Overheating?

[zbishka]

Hey All,
I need some help. I have an 86 Sportcraft with 170hp. Mericruser with Alpha One Power Trim XD
Last year the boat ran great my only issue was the fuel gauge not working properly this year I'm cruising down Lake Erie and all of a sudden after about 20 mins I am surrounded by a cloud of white smoke with the scent of antifreeze. I immediately shut the engine off, had to be towed into the harbor as I was affraid to start the engine again in fear of doing damage. After the engine cooled, I washed all the antifreeze off of the engine, checked the hoses for holes and nothing. So I put in fresh antifreeze, put the muffs on while water was running through the engine I started it, ran it for about 45 mins, everything seemed to be fine. I took it back out into the lake and within 1/2 hour the same thing happened. I looked and there was antifreeze shooting out from under the Radiator cap. The temperature gauge was at 180 degrees when it started shooting out antifreeze. What is the problem? Thermostat, Worn out Radiator Cap, Impeller? PLEASE advise. Thank you in advance.

 

[Aviator5]

Re: Overheating?

I bet yo it is a blown head gasket. I had the same issue with my 470.

 

[zbishka]

Re: Overheating?

There is no water in the oil. Wouldn't that suggest a blown head gasket?

 

[Don S]

Re: Overheating?

There is no water in the oil. Wouldn't that suggest a blown head gasket?

AF in the oil is not the only way for the head gasket to fail. You may have blown from the cylinder to the water jacket. Easily done on a 470 due to the open deck design of the block. Fill the cooling system (Use just plain water for testing) and start it up again. Leave the cap off and watch for bubbles in the water. There shouldn't be any.

 

[zbishka]

Re: Overheating?

I have a 170 not a 470 does this matter?

 

[Aviator5]

Re: Overheating?

I had exactly the same problem as you've described. Engine would run perfectly on muffs. Won't be any bubbles in the coolant. But once on the lake coolant would be all over the bilge. Then I reved up the motor and could se bubbles coming out, but only at about 2/3 of the throttle and up.
Compression test - great on all 4. Leakdown test - shows no problems.
Only when I pulled the head off it revealed the blown gasket. And there was no oil in the coolant or coolant in the oil.

 

[q5ka]

Re: Overheating?

A 170 is a 3.7L which is the newer 470 motor. It is also known as the 165, 180, and I think there was a 190. It was named that way to try to show the HP. The 470s were all 170 HP (please correct is I am wrong) and the 180/190 had a 4 barrel carb on it. These are basically the same engine except our newer ones came with 4" heat exchanger. Get a leak down test done and see if you blew the gasket. I would say the chances are very high. Not a bad fix for you to do yourself but does take some time and you need the right tools.

 

[zbishka]

Re: Overheating?

Very Interesting about the engine numbers. Thank you ALL very much. PLEASE keep your advise for this problem coming. Does anybody know of a reliable boat engine mechanic here in Buffalo, New York?

 

[Prop Buster]

Re: Overheating?

zbishka,

Reading throught the posts and came across yours. Thought i would offer what I experienced since it was a nuisance for two years and costs me close to $1200.00..... BEFORE I actually resolved the issue of overheating myself with a little investigative work (I thought that what I was paying for in the first place.)

What I found afte everyone checked everything, supposedly, was the stainless steel flaps in the exhaust just pass the manifolds. These stainless steel flaps , as you probably know, prevent sea water from entering the engine. Well, both of them were broken on one side. Sometimes they would open and things seem fine. Other times they would get cocked and wouldn't open, hence the overheating....
After I found these two $35.00 pieces of nightmare, I replaced them and had no problem ever since.

Hopefully you already resolved your overheating issue, if not, please check for these flaps , I have a 95 maxum and I have been told that they usually last no more that 10 years....

Good Luck
Chuck

 

[zbishka]

Re: Overheating?

What could of gone wrong to cause my boat enigine to overheat this season?

Meaning is it something that builds up through out the years, something that someone did or didn't do while winterizing the engine?

I ask ONLY because as I said last year when I bought the boat it ran GREAT except for the fuel guage being off which it still is. Then I take it to someone who owns 2 racing boats (much more expensive than mine), and supposibly winterizes his own engines. He told me he'll winterize it for me while he does his. And now this happens. He says he fogged the engine but what he actually used to do it I have no idea. I asked him and he said boat motor fogger. Is it possible that maybe he missed something while winterizing the engine?

Any help you can give me would be great. Thank you again in advance.

 

[bruceb58]

Re: Overheating?

Your first overheat may have been caused by a bad impeller but now you may also have a blown head gasket because of your overheat.

 

[zbishka]

Overheating

Overheating

Thanks everybody for sharing your knowledge and input. Keep em coming.

It seems as though there are a lot of things that could of caused my engine to over heat this season. But from the majority of replies I'm leaning more towards it's the impeller, head gasket and/or the thermostat. Should I replace ALL of these at one time or just do the process of elimination starting with the thermostat?

Is there a step by step illustration available on how to change the head gasket and impeller?
I do have the SELOC Mercruiser Stern Drives Manual 1964-91. But it isn't very clear and the pictures are black and white resulting in it being very hard to see all (parts) involved. In fact it does have some troubleshooting factors in there but nothing that describes my experience i. e. The white smoke and the antifreeze coming from under the radiator cap.

Is there perhaps a "newer" more clearer version and/or a different manual that will help me?

Thanks a million guys. I'm surprised that there is nobody from Buffalo, New York on this site or is there?

 

[zbishka]

Re: Overheating?

I found out that I melted the impeller and some "tube" is blown which looks to have been caused by age. What tube are they talking about?

Here is my info. for my sterndrive, please let me know if you need more info. in order for me to order the correct replacement parts. I have a 86 Sterndrive Mercruiser 170 hp 4cyl. 2bbl. Mercury Serial# Range 6916779 thru 0B434940. Lower Unit: Alpha One1986 Power TrimXD

Could somebody please direct me to the part numbers for these parts. I was told if I get the parts I can get a decent price on labor for installing them.

Thanks a million guys for all your help.

 

[nola mike]

Re: Overheating?

I found out that I melted the impeller and some "tube" is blown which looks to have been caused by age. What tube are they talking about?

Here is my info. for my sterndrive, please let me know if you need more info. in order for me to order the correct replacement parts. I have a 86 Sterndrive Mercruiser 170 hp 4cyl. 2bbl. Mercury Serial# Range 6916779 thru 0B434940. Lower Unit: Alpha One1986 Power TrimXD

Could somebody please direct me to the part numbers for these parts. I was told if I get the parts I can get a decent price on labor for installing them.

Thanks a million guys for all your help.

the tube is most likely the plastic water jacket guide, which i don't think is strictly necessary but might make getting the drive back together a bit more difficult. i'd get a complete impeller kit including the base. check manual #8 in the adults only section here--very thorough troubleshooting section on overheating in there, including specifically how to test for a blown HG. With an "explosion" of coolant though, seems like you'd need to have combustion gasses in your coolant-->blown HG. if that's the case, you'll need your head checked for warpage before you replace it.

 

[zbishka]

Re: Overheating?

nola mike,
Thank you for your response. You hit the nail right on the head by saying it is the water jacket guide. I really did a great job this time.