Mercruiser Engine interchange - GM 305 V8
 

Hello, I have a 1985 Welcraft 19’ with a chev 305 V8, the engine has
a cracked block, Water is getting into the combustion chamber and in
the oil, It’s shot!@!
I was told that this motor had been changed once before and that a
automotive 305 was installed, Is this true?, Can I take an automotive
chev 305 and install it in this boat? Anyone know what years will
fit?, I realize that the cams are different and will deal with that.
Thanks.

dave :?:

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Mercruiser Engine interchange - GM 305 V8
 

"dave" wrote in message
news:379785_c336fb55823e9ef8c29f92cb33696008@boati ngforumz.com...
Hello, I have a 1985 Welcraft 19’ with a chev 305 V8, the engine has
a cracked block, Water is getting into the combustion chamber and in
the oil, It’s shot!@!
I was told that this motor had been changed once before and that a
automotive 305 was installed, Is this true?, Can I take an automotive
chev 305 and install it in this boat? Anyone know what years will
fit?, I realize that the cams are different and will deal with that.
Thanks.

dave :?:

--
Posted at author's request, using moderated http://www.BoatingForumz.com
interface
Thread archive:
http://www.BoatingForumz.com/Mercrui...pict99526.html

You pretty much want to start with truck short block and move everything
from your old engine to it. Change out the casting plugs and use new marine
gaskets. Any block up to 1986 should work.

Mercruiser Engine interchange - GM 305 V8
 

On Mon, 2 Jun 2008 13:01:10 -0400, "Jim" wrote:

You pretty much want to start with truck short block and move everything
from your old engine to it. Change out the casting plugs and use new marine
gaskets. Any block up to 1986 should work.

Don't you need a different cam? Or is the one for trucks close enough.

Casady

Mercruiser Engine interchange - GM 305 V8
 

"Richard Casady" wrote in message
...
On Mon, 2 Jun 2008 13:01:10 -0400, "Jim" wrote:

You pretty much want to start with truck short block and move everything
from your old engine to it. Change out the casting plugs and use new
marine
gaskets. Any block up to 1986 should work.

Don't you need a different cam? Or is the one for trucks close enough.

Casady

I'm pretty sure it's what's in the marinized block.

Mercruiser Engine interchange - GM 305 V8
 

"Richard Casady" wrote in message
...
On Mon, 2 Jun 2008 13:01:10 -0400, "Jim" wrote:

You pretty much want to start with truck short block and move everything
from your old engine to it. Change out the casting plugs and use new
marine
gaskets. Any block up to 1986 should work.

Don't you need a different cam? Or is the one for trucks close enough.

Casady

I'm pretty sure it's what's in the marinized block.

Mercruiser Engine interchange - GM 305 V8
 

On Mon, 2 Jun 2008 15:03:33 -0400, "Jim" wrote:


"Richard Casady" wrote in message
.. .
On Mon, 2 Jun 2008 13:01:10 -0400, "Jim" wrote:

You pretty much want to start with truck short block and move everything
from your old engine to it. Change out the casting plugs and use new
marine
gaskets. Any block up to 1986 should work.

Don't you need a different cam? Or is the one for trucks close enough.

Casady

I'm pretty sure it's what's in the marinized block.

So the old one had a truck cam as well?

Casady

Mercruiser Engine interchange - GM 305 V8
 

On Jun 2, 3:03*pm, "Jim" wrote:
"Richard Casady" wrote in message

...

On Mon, 2 Jun 2008 13:01:10 -0400, "Jim" wrote:

You pretty much want to start with *truck short block and move everything
from your old engine to it. Change out the casting *plugs and use new
marine
gaskets. Any block up to 1986 should work.

Don't you need a different cam? Or is the one for trucks close enough.

Casady

I'm pretty sure it's what's in the marinized block.

Double check to make sure you have the correct block as they did
change some in mid 80s. One thing to look at is the angle of the
intake bolts. In early years all the intake bolts were the same
angle. Later on, the inside two bolts changed angles to tilt slightly
more upward. Another change to look at is the rear seal. The engine
went from a two piece rear seal to a special aluminum housing with a
one piece rear seal. When this changed the bolt pattern on the end of
the crank changed as well.

Just about any of the small blocks pre or post 86 will bolt in place
of the engine you have. If the rear seal is not the same then you
will have to get a different coupler. I'd suggest looking for the 350
if you can instead of the 305 as the two are identical except for
displacement. The truck and marine engines also used heavier block
castings.

You must replace the freeze plugs with brass ones.

The cam for marine is different but it is not critical to change.
Truck engines will have a closer cam than cars. The marine cam has
slightly less overlap for improved low end and reduced backflow at
idle while still having a good bit of lift. The most common small
block marine cam has .450 lift.

You will probably want to keep your intake if it is a cast iron 4
barrel one. (Those are actually popular with some stock car
enthusasts in classes where aftermarket alluminum ones are not
allowed.) If not then this is also an opportunity to switch to a 4
barrel carb. It is ok to use after market aluminum intakes.

Most of the marine engines used the larger sodium filled exhaust
valves. These are also found in some truck engines. Depending on the
age and condition you can keep your old heads or use the ones you get
with the replacement. The marine exhaust valves are not critical.

Mercruiser Engine interchange - GM 305 V8
 

Yeah, my 3rd cousin once removed installed it.
JR


dave wrote:
Hello, I have a 1985 Welcraft 19’ with a chev 305 V8, the engine has
a cracked block, Water is getting into the combustion chamber and in
the oil, It’s shot!@!
I was told that this motor had been changed once before and that a
automotive 305 was installed, Is this true?,-----
Home Page: http://www.seanet.com/~jasonrnorth

Mercruiser Engine interchange - GM 305 V8
 

On Jun 2, 3:38*pm, wrote:
On Jun 2, 3:03*pm, "Jim" wrote:





"Richard Casady" wrote in message

.. .

On Mon, 2 Jun 2008 13:01:10 -0400, "Jim" wrote:

You pretty much want to start with *truck short block and move everything
from your old engine to it. Change out the casting *plugs and use new
marine
gaskets. Any block up to 1986 should work.

Don't you need a different cam? Or is the one for trucks close enough.

Casady

I'm pretty sure it's what's in the marinized block.

Double check to make sure you have the correct block as they did
change some in mid 80s. *One thing to look at is the angle of the
intake bolts. *In early years all the intake bolts were the same
angle. *Later on, the inside two bolts changed angles to tilt slightly
more upward. *Another change to look at is the rear seal. *The engine
went from a two piece rear seal to a special aluminum housing with a
one piece rear seal. *When this changed the bolt pattern on the end of
the crank changed as well.

Just about any of the small blocks pre or post 86 will bolt in place
of the engine you have. *If the rear seal is not the same then you
will have to get a different coupler. *I'd suggest looking for the 350
if you can instead of the 305 as the two are identical except for
displacement. *The truck and marine engines also used heavier block
castings.

You must replace the freeze plugs with brass ones.

The cam for marine is different but it is not critical to change.
Truck engines will have a closer cam than cars. *The marine cam has
slightly less overlap for improved low end and reduced backflow at
idle while still having a good bit of lift. *The most common small
block marine cam has .450 lift.

You will probably want to keep your intake if it is a cast iron 4
barrel one. *(Those are actually popular with some stock car
enthusasts in classes where aftermarket alluminum ones are not
allowed.) *If not then this is also an opportunity to switch to a 4
barrel carb. *It is ok to use after market aluminum intakes.

Most of the marine engines used the larger sodium filled exhaust
valves. *These are also found in some truck engines. *Depending on the
age and condition you can keep your old heads or use the ones you get
with the replacement. *The marine exhaust valves are not critical.- Hide quoted text -

- Show quoted text -

Oh and you really should use the marine gasket kit or at least buy the
marine felpro head gaskets if you take the heads off. That's the main
difference between the marine and regular gasket sets. If you're in
fresh water it won't matter much but if you're in salt water water the
marine head gaskets have a stainless steel ring around the cylinders
to keep corrosion from eating it.

Block crack from not winterizing?