Where to start? Mercruiser 470 with water in the oil

[Spivy30]

I'm sorry everyone im sure you see this a lot, but I did try and do my research. Anyways heres the back story...I went out looking for a trailer for one of my boat projects and I found this really nice two year old Shoreland'r but it still had the boat and the motor had "issues" which is no big deal I though I would just part out/junk the boat. Long story short the boat ends up being an extremely clean 84' Sea Sprite with a 170HP Mercruiser and I just dont have the heart to junk it. SO here I am with another project...Mechanically i'm not worried about working on the motor I do it everyday with other boats but Ive never seen or touched one of these 470's. I know very little about except about their basic design and known problems. The motor runs "good" but it's getting water in the oil somewhere. Where do I start? Head gasket? Exhaust manifold gasket? Cracked head? Thank you for any help I want to learn as much as I can about these.

 

[Eric 3.7LX Alpha 1]

Re: Where to start? Mercruiser 470 with water in the oil

Welcome to the step child club.

What do you have for compression numbers?

 

[Spivy30]

Re: Where to start? Mercruiser 470 with water in the oil

I think i'm glad to be part of the club but we'll see how things go...I started the boat again briefly today it started easily and idled smooth I noticed I am getting exhaust up into the valve cover and into the vent/breather that goes to to the carb, alot more then would seem normal...I then took the valve cover off to see if there were noticable cracks. The exhaust was coming up by the lifters so i'm starting to think it has a bad head gasket.

 

[Spivy30]

Re: Where to start? Mercruiser 470 with water in the oil

In the picture of the head I put arrows where the exhaust was coming up.

 

[wifisher]

Re: Where to start? Mercruiser 470 with water in the oil

Blowby will send exhaust gas past the pushrods like that. I think you need a compression test, and probably follow that with a cyl. leakdown test.

 

[Spivy30]

Re: Where to start? Mercruiser 470 with water in the oil

Compression was 155 153 156 154

 

[stonyloam]

Re: Where to start? Mercruiser 470 with water in the oil

The two basic tests for a 470 are the compression check (already done and looks fine), and a coolant system pressure check (borrow the tools from Autozone). Is there antifreeze in the engine? Can you smell antifreeze in the oil. Check the waterpump on the front of the engine. There is a small weep hole in the lower port side of the pump housing. Make sure that the hole is open and not clogged. With the engine running look to see if coolant is coming from the weep hole. If the hole is plugged it is possible for coolant to leak past the seals into the crankcase. Are you sure it is exhaust coming out and not just steam? Good luck.

 

[Spivy30]

Re: Where to start? Mercruiser 470 with water in the oil

There is coolant in the engine and the oil is like a milk shake now. What is coming up by the push rods smells like exhaust with burnt coolant. I'm going to check the water pump, if the weep hole is plugged what do I need to do? I'm going to do a leak down test and see whats going.

 

[badkins50]

Re: Where to start? Mercruiser 470 with water in the oil

I think you may need to read this:
http://www.sterndrives.com/470information/470coolantleakrepair.html
Good luck.

 

[Eric 3.7LX Alpha 1]

Re: Where to start? Mercruiser 470 with water in the oil

It is possible that the weep hole was blocked and the cam seals went south. There is also a small allen plug next to the weep hole I think, it's a drain for the coolant and can help clear up any sludge in that area of the weep hole.

 

[stonyloam]

Re: Where to start? Mercruiser 470 with water in the oil

Sounds almost like a head problem, except those compression numbers were so good. Ya got me. Please keep us up to date on your progress. That is not a bad engine if you can get it running, lots of power and easy on the gas. Good luck.

 

[Spivy30]

Re: Where to start? Mercruiser 470 with water in the oil

Thank you for that link...I learned a lot, i'm also going to recheck my compression numbers maybe I didnt reset my tester. I will let you know what happenes. I did go ahead and order a head gasket set.

 

[salty3rd]

Re: Where to start? Mercruiser 470 with water in the oil

If you are still stuck check the exhaust riser/coolant resovoir. If it is bad or the mounting gasket is bad water could get into the oil.

 

[Spivy30]

Re: Where to start? Mercruiser 470 with water in the oil

I rechecked the compression...70lb,90lbs,155,152

 

[Spivy30]

Re: Where to start? Mercruiser 470 with water in the oil

Well I tore it down and everything looks good inside the motor no scoring or anything. I noticed a oil water mix around the bottom of the head when I pulled the intake manifold so i'm praying that its just the head gasket otherwise I did a lot of work for nothing.On the other hand sometimes its fun to tear down a new motor and learn something.

 

[stonyloam]

Re: Where to start? Mercruiser 470 with water in the oil

Great. Do you have the manual? The head torquing, and retorquing sequence is very important, and make sure that you keep the pushrods in the same order they came out. The book calls for perfect seal on the threads, NAPA (permatex) aviation sealant is a good substitute. Have fun.

 

[Spivy30]

Re: Where to start? Mercruiser 470 with water in the oil

I dont have the manual I was looking for something online with the torque specs. I'm going to get going on the motor today

 

[stonyloam]

Re: Where to start? Mercruiser 470 with water in the oil

I dont have the manual I was looking for something online with the torque specs. I'm going to get going on the motor today

Someone hers should be able to give you a link to the manual.

 

[Eric 3.7LX Alpha 1]

Re: Where to start? Mercruiser 470 with water in the oil

You should need Manual# 3 for your '84, however I don't have the link to it. It covers the engine and drive in it.

 

[stonyloam]

Re: Where to start? Mercruiser 470 with water in the oil

You should need Manual# 3 for your '84, however I don't have the link to it. It covers the engine and drive in it.

Hay Eric, I think they made the change in 83, so #8 should be OK, anyway I think the head gasket should be the same in either case, unfortunately I don't have the link for #8 handy.

OK found it for #8 http://www.4shared.com/account/document/zTbCbkDD/Service_Manual_08.html