4.3 Merc Cracked Block! Please Help

[df44]

I just bought a 1991 sportcraft that has a 4.3 mercruiser. The boat has 150 hours and I purchased it from the original owner. I thought I got a great deal, start up great and looks amazing. I went to clean it yesterday after about 2 weeks from purchasing it and found the freeze plugs were popped out. I've checked the oil from the dipstick and there seems to be no water but I can't get the oil filter off yet to really check. I called a few boat mechanics and they are all saying it's more than a 90% chance my block is cracked. Does this sound right and if it is, what are my options. I spent all my money on the boat and now I am stuck with a boat I can't afford to fix. Please send me some suggestions...

 

[searay3]

Re: 4.3 Merc Cracked Block! Please Help

It couldn't have run 'no problems' if the plugs were already out. you would have had a lot of water in the bilge. After the test/sale run, if you did not drain the block and live in a cold climate you may have well frozen and broken the block. I live in nebraska and we still have hard freezing at night. Anyway, water under the bridge so to speak. You'll have to start taking it apart to determine what actually is damaged. Sorry to say, but the plugs coming out is not a good sign. You could start by pulling manifolds and intake for inspection, but I have a feeling you'll be looking at a new block at the very least....

 

[searay3]

Re: 4.3 Merc Cracked Block! Please Help

There are a few options for a long block, Jasper, Rapido, etc. A truck/Blazer 4.3 of the same vintage from a junk yard would work if you move all the marine parts over. Brass plugs, alt, starter etc. Manifolds also stay full of water and may have cracked as well. There are manuals in the adults only sticky at the top of the forum. You'll be needing the repair manuals.....

 

[Tail_Gunner]

Re: 4.3 Merc Cracked Block! Please Help

Calm down and put in brass plug's. Run it on muffs for a hour or so and see if you have water in the oil....

 

[danond]

Re: 4.3 Merc Cracked Block! Please Help

What process did you use for winterizing the engine and drive? Do you live in a cold climate? Did it get below freezing since you've purchased it?

 

[lowkee]

Re: 4.3 Merc Cracked Block! Please Help

You may have dodged a big bullet with the block plugs coming out. Put in new brass plugs as Tail Gunner suggested, check the oil for water and fire her up.

If you still get freezing temps, you need to drain the block and wait until warmer temps to try all of this. Having it refreeze will only makes things worse, especially since 'freeze plugs' are not really meant to pop out, and you may not get so lucky next time.

 

[wca_tim]

Re: 4.3 Merc Cracked Block! Please Help

If you can't reach em to put the right ones back in easily, get the rubber ones from NAPA to put in long enough to see if you make milk in the oil... I might also be very wary of the exhaust manifolds... (if they had water in them and cracked...


Good luck!

 

[df44]

Re: 4.3 Merc Cracked Block! Please Help

So I had to lift the motor about 6 inches to get the rubber plugs back in, but after getting them in motor seems to run great and no water in oil. I don't understand how the freeze plugs popped out withough messing anything else up but I got lucky.

 

[IVAZ]

Re: 4.3 Merc Cracked Block! Please Help

Did you pull your outdrive off before lifting the motor? Did you realign your motor after you set it back down?

 

[Howard Sterndrive]

Re: 4.3 Merc Cracked Block! Please Help

rubber plugs

that ain't right
core plugs are brass

 

[180shabah]

Re: 4.3 Merc Cracked Block! Please Help

that ain't right
core plugs are brass

He has another thread and used rubber plugs to seal it for testing.

 

[1997StingRay190]

Re: 4.3 Merc Cracked Block! Please Help

BEWARE!!!

I too bought a boat recently with a Merc 4.3. 1997
It had just 1 brass plug pushed out. I put it back in, ran it for an hour in a tub of H20, 30 minutes on muffs at a later date, and never saw any water in the oil (only looking at dipstick).

I figured all was fine, did a full tune up, brought it to the lake on saturday, ran it for ~15 or 20 minutes, brought it to idle to check on everything, it died. Pulled the engine cover and had that water/oil mix (kinda like a coffee w/cream color mixture coming out of the carb.

Got it home, checked the oil via the dipstick, dipstick looked like it had clean oil, strange I thought. Pumped out the oil and it was all that coffee with cream looking mixture. I've already started to disassemble whatever necessary to pull the engine. Count on needing a block- sorry to hear someone else is in the same boat as me. Good luck.

Sean

 

[180shabah]

Re: 4.3 Merc Cracked Block! Please Help

Pressure testing is a safer first step.

 

[df44]

Re: 4.3 Merc Cracked Block! Please Help

yes rubber plugs, they are aftermarket. and yea i was worried about the diptsick only looking clean so i pulled the oil filter and still no water after being on the water, i think im going to be ok

 

[windsors03cobra]

Re: 4.3 Merc Cracked Block! Please Help

The old crap monster cracked block but ran good boat I bought for peanuts cracked its block real good and popped no plugs, DO I WIN ? DID I WIN ?

LoL seriously 3 plugs popped sounds really bad, when I drained my crankcase (waited till the engine was out of the boat) I think I drained about 3 gallons of clear water before the 2 gallon milkshake oozed out.

Ran my $100 74 chevy nova marine conversion for the first time last Friday, ran great, no problems and didn't have to get out a wrench in the 2 hours I ran it. Hit 40 mph @ WOT on a 40 year old speedo/boat and it was very cold outside, had the lake to ourselves.
Cant wait to hit Michigan.

 

[lowkee]

Re: 4.3 Merc Cracked Block! Please Help

...a 40 year old speedo .. and it was very cold outside .. had the lake to ourselves

I can imagine why!

 

[windsors03cobra]

Re: 4.3 Merc Cracked Block! Please Help

It was 37* but hey the sun was out.