340 boat motor questions

So I just got a pretty cool old boat with a 340, all the core plugs popped out so I pulled the intake and had cracked lifter valley. It is reverse rotation but only has about 20hrs on the boat. Can I just get the block brazed up and re-assemble and run it? This would save me the cost of buying a 340 block, boring it and buying pistons. If not can I just throw a 360 in it and run that with the reverse rotation cam from the 340? I am aware the rear main knurling on the crank is different, will it leak bad enough to worry about or can I just go with it and add a little oil every few times out? What about a 69 340/416 stroker motor sitting around the shop wasting space, can I just throw that in or is the prop and everything going to be totally wrong now? I am a little suprised the 340 has 318 port sizes n the intake and heads, is that how the marine motors were made or has someone swapped stuff around?

If it's beyond fixing... What if I decide to just sell the parts, are they worth anything? Marine manifolds, prop, bellhousing...

Just put another block in it... sounds like
it was froze a couple of times... just set
up the block like it was stock but change the
top end with the marine stuff.. I use to own
a old Chis Craft that was a reverse rotation
that was a PITA .. I didnt know it was a
reverse rotation engine till I got it apart

perfect std bore 340s are expensive around here if it's even possible to find one, even one that will clean up at a reasonable bore is hard to find and expensive ($500-600) then boring and buying pistons.

I just pulled the heads and they are open chamber small port heads, I bet a 318 with a compresison bump will make nearly the same power and I could ue the forged reverse rotation crank. The pistons are low compression 4 valve relief 73 type. The intake looks like a 274 4bbl but says "marine" on the bottom, perhaps I should just throw in my 273 HP engine with the backwards cam and crank, I don't need it to be fast, fuel efficency would probably be more usefull to me if it would make enough power.

Funny thing, this is the only Fury I ever seen or heard of with a 340 from the factory. It's called a ski fury.

https://kalispell.craigslist.org/boa/6146693813.html

this is the boat I bought, I just want a cool little boat to go fishing or cruising with the wife

Can I just run the trans in reverse and put a normal engine in along with a normal water pimp?

On my boat the crank was just a stock crack
and the cam was different..from what I remember

Cam is different, oil pump drive, distributor, piston pin off-set, The critical part would be the exhaust manifolds. If they are cracked, put it back on craigslist.

I don't know boats (tho I worked a bit once on a reverse rotation 318 outboard speedboat) but I'd sure consider one of these. I wouldn't sweat the knurl potential. EDIT I wouldn't think the piston thrust would be a problem but not sure how the oil pump would fare tho I'm sure there are solutions as its obviously already been done in the boating world.

Melling only place that has a cam if you need one
stick a 318 in there with the backwards boat only stuff ---get a good looking girl in a bikini to ride with you and it won't matter how it runs

if you put a forward knurl crank in a reverse motor your main seal will leak like Comey investigation.

Is it an I/O or full inboard and you know for sure it's reverse rotation?

A regular rotation engine should work in there with just a prop change and if it's an I/O, a water pump impeller change. Not sure if a Velvetdrive cares which direction it's turned or not but that would likely be just a pump change too if it's a full inboard.

I don't see the advantage to reverse rotation on a single screw boat and a lot of them weren't. It was usually a twin screw deal that one was reversed.

Kevin.

Get a good 318, just change cranks and do a balance job, you'll never know the difference. Are you sure it's a 340? That would be a fifty year old engine-boat. A lot of 318s where used up into the ninety's, maybe later. Did it have its own cooling system or fresh water. If cooled from the water itself the block, risers, heads could be junk anyway from sea-fresh water. It doesn't take long to eat them up, especially if setting awhile.
Been setting here thinking about the two 400 engines we replaced in pops boat, thinkng about the cams. I can't remember how they where made different but I know both dist turned in same direction. Maybe it'll come to me later, brain fade!

Thats what I was thinking.. a single screw
and a reverse direction engine.. just doesnt
make a lot of cents to me... as said.. put a
engine in it and change the prop... yet my old
Chris was a reverse rotation single screw

Definately reverse rotation, has a sticker on front of engine, sticker on transmission, distributor has a spacer block to hold the oil pump drive down, water pump blades are reverse rotation, prop is reverse rotation...

Definately a 340, 73 block.

Don't know difference between in/board vs in/out

It sucks in lake water for cooling, looks to be almost no rust in water jackets and manifolds are not cracked and in really good condition. Prop looks almost new with just a few scratches on the edge of one blade.

A I/O= Inboard/outboard(the drive unit is on
the transom.. a inboard has the whole thing
on the inside of the hull with just a shaft
and prop under the hull.. yours looks like
a inboard set up
EDIT
Yours is a inboard

https://boats-from-usa.com/not-specified/century-ski-fury-ski-boat-10618

If the exhaust manifolds are shot, put the thing back up for sale. Even if they're not, you would be $ ahead putting the thing back up for sale. That project boat looks like one big black hole to me. I like boats and the inboard is cool but you have to know when to call it.

To answer your questions, you can't just run the drive in reverse, well not for long anyway. Depending on the drive, they have an internal oil pump that doesn't pump in reverse. Depending on the drive (paragon? velvet?) they can be reconfigured to change the input direction. If you do that, you can basically plunk in a garden variety small block and that may be cheaper than re-configuring a SB to reverse rotation.

Use the stroker get the original cam reground a bit. Have fun. Or those pistons and a 360 will give you quench and some compression to play with loose the small port heads you will not need them for torque. Boats also are great for turbo air to water inter-cooled fun.......

I think you need to determine what kind of time and money this is really worth to you. As mentioned, 318's are easiest fix. I just finished a STD rotation 360 boat engine, and I am pulling 2 more 318's this weekend. The crank must be reverse rotation, as is the cam, as you know. The knurling cant be " fixed" to run backwards. Maybe someone has a secret silver bullet fix, but not that I know of. I can tell you, parts for older Chrysler marine engines are very difficult to find at a reasonable price, and quite simply, some of them are just hard to find period. If it uses raw fresh water, thats a bit more challenging ( whatever you do, be very careful with the little cast flanges that mount the raw water pump, which is actually the water pump " cover". They break very easily, and are NOT easy or cheap to get)than engine water, although you'll have exchanges etc at that point.Again, I think it comes down to how much to spend, vs maybe just grabbing an easier to find RVS ROT 318, and go have fun. If you were closer, I could hook you up on a 318 reverse. Best of luck.

I wonder if this is my brothers old boat. Does it have Michigan registration on it? Put a standard rotation 360 in it and a new ACME prop.

Robert,

I am considering purchasing a Marinette boat with twin Chrysler smallblocks. Going to build both engines with magnum conversion and higher compression. The engines on these use raw water cooling and run at lower temperature because of this so compression increase should be no trouble. Most marinas in my area have 89-90 octane so fuel would be ok.
A magnum headed 318 with higher compression would run as well as the smogged out 340 you have and be much more efficient. Just my 2 cents.