Water entering motor - 4.3L Mercruiser

[Spiderhole]

Hello, at the end of the season I completely winterized my motor, drained everything, block, risers, water pump, etc... Right before I put it away, I determine that water was somehow entering the motor. I was running like crap. Earlier in the season, we had to replace the block with a fresh block because the previous owner had not properly winterized the boat and the block cracked. I could physically see the cracks in the block once the intake manifold was removed. I don't get out on the lake that often, so it was only run twice for short periods all last year. When I replaced the block, I also replaced the manifolds/risers as well because I could see that both sides had cracked. I used the original heads and intake manifold because I could not visibly see any additional cracks. However, something is clearly wrong and for the life of me, I can't identify where this water is coming from. I tore the manifold back off the block and there are no cracks on the top of the motor in the common places where they would crack - and since I had completely drained this block before I stored it over the winter, I really don't believe this block is cracked. I have checked the manifold again, and I don't see any cracks. I also don't see any cracks on the heads. I am wondering if maybe the manifold seal did not properly seal or something else. I am wondering if I need to take the heads off at this point. What else should I check?

 

[Scott Danforth]

describe how you winterized

take the exhaust manifolds and pressure test them, or if you have the elbows off, use the acetone test.

99.99% of the time when the block gets cracked from improper winterization, the heads, intake and exhaust maifolds are junk as well

take the heads and have them pressure tested
take the intake manifold and check the bottom of the thermostat housing
do you have the correct intake gasket
did water sit in the engine all winter, because if so, you have other issues.

 

[Spiderhole]

To drain I pulled the hoses off of the water pump and thermostat housing. I pulled the drain plugs from both sides of the block and made sure they were free of debris and water fully rushed out of both side. I removed the all the plugs from both sides of the exhaust manifolds and drained everything out of them. Like I said, what water in the oil after we replaced the block last season before I put it away. I didn't have time to try and make these repairs until now. The exhaust manifolds, elbows, and block were all brand new which makes my believe the intake manifold, and or the heads are the problem. I live in Dallas, TX. This is a 1986 4 Winns. What would you say is the correct gasket for the intake?

 

[Scott Danforth]

Sounds like a proper winterization

The water in oil over winter may be a problem

Because the intake gaskets are specific to intake design. It is easy to use an automotive gasket, however it would leak around the water passages

 

[Bondo]

I have checked the manifold again, and I don't see any cracks. I also don't see any cracks on the heads.

Ayuh,...... You should be able to visually inspect the manifold,.....

But the heads should go to a machine shop, 'n be magna-fluxed,...

They can, 'n do crack in the intake, 'n exhaust ports,.... not easily seen,.....

 

[Spiderhole]

I will throw myself under the bus and say that I believe we used automotive gaskets on the intake... they are Felpro. However, I don't know how to confirm if in fact there was a leak there based on that fact alone. Although the intake manifold is not the prettiest thing I've ever see inside the thermostat area, I don't see anything at all that indicates any cracks. I have checked it all over with a flashlight and anywhere else - I just check it again on my work bench. At this point, I am thinking either heads, or gasket...

 

[Spiderhole]

Can anyone here tell me what the correct gaskets for my intake are for marine application? The is a 1986 two barrel intake. I see the ones for 96 and newer.

I think my plan of attack is to pull the heads and have them tested.

 

[Scott Danforth]

Heads are as follows:
1985 with perimeter bolts
1986-1995 with center bolts
1996 and newer vortec

intake manifold changed with the balance shaft motors in 1992 as well


You need a felpro marine for the 1985-1991 motors if yours is a 1986. Make sure the gasket matches the ports

You still should get your heads checked. If bad, suggest vortec heads and new intake

 

[Spiderhole]

Two questions...

where can I order the gaskets?

second question, if I do go to vortec heads and intake, will I need to change the distributor and the carb? I’m running a two barrel, I bet those vortec heads need more fuel supplied to them than the two barrel delivers.

 

[achris]

...second question, if I do go to vortec heads and intake, will I need to change the distributor and the carb? I’m running a two barrel, I bet those vortec heads need more fuel supplied to them than the two barrel delivers.

Nope, only the intake changes for the Vortecs. And it'll be quite happy with a 2 bbl... But if you're going to change the intake anyway, a 4bbl intake is much easier to find than a 2bbl, so just change the carb (to an Edlebrock 1409) at the same time. Go from 175hp to about 225hp...

Distributor remains the same.

Chris.....

 

[Spiderhole]

Nope, only the intake changes for the Vortecs. And it'll be quite happy with a 2 bbl... But if you're going to change the intake anyway, a 4bbl intake is much easier to find than a 2bbl, so just change the carb (to an Edlebrock 1409) at the same time. Go from 175hp to about 225hp...

Distributor remains the same.

Chris.....

Are the intake, heads, and carb all marine specific?

 

[nola mike]

The heads are not, carb is, and not sure if the intake is marine specific, but don't think that there was an auto application that used a carb + vortec.

 

[Lou C]

If the block cracked the likelihood of the heads and intake cracking are pretty high, I have seen the heads crack right behind the exhaust manfolds where that square plug is. The intake if cracked you should be able to see it if you turn it over and look on the underside of where the thermostat fits. A crack or rotted out area there, would put water right into the cam valley and right into the motor oil.
My old heads were cracked not from freeze damage but from a previous overheat, I had them checked out by a machine shop.
I was able to get a set of re-man 4.3 heads (non-vortec) for about $275 each, my old intake was still good although I bought a spare off of ebay because the non-vortec 4bbl ones are not that easy to find. And for sure use Fel Pro marine gaskets.

 

[achris]

The heads are not, carb is, and not sure if the intake is marine specific, but don't think that there was an auto application that used a carb + vortec.

The only thing 'marine' about an intake manifold is if it's aluminium, it needs to have brass sleeves through the water passages. If it's cast iron, no problems. Carbs are DEFINITELY different between marine and automotive, as are distributors, fuel pumps, alternators and starters, relays and solenoids, and even the humble fuse is different between marine and automotive.

Chris......

 

[Lou C]

Yes Chris I do recall that fuse discussion we had. Open=not spark protected closed=spark protected. Found that on the Buss Fuse website.

 

[Spiderhole]

Cool. I am headed out of town on Thursday to Hawaii for a few days, but when I get back next week I am going to tackle this. If I am going to go as far as ripping these heads off, I am definitely going to go with Vortec heads, four barrel cast iron intake, and marine four barrel carb... and of course the marine gaskets. All my other parts are marine including the distributor and all the other stuff mentioned. I bet what I find when I pull those heads off is that they are cracked somewhere that I can only see when they are off. I assume also that once I do get everything reinstalled that I will need to put the motor to top dead center to install the distributor and eventually time it.

Any advice once I get to the point of changing the oil how to flush out the remainder of this crap that's in the motor out?

 

[nola mike]

The only thing 'marine' about an intake manifold is if it's aluminium, it needs to have brass sleeves through the water passages. If it's cast iron, no problems. Carbs are DEFINITELY different between marine and automotive, as are distributors, fuel pumps, alternators and starters, relays and solenoids, and even the humble fuse is different between marine and automotive.

Chris......

But there is no automotive intake made for this application (carb'd vortec), correct?

 

[Lou C]

I'm not sure who cast them but for sure there are marine 4bbl cast iron intakes for the Vortec marine V6s. I don't believe that the Vortec as used in vehicles ever used a carb, but the Pre-Vortec engines in the Chevy vans did use the Quadrajet before they were discontinued.

https://www.michiganmotorz.com/mercruiser-vortec-intake-manifold-1996-current-p-4368.html

https://www.michiganmotorz.com/volvo-penta-vortec-intake-manifold-1996-current-p-8224.html

same thing same price.

 

[Lou C]

What I did to get the water out...from when I had 2 blown head gaskets.....
ran it, changed oil, drained all water out. repeated this 3x, each time draining the block/heads and manifolds. Its a pain but its what you have to do.

 

[Bondo]

I'm not sure who cast them but for sure there are marine 4bbl cast iron intakes for the Vortec marine V6s.

Ayuh,...... Probably the same foundry that casts 'em for Mercruiser,.......

I know Michigan Motors carries 'em,.....