powerboat Forums at SpeedWake banner

1 - 20 of 23 Posts

·
Registered
Joined
·
36 Posts
Discussion Starter · #1 · (Edited)
Pulled the dipstick yesterday and got milky oil.

Engine oil was changed at the beginning of season, boat has been ran 4 times since then without any problems.

Engine has been running just fine, absolutely no problems and wouldnt have noticed anything without checking the dipstick. It was ran on a hose /muffs before last outing and the muffs fell off, had to replace impeller - don't think it overheated, wasnt that long and only at idle, but not sure.

1987 5.7 350, 4 barrel carb, engine was rebuilt 2 yrs ago by previous owner. thru prop exhaust.

My question is where to start....I've done some reading and am looking at exhaust gaskets being the first place to check, then head gasket, also intake. Have never worked on boat engines before, but I'm ready to get this thing back in the water.

Thanks for the help in advance.
 

·
Registered
Joined
·
58 Posts
tcgravy said:
Pulled the dipstick yesterday and got milky oil.

Engine oil was changed at the beginning of season, boat has been ran 4 times since then without any problems.

Engine has been running just fine, absolutely no problems and wouldnt have noticed anything without checking the dipstick. It was ran on a hose /muffs before last outing and the muffs fell off, had to replace impeller - don't think it overheated, wasnt that long and only at idle, but not sure.

1987 5.7 350, 4 barrel carb, engine was rebuilt 2 yrs ago by previous owner. thru prop exhaust.

My question is where to start....I've done some reading and am looking at exhaust gaskets being the first place to check, then head gasket, also intake. Have never worked on boat engines before, but I'm ready to get this thing back in the water.

Thanks for the help in advance.
Do you have aluminum valve covers? The shop that built my big block said not to run aluminum valve covers because they can cause condinsation from our cold water in the northeast, early in the season, cold water? just a thought!
 

·
Registered
Joined
·
36 Posts
Discussion Starter · #5 ·
Anyone have any easy suggestions for pressure testing the exhaust (manifolds and risers)?

Or any tips on what to look for if something is wrong with those? Have read that its near impossible to see, need to pressure test it.

Manifolds/risers are as old as the boat (20 yrs) as far as I know. Probably time to replace em, eh?
 

·
Registered
Joined
·
252 Posts
I had my CMI Headers pressure tested by CMI... From what they explained to me, it is fairly easy. They submerge the headers in a tank and apply pressure. I don't think they put too much pressure (30-40 PSI max). I'm still questioning how to handle a potential water reversion problem, so if I call them I'll specifically ask for both our needs.
 

·
Registered
Joined
·
36 Posts
Discussion Starter · #8 ·
Update:

Compression test revealed good compression (around 150) for all cylinders except cylinder #5

pressure test revealed a cooling system leak into cylinder #3



Any thoughts?
 

·
Registered
Joined
·
252 Posts
You want to do a Compression and a Leakdown test. You can have good compression but a bad leakdown. I had a shop tell me my engine was good all I needed to do was find my oil leak. Then the engine rebuild shop did a leak down test and found we had some bigger problems.
 

·
Registered
Joined
·
36 Posts
Discussion Starter · #11 ·
Head disassembled today:

Found a break in the head gasket near a water/cooling hole in cylinder #3. Also found a decent puddle of water there in #3. No water in cylinder #5, but the piston does seem to have some buildup on its crown.

Pistons/Cylinder walls in #1 and #7 look and feel perfect.

Also, after disassembling the manifolds/risers checked on the flapper on that side - flapper is obviously broken, one side of it is completely missing, meaning about half of it is still there.

Currently planning on replacing the head gasket and the flapper...changing oil again...checking...and hoping for the best. Any other thoughts on things that need to be done?

Any ideas on what is going on with cylinder #5? (low compression, 90) Put oil into the cylinder (before tear down), turned it over, and compression didnt change. This points to valves, not rings, but could it be something else?
 

·
Registered
Joined
·
3,516 Posts
tcgravy said:
Head disassembled today:

No water in cylinder #5, but the piston does seem to have some buildup on its crown.

Any ideas on what is going on with cylinder #5? (low compression, 90) Put oil into the cylinder (before tear down), turned it over, and compression didnt change. This points to valves, not rings, but could it be something else?
I would check out All the valves , seats & guides and also check the push rods for staightness, and the rocker studs if their press fit, if you had any hydraulicking. since now is the time to be thorough while it's apart..
 

·
Registered
Joined
·
36 Posts
Discussion Starter · #13 ·
Agree....

not really sure how to "check" the valves though??? Take them apart and check em out? Head is off, just don't know how/what to check...

What is to be looked for regarding the valves, seats, and guides?
 

·
Registered
Joined
·
3,516 Posts
Yes, remove the valve springs & retainers, shims (if any)and keep Everything in exact order, as you remove everything, all you can do is do a visual check for now, unless you have all the necessary tools, ie; magnaflux kit, concentric valve seat indictor, mic's, telescopic bore gages, spring pressure tester, etc..in other words, machine shop stuff.
But you can do some easy checking, like, before you remove a valve, after the spring is off, push the valve a little off it's seat and wiggle it side to side, against the valve guide, and feel for excessive play or bind..(the valve guide could be your culprit to a valve not seating correctly) then pull the valve out and look at the seating surfaces, it should have very even wear all around, and somewhat shiny & smooth. then look at the stem, it should be smooth & shinny bright where it travels in the guide, then look at the valve seat on the head, again it should have very even wear and look for signs of burning and heat discoloration on the exhaust seating surfaces, then look for cracks on the seat, although this is more common on sbc and usually at the thinest part, between the intake & exhaust areas, but most cracks can go un-noticed, that's where magnafluxing comes in...
So if you do see anything obvious as mentioned, it's time to take them to a machine shop..and have them throughly checked over.. and Oh, assemble everything back together before you drop them off if you do.
Good luck,
 

·
Registered
Joined
·
36 Posts
Discussion Starter · #15 ·
Thanks for the help so far....

did a visual / touch test of everything and didn't find anything wrong with valves or head.

It is now mostly back together, still needs manifold put on and timing re-adjusted, flapper also needs to be replaced.

Question - does anyone know a good place to buy these flappers? They are $48 from a Merc dealer, and that seems excessive.
 

·
Registered
Joined
·
3,516 Posts
If the valves checked out OK, maybe you had some compression loss due to the head gasket, so do another compression check on # 5 to confirm if it was the culprit, if it's still low, then do a leak down check on it.
 

·
Registered
Joined
·
36 Posts
Discussion Starter · #17 ·
Yea - leak down on #5 revealed leaking through the carb, meaning its something with the intake valve on that cylinder.

Probably not going to get fixed until summer is over....

thanks for the help guys
 

·
You BLOT that schit!
Joined
·
2,692 Posts
tcgravy said:
Yea - leak down on #5 revealed leaking through the carb, meaning its something with the intake valve on that cylinder.

Probably not going to get fixed until summer is over....

thanks for the help guys
You can pull the manifold and head, have it ground and replace the bad seat/valve for around $200.00 total including the machine work. I wouldn't ruing the whole season over that.
 

·
Registered
Joined
·
36 Posts
Discussion Starter · #19 ·
Pulled the head and am having it re-surfaced and replacing valves on the low compression cylinder.

Someone mentioned to me that I may want to change both head gaskets while I'm at it, or the other one is going to blow shortly here after. Any opinions on this?
 

·
Registered
Joined
·
3,516 Posts
Yes, I would do them both now, just a little more to take apart, but I think it would be well worth it, just for the piece of mind knowing it's done.
 
1 - 20 of 23 Posts
Top