skyeye

Got a 99 Sonic 26' w/ 500hp carb, (600hrs). While out running today brought the boat back to idle to go under a bridge, then attempted to bring the boat back up to speed, but it would not get on plane. Assuming something was wrong, I lift the hatch to find Milkshake looking oil shooting out of the breather tubes. It was idling quite rough but not cutting out, temps releatively normal but a drop in oil press. I shut it down and got towed in. The engine was running seemingly fine up until this problem yet had a 'ticking' noise which was most prominant at idle and would often go away even at idle after running the boat hard. Had this ticking checked by a mechanic who was baffled and said our options were to "run it till it breaks"- well it seems it did.

I'm wondering what this might likely be caused by, have not flushed the engine within the past few days and checked the oil just a week ago or so. Browsing the similar probs. it looks like I'm looking at cracked intake or exhaust manifold or a gasket- or cracked block. Any ideas as to which one based on the situation- running @ about 3900rpm then down to idle- running fine all day. I live in florida and so has the boat its whole life so I don't think cold weather cracked the block. Help much appriciated!

jbrauer

Early HP500's (like mine and yours) are notorious for broken valve springs and failed head gaskets. If neither has been changed on your motor and you have 600 hours, count your blessings. My guess would be a blown head gasket. Either problem isn't that big of a deal as long as no other damage occured.

Hope you get it back on the water soon!

Jeff

articfriends

If you had a gasket let loose and fill your motor with saltwater you better get it drained,filled and flushed with new oil several times asap,even before you fix the water leak unless your going to pull it and rebuild it,Smitty

Thunderstruck

Just had the same thing happen. It was head gaskets. I've had intake gasket leaks but the milky oil did not ooze out the breathers/dip stick etc. i.e. it takes a LOT of water to give you the symptoms that you had. The head gasket leak will be from pushing the head gasket into the valley near a water jacket. The BBC heads have ONE cylinder on each head that does not have a head bolt between the cylinder and the valley and that is where they break, just happens to be near a water passage. A leakdown test may find the weak cylinder for you but my motor tested OK with the blown head gaskets. The SS ring around the cylinder was intact but a piece of the head gasket was blown into the valley on each head. Pull the intake and look at the intake gaskets, if the intake gaskets are not the problem you should be able to see the part of the head gasket that leaked because a piece will be missing. Good luck

GOODT

Cmi Headers, If Running In Salt Water Check For Pin Holes At The Flange....

Pwrbt33

Sorry for the correction, a big block chevy has 2 cylinders on each side that doesnt have head bolts above the cylinders. Like stated, if you have 600 hrs on a 500 hp, you are way ahead of the game. especially if you never had valve train upgrades done. Like JC said, I would check the head gaskets first, which means do a compression test and a leakdown test. Those cylinder heads can sometimes get pin holes in them in the exhaust ports if there not flushed well also. Even the Gil/Mercury ehaust has failed before do being run in salt water over the years. Does the engine crank over fine? Any noises while cranking?

Keep us up dated...

John

boatn70

skyeye, id like to hear your outcome here.
i, too, have the milky oil out of the breathers on a regular basis, not alot, but it is noticable after a hard run. also, get oil from the dipstick periodically. and if the boat sits after running on a weekend, say 3-4 days i can stick my finger in the oil cap on the VC and feel droplets of water on the rockers. i know this isnt right but i cant get a good reason for it.
i have a "clone" hp500. i built a 502, dart intake,iron heads, etc. i have only 20-30hrs on motor right now!!! should i be tearing this thing down too?
keep us informed skyeye!!!!

rich allen

That much water in short amount of time, I'll go for intake manifold rot as well.
P.S. happened to me as well. Look closely everywhere. Mine popped a hole on its belly, just under where the thermostat housing sits. And get that sh*t out of the motor ASAP.

trivalleyboater

I had this problem with my 502s in Florida. The intake gasket apparently does not like saltwater. I took the intakes off and had a couple gallons of light brown whipped cream. If its the intake gaskets, its not to tough to fix (if thats the only problem). I put new ones in, flushed, changed oil several times and they have been fine ever since. Good luck.

Pwrbt33

boatn70,

Moisture coming from the breathers and on the underside of the valve covers are usually exhaust related leaks such as reversion, broken valve springs, too short of tail pipe low idle or pinholes in manifolds. When your engine oil actually turns milky that usually means something worse.

Keep us posted.

John