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1999 Malibu Sunsetter engine swap


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Good morning all,

Sorry I am very new to Forums so I’ll do my best.  We tore our crankshaft in half on our Monsoon 320 last year from what I assume was caused the year before from hydrolocking it due to a leaking intake gasket. Long story short, after buying to remans and building them up only to have then blow we were told most likely a computer issue problem and so forth. 

We decided we liked the boat too much to get rid of it so we spent the $$ on a drop in engine from Michigan Motorz.  Brand new GM 5.7, MEFI5, everything included.  Yesterday we put the transmission on and lowered the engine into the hull only to discover that the oil pan drain hits the bottom of the boat with at least 1 1/2” to go. My first thought was that obviously the old oil pan was a low profile one or something.  We measured, and it’s literally identical. Within a 1/4”.  Then I thought possibly the mounts are different but looking at the alignment of it, the engine HAS to go down at least 1 1/2” to fit.  Surely the block isn’t different?  I find it weird that it needs to go down that much, doesn’t fit, and yet the oil pans are identical. 

Many ideas or help?

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Thanks for the reply


Yes!  That’s in my opinion the weird thing. The pans are exactly the same measurement. As you said 8 1/2”.  Just shy of that.  The plugs are in the same spot.  The new plug is slightly bigger because it’s the type that has the dipstick tube mounted to it but it’s less than an 1/8” different in total height. 


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I would check the engine & trans mounts to make sure they are as removed.  You could run a string at the prop shaft angle to verify the crank centerline is as removed with the new engine going in.  Without any support the prop shaft will sag a bit in the packing area so you might need to make sure it is centered in it to confirm.

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