82' Mercrusier 470 cracked block replacement

[JAMN' Mantis]

Hello
I have a Mercrusier 470 with rust in the # 4 cylinder and am doing a tear down to replace the cracked block .
I found the part and have the time to put in .
However I am having trouble removing the cam sprocket . Is there a pin that hold it from moving ?
How can I remove the timing chain without rotating the engine ( because it is rusted closed #4 )

 

[Bt Doctur]

you remove the 3 bolts that hold the cam sprocket on , then remove sprocket and chain as a unit

 

[Mercruiser420]

Probably rust holding it on the cam

 

[JAMN' Mantis]

Thanks for the info . I still need to remove the impella shaft before the cam sproket ? I read that it was a oposite thead bolt so I turned to the right and broke off the tapered edgeany ideas how to remove impella shaft so i can remove timing chain

 

[Mercruiser420]

So you removed the coolant impeller cover
Removed the impeller (reverse thread)
Removed the timing cover and exposed the timing assembly
Removed the tensioner/guide
Removed the 3 bolts holding the cam sprocket on
Slide out as an assembly

You don't need to remove the stud that screws into the camshaft to remove the sprocket if that's what you mean by "impella shaft".

 

[JAMN' Mantis]

Thank you
I do have the timing assembly exposed . Yes that is what I mean by Impeller shaft .
I will try and remove as a unit tonight and keep moving forward
Thanks

 

[JAMN' Mantis]

Funny Thing .I did try and slide off the Cam sprocket but it will not move . the Crank shaft sprocket will slide together ,but the Cam sprocket is being held on by what looks like a pin . I don't know what it is , But I remember reading something about a " Willcott" pin or something used to secure pulleys .I cannot find anything in the Manual about this or seen one before , not that I have a lot of experience because I don't have any . Can this be something like that .
Does anyone know what this is . I will post a picture soon as I figure out how to do it
Thanks

 

[Mercruiser420]

The pin is to line up the sprocket correctly to the cam so you can bolt it to the cam in the correct position and line up the timing marks correctly, it doesn't hold anything. Often times the cam sprocket will fit a little tight on the camshaft, so gently and steadily pry it off the cam (2 small prybars from opposite sides does the trick) and don't warp anything good luck

 

[JAMN' Mantis]

I will try that . Thank you very much

 

[JAMN' Mantis]

Thanks to all That helped I was successful in getting the sprocket off doing what you had said .I came off rather easy. I guess I was overthinking the problem
I am now on my way to start the rebuild
I will post other questions on a new Post
Thanks again

 

[JAMN' Mantis]

Mercruiser 470 rebuild

I have a Mercruiser 470 Block that I am replacing .
Do I really need to have it Bored and honed ?
What does that mean ?
What about the pistons ? I saved two and need two more
Do I need to have them machined as well ?

 

[Bondo]

Ayuh,..... Welcome Aboard,.... Don't keep startin' new threads, 'bout the Same issue,....

Rebuildin' a motor, starts with Meassurin' everything to be sure it's all within' spec,....

Rebuildin' a motor ain't just throwin' parts together,....
'n rebuildin' a 470 probably ain't the best motor to learn on, as it's a beast all to itself,....

Anyways, keep it all in this thread, so the Info is all together,.....

 

[Mercruiser420]

Did you mention the block being cracked?

 

[JAMN' Mantis]

I have replacement Block that I am starting with
I am buying new Pistons in a couple of days
I just want to know if the block needs to be taken to a Machine shop. The block is in good condition

 

[Mercruiser420]

I would take the block to the machine shop, they'll measure the bores and tell you what exactly you need for pistons/rings. Also they'll pressure test it unless your 100% confident that its not cracked anywhere. You also want to measure the crankshaft journals to know what size bearings you need (cut + oversize bearings or stay standard) and I'd get it polished for the new bearings. Good luck

 

[Scott Danforth]

The easiest, and cheapest way to rebuild a 470 is to replace it with a 4.3 liter and a new alpha drive. Yes you do have to machine a block and hone it prior to new pistons

 

[harleyman1975]

And the pistons are matched to the finished block so let the machinist tell you what size pistons to order so you get them right the first time.

 

[JAMN' Mantis]

Hello again ,The machine shop has the block and it checks out .They will bore it out to what she said was 1 or 2 . I found used pistons online so I can save money .
they are from the right boat but wrong year . Does the piston rods change from years to years ? let me know if anyone has the answer
Thanks

 

[Bt Doctur]

I believe the pistons are a Ford 460 item, I`m a bit hazy on the rods but i think they were from the 302 motors and in my old yellow notes it took a Maverick flywheel

 

[Mercruiser420]

Connecting rods are the same from 1976 to 1989. Do communicate with your machinist though. Let them know what it is exactly yourh trying to do so you don't buy and install wrong parts. For example if your getting the engine bored .020 and installing used standard pistons that's not going to work, you'll need .020 oversize pistons and rings. You can find cheap rebuild kits online. What's wrong with your original connecting rods?