Engine compatibility

[rdwyer]

Hi all. I need to replace the port engine in my boat. It's a 1997 merc 5.7L 2 barrel with flat tappets, thunderbolt V ignition and it's pre-vortec

I found a drop in that if compression checks out I'd likely buy to replace it. The drop in is a used 1995 MerCruiser 5.7L with 2 barrel carb. Don't know the ignition system yet or the tappet type, but assuming they were a match, is this the same config?...are the parts interchangeable?...example would the heads of the 97 fit the 95 and vice versa?

Thanks

-Rick

 

[alk]

You sure the 97 is pre-vortec ? I thought that was the year they switched over? What is the 3 digit casting number of the block? 880 or 638 ? If both motors are pre-vortex ( 638) , they are identical, so no issues.

If you 97 is vortec ( 880) and you are replacing it with a complete pre - vortec, all accessories will swap over. I did the same research last year - only possible incompatibility I heard of was perhaps the water circulatiing pump. I assume because you are testing the compression that the heads and intake are coming with the 95 motor you are looking at?

 

[jtybt15]

I'm pretty sure the vortec first came on '98 but could be wrong. Easiest way to check is intake
manifold bolt pattern. Vortec has 2 bolts in each corner. Pre-vortec has 2 in the middle and one at each corner. Either way, it a straight drop-in. No real problem in power differences. If any difference you can feel, adjust with throttle.

 

[rdwyer]

Thanks all.
With regard to the Vortec year, 1997 was the first year introduced but many 97’ boats like mine offered different power packages that year so they had combos of 2bbl and 4bbl pre vortec and 2bbl and 4bbl vortec (they also had a diesel option that year for this boat believe it or not).

I’ve got two remans coming, 5.7l vortec with intake manifold and electric pump coming in. I’ll swap everything else over.

To make a long story short, both engines are bad after the antifreeze was not drained prior to the marina pulling them and storing them for 4 years. During removal they had to of been tipped in a manner that let antifreeze leak into some of the cylinders. They stored both indoors but one slumped to one side as I remeber seeing them. Took the head off and you can see oblong rust stain on two cylinder where they filled with AF. The other engine I worked this weekend. Tested all 8 cylinders...first 1-7 were all between 170 to 180. The last cylinder I test was 140. Oiled it and it shot back up telling me it’s the rings.

So, not looking to make waves but I will mention to the marina that during the pull, when they saw I had AF in they could have called me to let me know that they should have been drained prior to hauling. Expensive lesson learned. Getting excited to be back on the water this.

—Rick

 

[LouC]

Filling with antifreeze should not have caused antifreeze to leak into a cyl. I've been doing it for years and never had that problem. I bet you ad a bad manifold to elbow gasket, head gasket or even an intake gasket that allowed AF into a cyl. If they had not filled with AF you would have had the problem after the boat was re-commissioned but it would have been water instead of AF.