Car Motor >> Boat Motor, any ideas how much to convert???

[FISHIN SUCKS]

Got a question, what all does it take to convert a 351 Windsor car motor into a boat motor? I realize you would need a marine intake manifold and a pair of water jackets/headers, but what else? Does anyone on the board here have the necessary parts for sale to make this change? Okay, here's where it get's scary, my customer's employee blew up his 2.5L in his '87 21' bayliner and he has this 351 laying around with 40k miles on it. I advised him that this sounds like a stupid idea but this is a run what ya brung kind of deal or monster garage in Onsted, MI (hey Doug L, did you catch that). I told him that I'm not so sure the stringers could even handle the torque. Thanx in advance for any input,

tom

[MOP]

OK pistons are different, core casting plugs(Freeze Plugs) need to be changed to brass and the cam is different! Ok now that being said several years back I had a client blow his 350 up and did not want to part with the $$$$ to do it right!!! He brought me a 350 out of one of his trucks that was wrecked, tho the best of my knowledge he is still running it. Now the caviate!!! he just uses the boat foe fishing and runs it pretty easy, if he was anything like a normal Donzite it would have puked post haste!!!

Phil

[Doug L.]

Hi Tom,

Small world!

I have a 302 Mercruiser and drive that would go in that
boat.

Send me your email address, I have some photos for you
from past aoth and kart racing.

Doug:)

[f_inscreenname]

Brass freeze plugs, maybe cam (most boat cams are just truck cams), if you have a cast iron intake there is no difference, distributor (no vac advance) must be marine, Carb, water pump (must be cast iron) and anything else that is a “bolt on” will have to come from the old motor or at least be marine. You will also need a manual flywheel to fit inside your bell housing. Basically you can use the block, crank, rods, pistons, heads, intake (if cast iron) or you could even use a aluminum intake like I am.
Every one (but the 454 I am building now) of my motors have started life as a truck motor of some sort. Even the last 351W I built came out of a pick up truck. Its easy to make it marine and it would be even easier when you rebuild it. A 40,000 mile motor is not ready for a boat. Needing to change the cam (if needed) and freeze plugs you are only a couple steps from rings and bearings. No reason not to do it.
I do see a major problem though.
“ blew up his 2.5L in his '87 21' bayliner”
That drive (what ever it is) is not built for a V-8. I am sure the gear ratio will be way off.
I’m also sure I am missing a couple things and if you really want to do it I will give you step by step but its late.
PS If I had a 351W the only thing I would use a 302 for is parts (no disrespect Doug). The 351W is one of the good ones.:yes:

[travisgoff]

The fuel pump should be marine if it is mechanical, or use an electric fuel pump with a pressure regulator. The reason is that when/if a mechanical fuel pump diaphram fails, it could leak fuel into the bildge and blow up, (worst case scenario of course). Marine fuel pumps have a second tube that goes back into the carb should the diaphram get a hole.

Just my two cents.

-Travis

[jdp_509]

I Thought The Oil Pan Was Diiffernt Also. The Marine Oil Pan Has Baffles In To Keep The Oil Free Sloshing Around So Freely In Rough Waters.

[f_inscreenname]

Most 351W's are rear sump and they will work fine. Just make sure its painted real good the prevent it from rusting out.

[FISHIN SUCKS]

Thanx to all of you for the for the input, talk about an education:eek!: ! I'll give my buddy the down-low. Sounds to me like putting this 351W into this bayliner is like putting a hundred dollar shine on a 2 dollar pair of boots:yes: .

The thing I was thinking on the intake was that I thought that where the carburator sits, there is more of an angle to compensate for the angle of the boat while in the water:confused: . Can somebody re-educate me on this one if needed? Thanx again for the hep,

tom

ps Hey Doug, I'll PM ya!

[f_inscreenname]

As long as it sits semi level when in the water (at the dock) your cool. I don't think I/O would have that much slant anyways. If needed you can get a carb adapter for a ski boat (inboard) and they will give you all the angle you would need.

[FISHIN SUCKS]

Thanx f

[Tom Davis]

If you want to give "Blown up motor and Boat" a whole new meaning just leave the original non-marine starter in there! NO No No! One of the most important things to remember to change out is the starter! Marine starters are sealed so none of those pesky little sparks get out and ignite the gas fumes in your enclosed bilge! :eek!: :eek!: :eek!:

Just my .02

Tom Davis
Winni Bandits

[handfulz28]

MOST important: USCG approved starter, alternator, carb, fuel pump, fuel lines, distibutor, coil, whatever might cause it to really "blow up".
Marine manifolds would probably be easy to come by.
Changing/making sure brass freeze plugs are in is a good idea.
It's not absolutely necessary to change cam/intake; but of course performance may suffer.
But after spending all the money to get this stuff, can the 2.5 not be rebuilt?

[Craig S]

The thing I was thinking on the intake was that I thought that where the carburator sits, there is more of an angle to compensate for the angle of the boat while in the water:confused: . Can somebody re-educate me on this one if needed? Thanx again for the hep,
tom
ps Hey Doug, I'll PM ya!

Yea, I switched intakes (from dual side drafts to a single down draft Holley) on one of my Centurys...a Resorter. Due to the severe angle (a short boat with a straight inboard), I had to buy a wedge from Summitt to fit between the Holley and the intake on the mighty Ford Y-block. But, yea, thats because I needed to get it pretty level when sitting and running. Its just a test of reasonableness on how level it is...not rocket science.

[Rootsy]

just some of the things that come to mind...

internally, if building an engine from the ground up.

-Increased piston to bore clearance
-Compression ratios (older engines more so than newer stuff)
-Top ring gap increased clearance
-Intake and Exhaust valve material
-Camshaft profile
-Windage Tray
-Baffles in oil pan... the stock one isn't much of a baffle if you even want to call it that
-Composite or Stainless Steel core Head gaskets

Externally....

-Flywheel for merc stuff
-Sealed Alternator
-Sealed starter
-Vented distributor and sealed ignition box

Carburetion...

on a holley or BG i like to add baffles to the float bowls as well as spring loaded needle and seat assemblies if they don't come that way already... J vents are a must... and a marine carburetor will have sealed throttle shafts to keep fuel from leaking out onto the manifold... in a nutshell... as well as some metering system alterations vs auto applications.

In fresh water aluminum intake manifolds are fine... heck aluminum heads are fine for the most part... since i've never boated really in salt water... i can't give a definitive answer as to longevity...

and so on and so forth... but that is a brief overview...

for the most part merc's short blocks aren't really any different that those found in the GM and Chevy pickup truck...