Rebuilding or replacing Mercruiser 4.3 in 1996 caravelle 1950SE

[Scott06]

Appreciate the bolt tip, I am not one to force things and break them, but I’ll use the strap wrench. Thanks for fault finding tips too, I’ll try them all to be sure before I pull the engine out, but I’m doing my research early on strong evidence.

I myself haven’t confirmed a cracked block through testing, but the seller said it was and apparently a mechanic confirmed this to him. I tend to believe him as the drive is good and newly serviced (new gimbal bearing and all bellows) and the hull is pretty good/title is legitimate, yet he came down to $450... There is water in the oil which I’ve seen today, lends weight to their diagnosis.

Ok if you have water in the oil yes block is likely cracked. Look under the heads in the lifter valley That is the typical crack location.

 

[Scott Danforth]

or the exhaust flappers failed and you took water up the exhaust, which then went into the cylinders

or the exhaust manifolds failed and you took water in the exhaust ports and went into the cylinders

leading cause of cracked block is improper winterization. usually the manifolds are cracked as well.

however most people simply forget to drain the T-stat well on the intake manifold (there is a 5th drain on the 4.3). and that cracks and gets water in the oil. it may just need to be cleaned and a new intake.

need to troubleshoot.

 

[Lou C]

Here's a pic of that extra drain. The Pre-Vortec engines don't have this.
If I remember correctly the one piece exhaust manifolds were used from the start of the Vortec engines in '96 till '99 or so. So if its a freshwater boat it may still have them. The article I read said that Merc did this because the extra cost of the Vortec engines from GM was $50 and they were trying to save money by not having to make the intermediate elbows that connect to the Y pipe after the cast iron elbows. So it was done for cost savings big surprise. OMC also used a similar design from 85-90 or so, I had them on my engine and never had a failure but heard of those who did.

 

[Scottish_joe]

Ok if you have water in the oil yes block is likely cracked. Look under the heads in the lifter valley That is the typical crack location.

Will do. Should have it tested by tomorrow afternoon, thanks again.

 

[bruceb58]

A 96 boat likely doesn't have a Vortec Head and associated intake manifold.

At least on Volvo, they didn't have Vortec until the LK model which was 97. Even then, an LK model may even be in a 98 boat. Mine is a perfect example of that.

 

[Lou C]

Could be, when I looked up a '96 4.3 on a Merc dealer parts website they do show the one piece manifolds, but its true that a '96 boat could have a '95 powertrain. Either way it will be interesting to see what it is and what's wrong.

 

[bruceb58]

Could be, when I looked up a '96 4.3 on a Merc dealer parts website they do show the one piece manifolds, but its true that a '96 boat could have a '95 powertrain. Either way it will be interesting to see what it is and what's wrong.

No idea about the exhaust manifolds.

Vortec engines in GM vehicles came out in 96 but the marine industry didn't get them until the following year.

 

[Scott06]

Here's a pic of that extra drain. The Pre-Vortec engines don't have this.
If I remember correctly the one piece exhaust manifolds were used from the start of the Vortec engines in '96 till '99 or so. So if its a freshwater boat it may still have them. The article I read said that Merc did this because the extra cost of the Vortec engines from GM was $50 and they were trying to save money by not having to make the intermediate elbows that connect to the Y pipe after the cast iron elbows. So it was done for cost savings big surprise. OMC also used a similar design from 85-90 or so, I had them on my engine and never had a failure but heard of those who did.

More likely than $50 cost diff was how many engines a particular boat builder had in inventory . My ‘91 sea ray 170 had a 1990 3.0 with one of the last (by serial number ) alpha gen ones

same happens when I’m came out with the cobra drive they held back sales until builders could sell their inventory of now obsolete stringer drive equipped boats