got me a project...newb need some help..with my engine

ok i got 1983 four winns 20 ft cabin cruiser..im very excited ,,the boat is in absolutley excellent shape..i picked it up last night....ill be posting pics later today...ive got to go back and pick up the motors..it had a 305 mercruiser in it..the guy i got it from was upgrading to a 350...he has the motors on the ground..side by side..the guy that was building the motors had a tragic accident and past..so i got the boat from his family..so i dont know if the block is a marine block or what..the 305 is..its the original motor..it seems he has taken the crank from the 305 and put it in the 350..the 305 is tore apart..only thing left is basically heads and block intact...so i dont know exactly where to start ..im a mechanic and have built a few motors..but not for boats...i know the blocks are origin from a 010 chevy truck block...dont think he replacxed the cam from the 305 or the timing chain..doesnt a boat motor and car motor rotate the opposite direction...boat engines rotate left right???????

so anyways i pick up the motors this weekend...all the parts from the 305 are there..manifolds etc...so i do have the parts i need to exhange to the other block...the 350..has everything almost ready on it marine oil pan from 305..flywheel..but i need to know where i should start....?????should i tear the 350 back down and start over on it just to make sure everything is marine ready or what...freeze plugs ..marine gaskets..etc...i know the boats going to run higher rpms longer than in a car...
just want to do it all right first time round..and not put all my work into changing out the engine again.plzzzzzz.....plzzzzz

ADVICE WILL BE HELPFUL....I KNOW U ALL CAN STEER ME INTO THE RIGHT DIRECTION...EAGER TO GET THE BOAT OUT THIS SEASON...HOPEFULLY...

Re: got me a project...newb need some help..with my engine

how could i determine which directions the 305 mercruiser engines rotation was ....can i look for serial number go that way????????plz help

Re: got me a project...newb need some help..with my engine

dloveb said:

how could i determine which directions the 305 mercruiser engines rotation was ....can i look for serial number go that way????????plz help

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Ayuh,.... The motors are Standard rotation, left-handed, just like every other SBC...

Re: got me a project...newb need some help..with my engine

why was he putting the crank from the 305 into the 350?

both engines are LH as Bond-o pointed out.

your original boat motor was a 2-piece rear seal motor (being a 1983). it could be the prior owner was building a frankenmotor because he found a 1-piece rear seal block and decided to change crank vs finding a different flywheel. however this is just speculation.

what year 350?

Re: got me a project...newb need some help..with my engine

Both engines are standard rotation, but
305 and 350 are different animals, you might want to do some more research on the car forums or at Summit before going that way.
On a cursory search it seems they are balanced different. I do know that a 305 is internally balanced, and a 350 is externally balanced, so the harmonic balancer needs to match the crank you are using. I'd hate to see you do all that work and have her shake herself all over the bilge. Also I would want to be sure of the head gaskets, being marine or not, and make sure the soft plugs are brass for marine use.

Re: got me a project...newb need some help..with my engine

Thanks guys u all are a great help. When I get the motors ill be doing more research. And get back here for more advice thanks million

Re: got me a project...newb need some help..with my engine

You might be miles ahead to take the 350 block and measure it out, take it to machine shop. Then order a completely new rotating assembly, and marine gasket kit. Do it once and do it right. The heads if good can be used from either the 305 or 350; depending on head cc you might have to figure that into piston selection. Building a marine motor is not much different than a auto motor. Just have to do a few specific things.

Re: got me a project...newb need some help..with my engine

Ok now for my out drive its a mercruiser it says 898 powersteering. On it so what type out drive is it. I've seen on here on iboats ..alpha. and bravo. What type is it.

Re: got me a project...newb need some help..with my engine

markheck1 said:

Both engines are standard rotation, but
305 and 350 are different animals, you might want to do some more research on the car forums or at Summit before going that way.
On a cursory search it seems they are balanced different. I do know that a 305 is internally balanced, and a 350 is externally balanced, so the harmonic balancer needs to match the crank you are using. I'd hate to see you do all that work and have her shake herself all over the bilge. Also I would want to be sure of the head gaskets, being marine or not, and make sure the soft plugs are brass for marine use.

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only the 383's and 400 were externally balanced.

Re: got me a project...newb need some help..with my engine

ok so im fine as long as the crank from the 305 is put in the 350 block and the cam right....and of course the marine manifolds.etc....the oil pan is already on the 350...im pretty sure the crank and cam is in the 350...im thinking as long as i change freeze out plugs to bronze..
all head gaskets are stainless whether its for a car or boat..so i dont see sense on worryong bout the gaskets..
im still thinking of putting the heads on the 350 thats on the 305...i do know 305 heads are marine heads plus 305 heads have shorter valve clearance,,so thats going to add extra hp ...

Re: got me a project...newb need some help..with my engine

Re: got me a project...newb need some help..with my engine

Re: got me a project...newb need some help..with my engine

this is the boat its in excellent shape...for what i have in the boat n motors...practially stole the thing ....so its worth playing with...im getting the motors this weekened...so ill get some pics of my motor work that ill be doing...

Re: got me a project...newb need some help..with my engine

dloveb said:

ok so im fine as long as the crank from the 305 is put in the 350 block and the cam right....and of course the marine manifolds.etc....the oil pan is already on the 350...im pretty sure the crank and cam is in the 350...im thinking as long as i change freeze out plugs to bronze..
all head gaskets are stainless whether its for a car or boat..so i dont see sense on worryong bout the gaskets..
im still thinking of putting the heads on the 350 thats on the 305...i do know 305 heads are marine heads plus 305 heads have shorter valve clearance,,so thats going to add extra hp ...

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I wouldnt run it. I would pull the motor apart and build a proper 350.

and do not put 305 heads on the 350. the small combustion chambers raise the compression ratio, and the small valves choke off flow.

Re: got me a project...newb need some help..with my engine

I ve been reading some of the forums on here bout the arguments about boat and car blocks ...god,,, i dunno ..just seems like if its for a boat,,then u should get it for a boat...if its for a car u should get it for a car....but he blocks..for marine boats..has the 010 stamped on it just like truck sbc chevy 010 same stamp..thats the nickel cast right??????so what in the heck is different..other than marine accesories...do they put stainless cranks and cams in the block to make it a marine motor....lol?????so many different opinoins..im seeing and getting...where are some facts..lol
i just want it to be right...if i have to tear down the whole 350..block and redo what that guy has already done...so be it...i guess...lol

Re: got me a project...newb need some help..with my engine

but like i said im new to the boat thing,,,so im taking all the advice being given...to the best of my knowledge...

Re: got me a project...newb need some help..with my engine

Scott Danforth said:

only the 383's and 400 were externally balanced.

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Hmm...ok, man I thought for sure the balancer for my 305 in my truck was completely round, but a 350 wasn't....of course my friend built a 400 too, so maybe that's what I remember.

dloveb said:

ok so im fine as long as the crank from the 305 is put in the 350 block and the cam right....and of course the marine manifolds.etc....the oil pan is already on the 350...im pretty sure the crank and cam is in the 350...im thinking as long as i change freeze out plugs to bronze..
all head gaskets are stainless whether its for a car or boat..so i dont see sense on worryong bout the gaskets..
im still thinking of putting the heads on the 350 thats on the 305...i do know 305 heads are marine heads plus 305 heads have shorter valve clearance,,so thats going to add extra hp ...

Click to expand...

No, marine head gaskets are different.....

Scott Danforth said:

I wouldnt run it. I would pull the motor apart and build a proper 350.

and do not put 305 heads on the 350. the small combustion chambers raise the compression ratio, and the small valves choke off flow.

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I agree with Scott

dloveb said:

I ve been reading some of the forums on here bout the arguments about boat and car blocks ...god,,, i dunno ..just seems like if its for a boat,,then u should get it for a boat...if its for a car u should get it for a car....but he blocks..for marine boats..has the 010 stamped on it just like truck sbc chevy 010 same stamp..thats the nickel cast right??????so what in the heck is different..other than marine accesories...do they put stainless cranks and cams in the block to make it a marine motor....lol?????so many different opinoins..im seeing and getting...where are some facts..lol
i just want it to be right...if i have to tear down the whole 350..block and redo what that guy has already done...so be it...i guess...lol

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that is a pretty nice lookin boat...

Nope, different head gaskets, soft plugs, and external parts, (starter, alternator, fuel pump, cooling, etc...)

Re: got me a project...newb need some help..with my engine

boat blocks, industrial engine blocks and truck blocks come off the same assembly line (same part number) Cranks, heads, etc too. what makes a marine engine a marine engine is the following:

composite or stainless steel head gaskets (depends on year). Use Felpro if your buying. stay away from Mr Gasket
brass core plugs
marine cam (similar to a truck cam, more like an RV cam - overlap and duration specified to prevent reversion)
marine fuel system (J-tubes, vent lines, etc.)
marine exhaust manifolds and risers (water cooled)
marine electrical system (shielded alternator, distributor, and starter)
circulating pump has stainless impeller

there is no special casting alloy for marine engines. They do not use stainless cranks or cams. those items are cast iron

the flywheel in many cases is a truck manual transmission flywheel.

Re: got me a project...newb need some help..with my engine

Ok scott. Im listening. So I should buy gaskets sets. A new cam. The crank is fine that's in the 350 right. I have all the marine parts off the 305 merc.. will it all transfer to the 350. And the heads on the 350. Will they be fine to use if they are not marine heads. Ur right. I want it to all be right ...no redoing things twice.

Re: got me a project...newb need some help..with my engine

Now my distributor off the 305 merc. Will it work on 350. I know the quadrejet carb. Off the 305 will... The 305 camshaft should be a marine cam right. Will it work in the 350. Or should I buy all new ?????