Help please !! 4.3 mercruiser on fire ????

[zapcat]

Hi, could you please give me some advice on a problem i had a while ago with my boat.
1990's 4.3 mercruiser- thought the engine was onfire !!

Cruising at 20 knts 3500rpm engine started to sound strange...growling, temp fine, stoped engine noticed smoke at the back, opened engine cover and was engulfed in a cloud of smoke/steam, left it for a few minutes and noticed that the rubber collar around the right hand exhaust had split/melted, and that the elbow was very very hot, got towed in, stripped exhaust, could not find any trace of the butterfly thingy. elbow was quite rusty but no where near all the way so knocked off most of the rust. and found a couple of narrow channels blocked in the elbow.
How could this happen without the engine temp going higher? and also do you think major damage has been done to the engine?

 

[Don S]

Re: Help please !! 4.3 mercruiser on fire ????

The one side plugged up and stopped the flow of water to the exhaust which burned up the hose. Since the other side was still open, the water would circulate thru the engine and keep it cool.
Sounds like you are in need of new manifolds and risers....

 

[Haut Medoc]

Re: Help please !! 4.3 mercruiser on fire ????

What Don S said.....
& if the temp gauge didn't show over heat, I really doubt that you harmed your engine.......
Welcome to iboats, btw.........

 

[bjcsc]

Re: Help please !! 4.3 mercruiser on fire ????

Wow. You got lucky. 2 years ago I watched a boat burn to the water because of the same thing. Once your risers get scaly on the inside, all that has to happen is a piece (or pieces) get loose and block the flow out of the end of the riser (which is not very wide so as to spray). What happened to you actually causes a significant number of boat fires. The fellow I saw said he opened his engine compartment and his riser was glowing red. A few seconds later, thanks to all the new oxygen, it burst into flames and he threw his anchor and bailed.

BTW, I installed EGT equipment for peace of mind.

 

[zapcat]

Re: Help please !! 4.3 mercruiser on fire ????

Thanks for the help, will hope its just the exhaust

 

[zapcat]

Re: Help please !! 4.3 mercruiser on fire ????

Had a good look today and the only problem is that I still cant find the water shutter, tried reaching down the cowhorn pipe but couldnt feel anything, any idea where they have gone? should i have the boat lifted and pull the leg? thanks in advance

 

[Don S]

Re: Help please !! 4.3 mercruiser on fire ????

They are probably stuck in the drive are or just ahead of it up against the shift shaft. (Hopefully Bondo comes along with his picture) You need to pull the outdrive and check.

 

[Bondo]

Re: Help please !! 4.3 mercruiser on fire ????

Ayuh,.........

I'm sure you mean this 5.0l Alpha 1 Gen.II that the P/O said had No Power...........
I Don't wonder Why,.......

 

[Haut Medoc]

Re: Help please !! 4.3 mercruiser on fire ????

tried reaching down the cowhorn pipe but couldnt feel anything, ....:^
Yikes, that just sounds dirty!
That's the 'Y' pipe that you are referring to for future purposes......
Ya'll must be from the midwest....
Just teasin"!......
You could try a shoving a thin piece of flexible metal down the exhaust just to make sure there is nothing stuck further up.....
But it is probably where Bondo's picture shows it......

 

[zapcat]

Re: Help please !! 4.3 mercruiser on fire ????

Thats great, thanks for the picture. Will have the boat lifted this week and will post the results, in the meantime I will try to keep my posts clean.....

 

[zapcat]

Re: Help please !! 4.3 mercruiser on fire ????

Thanks, found one just as shown in bondo's picture and the other one jammed in behind the prop!

 

[zapcat]

Re: Help please !! 4.3 mercruiser on fire ????

Would this be any good? http://cgi.ebay.co.uk/Mercruiser-St...yZ121901QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Can just print as I need and wont get the pages dirty !!

 

[Lyndy]

Re: Help please !! 4.3 mercruiser on fire ????

Can just print as I need and wont get the pages dirty !!

Given the description on that Item, it is doubtful it is an OEM Manual. I bought one on Ebay here in the United States for my OMC Stringer and it was a copy of a Clymer Manual. The pictures did not transfer well. Very Blurry and Grainy.