mercruiser 5.0 swap

[Evil1]

Well heres what I want to do and wanted to get some input on how or what kind of alignment or specialty tools I will need. I own a 1988 20ft Arrow Glass open bow with a mercruiser 5.0 4brrl quadrajet with a Alpha one outdrive. I want to take the motor out this spring and install a 383(chevy 350 stroked w/400 crank) I have here in the garage. I had it in a car and it only has 300 miles on it. It is a very well built motor (Forged crank, H beam rods, forged pistons with 11 to 1 compression. I am gonna install a marine cam with a 462/477 lift, 218/224 duration at .50. I am gonna install 1.6 rockers on it and it has Dart heads with 2.05 intake and 1.6 severe duty manley valves. The block is a 1969 with the thick casting so I am not concerned about the block not bein able to handle the water only cooling. The heads will be way beyond any marine heads out there as in castings. I am not looking for a drag boat but something with plenty of reserve power if I want it. I am running headers with with divertors so I can switch from open exhaust to through the outdrive. Do I need any special alignment tools to put the motor in?? I have had the outdrive off of the boat a few times alrady so that doesnt bother me to remove and install it. I do have a lift to pull the engine and replace it. Anything someone can think of that I might need?? I appreciate any input or help. Thanks in advance. P.s. This is a fresh water boat only.

 

[Bondo]

Re: mercruiser 5.0 swap

What you're proposing is Very Doable......<br />But,<br />You'll need an alignment bar to line up the coupler,+ gimbel bearing...........<br />And,<br />You'll need a Different Coupler..... The motor you're taking out is a 1 piece rear seal......<br />Also,<br />Your Compression is Way Too High.............<br /><br />Good Luck.......<br /><br />BTW, Welcome to iboats forums.............

 

[Evil1]

Re: mercruiser 5.0 swap

what kind of compression ratio should I be looking for? I really dont want to change out the pistons or heads. The motor is a complete running unit. I can get the compression down to around 10.25 if I use thicker head gaskets but that would be about the lowest I could get it.

 

[Bondo]

Re: mercruiser 5.0 swap

You're the man buying the fuel for it..........<br />If you don't mind buying your gas in 55gal. drums, I'm sure it'll be Fine..........<br /><br />At 10.25 you're going to be buying the Highest octane you can find.........<br /><br />9.5 is alot more reasonable for marine duty........<br />Cutting the timing back will help......<br />What kind of rpms are your goal ????? 5 grand is about All that Alpha wants to see.....<br /><br />You Might have the Right Idea...... But, the Wrong Motor.......

 

[Evil1]

Re: mercruiser 5.0 swap

Well the marine cam I was gonna put in it was good from 1300 to 5300 rpms. The motor was an 11 second drag motor that I used for one season and now it is just sitting around doin nothin. The cam that was in it was a 564/ 576 lift and used to run in the 2800 to 7000 rpm range. I was gonna put it in my 69 camaro but went with a big block instead. So My dilemma is I have a $6000 motor collecting dust and wanted to see if it was feasible to put it in my boat. Maybe I should just find a good set of stock heads with a 76cc chamber and rebuild them with some good valves. I know that would drop the compression to about 9.8 then.

 

[Bondo]

Re: mercruiser 5.0 swap

You're going to be putting all this power into an outdrive that's only good for 300hp.......<br /><br />Torque,+ Shock will Kill an Alpha....<br /><br />A set of open chamber heads, with small runners,+ a thicker gasket, will possibly make this an acceptable boat motor.......<br /><br />As you probably know, a SBC is a System that can be built to do Many Different Things.....<br /><br />But, An 11 second Drag Motor doesn't mean it's a Good Boat Motor......<br /><br />Torque moves a Boat.........<br /><br />Raw Horsepower wins at the Drag Races......<br /><br />Whichever way you go......... Good Luck.....