5.0 Mercruiser Vs. 5.0 Chevy motor

[bikerboater]

Hi all, I'm new here. I have a 1986 19' Celebrity Cuddy. Bought it used in 89. Long boring story on everything I experimented with but as of now I have a 406 SB chevy in it. Granted it was custom built(actually the second one, I still have the first one for a spare) It has the 5.7 rods, TRW forged pistons that have the crowns machined to get the comp down to 9.5, Dart heads, Comp Cam 270 Magnum, Victor Jr intake and a very nice working Q-jet carb. I'm running an Alpha 1 SS drive with a 23 LazerII prop. I've had it GPSed at 69mph so it's not the fastest thing around. It is fun to supprise some bass boats with a family type cuddy though!
I did have probems with the original Alpha1 drive. Someone had stolen the orig and the dealer I got the boat from installed one built in their shop. It knocked the lower unit gears out after 50hrs. I had that one rebuilt by another person and it too lasted about 50hrs. The mechanic blamed it on the engine being too big. That is when I bought the SS drive new. I talked to someone at Merc and they said it sounded like bad shimming. He also said the Alpha 1 is one of the most hotrodded drives out there. Remember, this was many years ago. I bought the shimming tools and reconstructed the blown drive. Sure enough, the lower gears were .015 too tight. Evedently, the first guy didn't know what he was doing and the second just reinstalled the shims without checking. I've been running this combination since the early 90s and it's been fine. The cam is mild enough with the 406 that it idles down fine for shifting.

[bocco]

So I never got the clear answer out of all of this. Does GM assemble the long blocks to Mercruiser specs? Or does Mercruiser buy individual components such as cranks, pistons and blocks and assemble them themselves.
I'm assuming that the electrical and fuel systems are all Mercruiser.

[jmherbert]

So I never got the clear answer out of all of this. Does GM assemble the long blocks to Mercruiser specs? Or does Mercruiser buy individual components such as cranks, pistons and blocks and assemble them themselves.
I'm assuming that the electrical and fuel systems are all Mercruiser.
GM assembles the motors (longblocks). I believe that the entire engine is assembled by GM, including the accessories.
Volvo and Merc longblocks are identical, they just have different dressings such as manifolds, ECU's, etc.
The marine motors do have different internals than the other motors.