470 mercruiser water in oil, steam coming from valve cover

[nathant]

hey gents,
First post for this forum. i can probably imagine how many times this has been asked but im going to ask anyway.
so i have a 1986 470 mercruiser in a 22 foot Caribbean commodore that i recently purchased at a very good price, when i first got the boat it was having issues with heating and water contaminating the oil.
I then ended up replacing the head gasket and ran the boat with the muffs no issues would reach about half temp.
the starter motor ended failing so the boat sat for about 2 weeks while i waited for a replacement after the new starter was fitted i fired the old girl up and after about 10 minutes it started over heating :mad-new::mad-new:.
I then put a new impeller kit on and now it runs fine pumps plenty of water only reaches half temp and thats after about 30 min at 2000rpm.

Now the problem im having is after i run the motor im losing about 1 litre of coolant basically the exact amount the riser is holding and im contaminating the oil with water again and seems to have a fair amount of steam coming out of the valve cover keep in mind the boat isn't getting hot.
All i can think is either cylinder head is cracked the riser gasket has failed or a faulty shutter?
Has anyone had a similar issue or know a cause any help would be great.
thanks fellas.

 

[Bt Doctur]

Sounds like you have a few issues .an impeller does not go bad sitting for 2 weeks so evidently you had a problem with temp prior to the starter failure
Water in the oil on those motors only can happen from a bad elbow leaking water inbto number 3-4 cylinders.Now if you said AF in the oil then you would suspect a head, head gasket, cracked block, improper gasket, improper assembly.

 

[nathant]

Thanks for the reply, I forgot to mention the overheating was happening prior to replacing the impeller.
it is definitely AF that’s leaking into the oil not the raw water.

 

[Scott Danforth]

Did you use a mercruiser head gasket? If not, get a mercruiser head gasket

Did you do the waterpump speedy sleeve repair on the cam snout. If not, do that update

Have the head surfaced

How is the heat exchanger? Have you had it checked?

 

[kenny nunez]

In reference to what Scott advised the “weep” hole may be plugged up and not letting the AF out to show that the pump seal is not holding. I once saw a 470 that someone plugged the hole with a screw.
If you can get a radiator pressure tester you can pressurize the system and find the leak .

 

[nathant]

I did indeed use a genuine head gasket, I have not done the cam seal yet. As for the weep hole it’s hard to see so have to check that.

 

[Scott Danforth]

all 470's will need the cam seal speedy sleeve. some will be replaced a few times.

 

[stonyloam]

Did you retorque the head after bringing it up to operating temperature the first time?

 

[nathant]

No it hasn’t been re torqued yet it’s only been ran the one, was going to run a few time beforehand, the amount of coolant loss I’m having I’m guessing a cracked head the boats going into the shop for a full overhaul.

 

[Scott Danforth]

dont assume you have a cracked head

check the cam seals first

do a pressure test of the cooling system. on your motor that is extremely easy

 

[DLNorth]

Scott,

are 470's worth repairing, ie, can they be made reliable? or are they better replaced?

Dan

"all 470's will need the cam seal speedy sleeve. some will be replaced a few times."

 

[Scott Danforth]

For the work to put into a 470 to make it reliable, you could have dropped in a 4.3 V6 and have been boating for less money

Just search 470 here on iboats and make your own conclusion

 

[Tassie 1]

Aussie or NZ boat?

 

[Bt Doctur]

Did you use sealant on the head bolts?

 

[DLNorth]

Thanks Scott,
that's pretty much what I thought.
Dan

 

[nathant]

Will give an update on what the issue is once out of the shop.

 

[nathant]

Did you use sealant on the head bolts?

Used a copper based sealer

 

[Bt Doctur]

what type?, head bolt threads need sealant so that fluid cant go up the threads into the valve train

 

[Scott Danforth]

For what its worth....for the bill you will pay to have a shop look at your 470, you could buy a truck load of tools and a 4.3, or you could update your 470 with all the things it needs and have a pile of tools for next time

 

[stonyloam]

The head should be retorqued after the first time it is run up to temp. Pull the plugs and take a look at the insulators. They should be tan in color, if one is snow white it would indicate coolant leaking into that cylinder. The other place you could loose coolant is at the exhaust elbow gasket, but it would not put coolant into the oil. For sure check the engine water pump weep hole. It is on the lower starboard side of the pump. Stick a paper clip or something in to make sure it is clear.