1987 mercruiser 4.3 water in motor help!!!

[Kewen300]

Hello everyone,

Been looking for help on here since I started working on my boat. Have been able to peice through different threads but now I'm stuck and decided to open up my own thread for help.

I have a 1987 starcraft 19ft I/O with a Mercruiser 4.3 the motor originally had an overheating issue. Changed impeller and housing. Then took on lake worked fine for a bit then wouldnt start and kept bogging down whenever I would throttle. Got to the spot on lake where we were going turned off and pulled dipstick. Came out as a milkshake. Ended up having to get towed off lake as the boat would not fire up after sitting. Came home took top of motor apart thinking it could be intake gaskets cleaned and changed the gaskets. Put motor back together. Took on lake yesterday. Had a few bugs to workout but motor turned over fine. Check the oil and was a milkshake again. Brought home put in garage for repair. Pulled the #4 spark plug and water poured out. Now I am stuck as to what it could be.

Could the exhaust manifold and riser be leaking and put water into the cylinder and in the oil?

Could it be a intake manifold leak?

Could it be blown head gasket?(wouldnt think it would dump that much water in such a short time)

Could it be crack in block?(still dont think water could get in in that short of time)

Trying to find a solution before I take it down passed the heads.

Thanks in advance everyone look forward to seeing answers.

 

[alldodge]

Pressure test the block

Drain all water from the block

Disconnect hoses going from thermostat housing to exhaust and plug

Disconnect hose coming from the drive to the thermostat housing and install a schrader fitting.

Apply around 15 psi of air pressure and listen to where the air is leaking from

 

[Furbird]

Need to do a compression check and a cylinder leakdown test but my vote is for a blown head gasket. I bought a truck once with a head gasket blown so bad that I drove it from the trailer into the shop and it was already overheating; pulled two spark plugs and water came out of both cylinders. Total run time was less than 2 minutes.

In your case, if it wasn't a blown head gasket, the engine would be hydrolocked or it would have a rod hanging out of the side of it and would sound like a jackhammer pounding steel.

 

[tpenfield]

Could be any of those things you mentioned. If the engine is still together, you can do a cooling system pressure test to see (hear) where the crack/leak is.

As you take the engine apart, start looking for evidence of where water has been in the top end of the engine.

 

[Kewen300]

UPDATE

Thanks to your suggestions I have done some testing. First took out all remaining spark plugs and found the #6 plug was a bit wet and noticed some surface rust. No other plugs looked wet by water.

I capped off all 4 cooling lines, and hooked air to the water inlet line. As soon as I did air came shooting out of the #4 spark plug hole. Little bot of air out of the number 6. The other holes were fine.

So am I correct in I have an extremely blown head gasket?

Should I do both side or just the one side that's blown?

Should I have the heads machined down?

Can someone share a link for a how to do a head gasket on a 1987 mercruiser 4.3?

Thanks for all you help!!!!

 

[alldodge]

So am I correct in I have an extremely blown head gasket?

Agree most likely head gasket

Should I do both side or just the one side that's blown?

You could, but wouldn't be that much more to do both

Should I have the heads machined down?

Only if the head is warped, and then only enough to flatten

Can someone share a link for a how to do a head gasket on a 1987 mercruiser 4.3?

Let the machine shop find you the set you need

 

[Kewen300]

Alldodge.

Thank you. The last question I meant the remove and replace instructions for things like all the bolt and nut torque specs.

New to the forum and getting lost in these how yo sections lol

Thanks for answering my questions

 

[alldodge]

Its in manual 7
http://boatinfo.no/lib/mercruiser/manuals/mercruiser7.html#/140

 

[Lou C]

I did this same job 3 years ago, same cause past overheat. Mine went almost 3 more seasons before o had water in a cyl and the oil. Not a hard job but you will need:
shop manual
Electric impact gun to remove head bolts (easier less likely to break bolts)
thread chaser to clean out cyl head bolt threads
click type torque wrench
small air compressor to clean parts
Fel/Pro gasket set
new head bolts (if originals are very rusted).
The main thing is keep all the parts marked and organized and you must make sure the block deck surface is REALLY CLEAN and flat and level to less than .003”
I suggest taking the heads to a machine shop and get them checked out to make sure they are not cracked. Also to mk sure the cooling passages are not getting eroded because heads can rust through after years of raw water cooling. Mine were cracked from the overheat so I bought a set of reman heads for $550. Turned out well.

 

[Kewen300]

UPDATE!!!!

Took the motor down to the cylinders and did the headgaskets. Put the motor back together and everything where is supposed to be and it appears I have no spark. And possibly no fuel.

So once I got everything back together I cranked the motor over a couple time to get the new oil flowing where is should be. Then I put the spark plugs in and hooked the distributor up.

Turned the motor over again expecting to have if fire this time and check timing. didnt fire at all. Not even a pop. Pulled the number 1 cylinder plug and its completely dry.

I cracked open the gas line at the pump on the block and gas started spilling out so I fuel that far. Took a multimeter to check voltage. At the time of checking after running the bat. Down a bit Bat was at 12v tested with the key in the on position. The green and white wire on the distributor was at 4.2v the red and white was at 11.5 and the purple wire on the coil was at 11.5. Check the grounds at well.and they are all good. This point not sure where I need to be looking or testing. Before test down the thing fired up fine.

Thank you all for the help.

 

[alldodge]

cracked open the gas line at the pump on the block and gas started spilling out so I fuel that far.

What about at the carb?

Pump the throttle and see if gas squirts in the carb

 

[Kewen300]

Update:

So I went back and readjusted the valve using the 3/4 method. I have fuel pumping through the carb. The battery was on charger when I went to test the electrical. Had 12v at battery, 12 volts on the grounds on the carb and on the odd #cylinder exhaust bend, 12v on the distributor bottom. 12v on the coil pack 12v on the distributor and 4v on the distributor(this one seems odd) motor cranks over but will not fire. There is fuel going into at least the #1 cylinder as that's the only plug I pulled to check.

Not even getting a pop from the cylinders. Youd think if the motor was out of time itd at least pop during cranking,

Not sure the next steps in this diagnosis.
Could there still be no spark at the plug even with power to everything else?
It started right up before I did the head gasket replacement.

Looking for ideas help.

Thank you!!!!

 

[Rick Stephens]

Do testing. You can either stick a screwdriver in a plug wire and hold close to a ground to see if you get spark, or buy a $12 spark gap tester that plugs in between wire and plugs.

Do a compression test. Make sure everything is up to norms.

Check that you are getting fuel at the carburetor. Pull the inlet line and stuff in a plastic bottle and crank the motor - does gas shoot out?

Simple stuff first. Need fuel, compression and spark.

 

[Lou C]

Question:
how did you line up the distributor when re-installing?
if it’s out of time you can have the problem you are having....

 

[Kewen300]

Update!!

Rookie mistake was made. I was off on the timing as there are no TDC Mark's left on this motor. So I now have it close need to get timing light and get it dialed in. However I need a bit more help.

So on the tear down and rebuild the adjustments for the forward and reverse cables. So the boat now does not go in reverse. How do you adjust the cables? 1987 starcraft if needed

Thank you all for the help.

 

[alldodge]

Have a look here
http://boatinfo.no/lib/mercruiser/manuals/mercruiser6.html#/32