Cracked 305 Block Issue - Ready For Rebuild

I just stumbled onto this site, and already got some good advice. Natch, there are a bunch of threads on cracked blocks.<br /><br />Ten years ago, I bought a boat with a Mercruiser 260 that had a busted block. Got a used block and did the rebuild myself. Turned out well and got several years' running before selling the boat.<br /><br />A family member bought a 21 foot somethingorother with a Mercruiser 228(?). Unfortunately, being new boat owners, they didn't layup quickly enough and now have a cracked block. Forget epoxy or drillouts using pipe plugs. The area under the intake is bad and allowed water into the oil pan.<br /><br />I think it will be a straightforward repair. I'm planning to get a used block and transfer the guts and bolt-ons, keeping everything stock (and marine, of course).<br /><br />So, my questions: any gotchas on this repair? Any suggestions for 'while you're in there'? Any known problems that can/should be fixed at this time?<br /><br />JPR - Milwaukee

Re: Cracked 305 Block Issue - Ready For Rebuild

Three things. First- The block would be off to the machine shop for the block to be dipped and have the decks and cylinders honed. Second - Master rebuild kit from www.northernautoparts.com Third - Would be to have everything balanced (a must). A hundred bucks or so will add about 30% to the longevity of the motor.

Re: Cracked 305 Block Issue - Ready For Rebuild

Just a thought -- I'm told the 350 is a drop-in replacement for the 305. I have a 305 myself in a '77 Chris Craft, but have been told by a couple of sources that a 350 would give me a whole lot more power. So far, I haven't had the need. As long as the old original keeps running, I'll stick with it. But if you are into replacing the block anyway, maybe it would be worth considering the 350.

Re: Cracked 305 Block Issue - Ready For Rebuild

What oldboat1 says (change to a 350) is where I would have started.

Re: Cracked 305 Block Issue - Ready For Rebuild

JPR, the 228 is the advertised horse power rating for the merc 305. the 350 is rated at 260. so you get a 32 horse power increase with the 350. just be sure the block you rebuild is from the same engine run as your original so all the bolt ons fit. when I re did mine, I made sure the dip stick was on the same side as the original block. one of the folks on this sight mentioned that when they changed the design they also changed the dip stick location, so if you stick to that you should be OK'.........good luck......... If CDV sees this post he will have a lot of input for you

Re: Cracked 305 Block Issue - Ready For Rebuild

I've done a few of these and flashback is correct. Everything will bolt up to the 350 block and you will gain 30 or so free horsepower. The year range is critical...also stay with the same main bolt pattern and make sure the location of the dipstick is the same...also starter bolt pattern. You can save yourself a lot of trouble and money by just making sure the replacement block is the same year as the old one.<br /><br />While we are up...ask to see the rebuild specs before you buy. Some rebuilders have more than one grade of engine. In the lower grades you will find mismatched pistons, cranks that have been ground down too much etc., compare the specs.