1986 Mercruiser 350 5.7 260HP 1 pc seal replaced by 1977 2 piece main seal SB 350

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Seaman
Joined
Jul 16, 2007
Messages
63
I am in the middle of an engine swap from a 1986 Mercruiser 5.7 260 HP 350 small block. to replace with an older late 70's chevy 350 small block which has been converted to marine. My friend that is helping said we need to get a new flywheel, the problem being the fly wheel on the Mercruiser was a one piece rear main seal the older chevy block is a two piece rear main seal. The one that came out of the Mercruiser has 159 teeth and is 14 inches across. My problem is i am trying to figure out the modifications that need to be made and exactly which fly wheel i need and useable conversion fly wheels. in other words I do not know exactly which fly wheel I am looking for. I have seen many on E-bay but there are so many different ones, some for standard and some for automatic. Do I need any other parts besides the fly wheel? Also, when I was putting one of the engine hoist loop I used the wrong bolt on the head and I was not paying attention and I was not turning the bolt that hard bolting the engine hoist loop into manifold on the end bolt closest to flywheel and almost at the top at the back of the motor at the back of the head fly wheel side about an inch and a half down somehow smoke came out of a tiny pin hole and what seemed like gasket material came out which I assumed I put a crack in the head so at that point I grinded down the paint to see the damage done which I did not see any nor a crack but I know its there so I grounded down and put devcon 10110 top of the line appoxy the JB weld equivalent. I was hoping only oil goes throught this part. I am hoping for the best or a temporary solution. I did not want to start sinking more money or tear down the head of something I am not sure of at thispoint. To summarize whats up with the head and what mods need to bemade for the fly wheel situation and what fly do I need. If I can post pictures I will post the flywheel that came out and the back of motor going in




 

proshadetree

Lieutenant Commander
Joined
Jul 19, 2008
Messages
1,887
Re: 1986 Mercruiser 350 5.7 260HP 1 pc seal replaced by 1977 2 piece main seal SB 350

The mercs and omc flywheels Ive seen are for a stick shift.Also the one on my side winder with a 455 is for a stick.They even had holes drilled for a pressure plate.Now I going to catch crap over this because you need to use marine only parts.Ignition and fuel Ill go with and dont even think about a automotive starter.But they all seem to be stickshift.Why do you need a new one.Wont your marine starter fit with the 5.7 flywheel?
 

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Seaman
Joined
Jul 16, 2007
Messages
63
Re: 1986 Mercruiser 350 5.7 260HP 1 pc seal replaced by 1977 2 piece main seal SB 350

I never mentioned anything about a starter the flywheel area and cracking the end of head yes, I have everything from my Mercruiser all going on to the car motor that was rebuilt with marine parts crank cam brass plugs 4 bolt main bla bla bla.
 
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