MARINE INBOARD VS. REGULAR SMALL BLOCK
 

what is the difference between a regualr small block from a car/truck and a marine one? Thanks!

Re: MARINE INBOARD VS. REGULAR SMALL BLOCK
 

the basic blocks are the same as far as I know......
however, the gaskets are marinized as are the electrics
to prevent sparks that could ignite fuel vapor (alternator,
starter, distributor, ignition).....and the air intake uses
a flame arrestor for the same reason. Things like power steering, seawater pumps, remote oil filter kits are somewhat different too.....

Re: MARINE INBOARD VS. REGULAR SMALL BLOCK
 

The camshaft and intakes are also different since the power curve for an engine used in a road vehicle and one used in a boat are completely different.

Re: MARINE INBOARD VS. REGULAR SMALL BLOCK
 

thanks!!!

does anybody know what rpm range an inboard 23 wants to live at?

also any opinions out there or carbs vs. efi?

Re: MARINE INBOARD VS. REGULAR SMALL BLOCK
 

wot should be 42 to 4800 rpm's. i cruise mine at 3 to 3200 rpms for optimum fuel /speed - i have a friend with a 350/320 efi on his formula that really honks. I have a 350/270 carbed that does well also. Gary (Knot working) on this board also has efi and his boat runs right along as well.

Re: MARINE INBOARD VS. REGULAR SMALL BLOCK
 

a couple more things - first - I'm gonna guess we are talking about the ubiquitous 350 chevy small block -

if that's the case, the basic 350 block comes in two versions, the difference having to do with the number of bolts holding the crankshaft bearing caps in place - they are what is referred to a 2-bolt, or 4-bolt, mains. The 2 bolt mains are the common car variety blocks. The 4-bolt mains are used on the heavier trucks, and the high output motors like the Corvette - these are also sought after by drag race guys, as they are much stronger.

To my knowledge, the blocks that are diverted to marine industry use up front, ie. that go to Mercruiser et al, are all 4-bolt mains blocks, to provide increased reliability - the typical boat useage does place a higher continuous stress level on a motor - cranking along at 3000 to 4000 rpm for long periods under load, where the average car use would be floating along at 2000 rpm, under a lighter, rolling resistance, loading.

Also, for the 350 small blocks, depending on the vintage, as these have been around for half of forever, there are a variety of heads available, depending on carburated, or FI, and these contain different configuration intake and exhaust ports, and often different sized valves, from each other - the high output Corvette motors, for example, use different heads than a sedan or station wagon motor.

Along with all that is the already mentioned camshaft differences, and the marinized electrics, starter, distributor, etc.

hope that helps some.

Bill

Re: MARINE INBOARD VS. REGULAR SMALL BLOCK
 

we are indeed. it is a crusader 310 i believe and it is going to get looked at in the next few weeks by my buddy who should be chiming in here.......

additonally we are going to put a 383 in it in feb. which is why i was asking about the differences.

any opionions on a 17/15 3 blade vs. a 16/15?

thanks!

Re: MARINE INBOARD VS. REGULAR SMALL BLOCK
 

I hang with kmodi.

We're thinking about building a 375hp 383 stroker for his 23cc. If any one has any experience with hot small blocks in these boats, feel free to chime in. I know of a Silver Hawk with a 377 that seems to go great. The two boats are very similar so it should be a decent indication. Again, any info or advise would be great.

Re: MARINE INBOARD VS. REGULAR SMALL BLOCK
 

are you guys building your own, or gonna buy a crate motor ?

I think I'd call Summit Racing, they do crate motors, tell them what you're doing and ask for a 383 stroker done up as a marine engine, specify a block with 4-bolt mains - though I think all their strokers are done that way anyways - that would be the fastest best trip to that end result.

Bill

Re: MARINE INBOARD VS. REGULAR SMALL BLOCK
 

Your going to have to be very carful when building engines that out of the norm for a boat. your cooling capacity is reduced on boats due to engine enclosure and open or closed water systems. The hot rod motors you put in a car are not the same as the hot rod marine engines. My father-in-law built a 383 stroker for a searay and i tryed to tell him to call in for outside help, but son-in-laws opinions arn't much good apparently...... he should of asked for help.. you can't use standerd rv cams in marine aplications. Ask for as much imput as you can get from marine mechanics. Remember no is always free.

Re: MARINE INBOARD VS. REGULAR SMALL BLOCK
 

back in the eighties a lot of folks down my way were putting big blocks (454's) in both their inboards and i/o's. Bottom line was too much weight and i dont know if there are any left around here with that configuration. i would also make sure you had the heavy dutier gear than its sister- i dont remember the series off hand- with that lighter weight and all those extra horses she ought to run good. I dont think the pocket drive inboards can handle 40 knots though either. Maybe gary will chime in here-

Re: MARINE INBOARD VS. REGULAR SMALL BLOCK
 

One thing to remember is if it's raw water-cooled then you will need to use brass freeze plugs. Also you would really need to watch your sustained RPM's being a 383 has such a long stroke (same stroke as a SB 400). My dad put a couple of small block 400's in a 31ft Baha fishing boat and they held up pretty good but the guy seldom ran them over 3200 RPMs.

Re: MARINE INBOARD VS. REGULAR SMALL BLOCK
 

Also a hot rod engine has to be torn down and refresh every so often. They use thin rings to prevent breakage,but wear out faster but can handle the revs,less drag on the cylinder wall= More HP.And you would have to use a higher grade of gas.My choice would be a stock engine.Will give you more hours and the best bang for your buck.

Re: MARINE INBOARD VS. REGULAR SMALL BLOCK
 

Thanks for the replies. It's a little dangerous to toss around terms like "hot rod engine". I'm talking about a mild 383 with a standard ring pack, little hydro-roller cam and a pair of vortex heads. Not exactly ground braking. A motor like this could live and make max power at 3200rpm for life times. That said, it may very well not be needed. A GM crate long block w/ the existing accesories might serve the purpose. Time will tell. I'll have the boat in my shop today or tomorrow and will go from there.

Re: MARINE INBOARD VS. REGULAR SMALL BLOCK
 

I have a Marine Power 350 HP (CARB), and max speed is 37, I don't have to worry about trouble shooting this motor because I can figure it out like I always have. I have a friend with a throttle body and he spent around two weeks replacing everything until it was right again. Also you will require a return line for gas since it's around 42 lbs of pressure. The same guy had a red 76 454 with a lot of HP and it would run around 50, but wasn't really good over 40 mph.

Re: MARINE INBOARD VS. REGULAR SMALL BLOCK
 

Thanks for the info. The goal is for this boat to cruise between 25-30 and be as fuel effient as possible while sticking with a carb. I figured that the low rpm torque of a 383 would be a good fit. Conversely, I bet a ZZ crate long block from GM would get us to the same goal.

Last I heard, the boat and her owner had been sitting behind a rolled over semi for 2 hours and the highway patrol were predicting another 4! Fun way to spend the night.

Re: MARINE INBOARD VS. REGULAR SMALL BLOCK
 

I had a friend who is also a marine mechanic who put a car motor in for a guy and it took forever to get the rpm's and it running right, he swear's he would not do that again.

Re: MARINE INBOARD VS. REGULAR SMALL BLOCK
 

the GM HT383 engiine should be perfect for use in an inboard aplication, its tailored for a flat tourque curve( just what you want in an inboard engine), can't understand why Mercury continually builds its own 383 out of 5.7 engines rather than use the HT383