your opinion

[barnyard]

currently rebuilding 350SBC for my 93 larson. considering converting to closed cooling if i can find donor boat/motor. what year did Mercruiser introduce for 350 carburated? Your thoughts? Salt water

 

[Scott Danforth]

the 350 with a carb has been around since the late 60's in boats

However, your current motor is a 1986-1995 vintage
your drive is a post 1992

if it was me, I would be taking your current block, vortec heads (1996 and later), a stroker crank/rods, LCQ style pistons and build a 6.2

 

[barnyard]

currently rebuilding 350SBC for my 93 larson. considering converting to closed cooling if i can find donor boat/motor. what year did Mercruiser introduce for 350 carburated? Your thoughts? Salt water

Edit: have 97 block,vortec heads,roller

 

[bigblocksarefun]

Either rebuild as a stroker or pick up a stroker short or long block. Closed loop cooling systems have been around forever. Considering the year you have, you can probably order the parts needed.

 

[Scott Danforth]

Get a new heat exchanger kit from Orca or similar

Mercruiser has has 20-30 different heat exchanger setups on the SBC alone between the early 70s and 2000s

Being a 1997 you already have vortec heads.

 

[Scott06]

currently rebuilding 350SBC for my 93 larson. considering converting to closed cooling if i can find donor boat/motor. what year did Mercruiser introduce for 350 carburated? Your thoughts? Salt water

In salt water is a great addition , especially if you can do a full system. By donor - do you mean yo are looking for a used system? I think you will find more aftermarket system than factory installs.

places like michigan motorz can set you up with a complete system. I think they are a $1500-2k adder to their engine packages. Just make sure the debris and corrosion on the inside of the block gets removed via hot tanking or similar. will plug heat exchanger if not fully removed

 

[QBhoy]

Is she a Larson cabin cruiser or similar ? Or perhaps a smaller open bowrider?
Either way…I’m maybe thinking or wondering if there would be any point in going down the stroker or power crazy road. Would the financial outlay and extra thirst be worth it on a cruiser ? Or would it be handled by a standard hull type, found on a Larson speedboat?
A 350 vortec with a normal 4 barrel carb is plenty enough for most. Or even if she had a Holley 4 barrel and a sound ignition system added…you’ll still get about 300hp or close for cheap.

 

[Pmt133]

I'll add that if the crank needs work you end up at the same price for a stroker vs a 350. I picked up a 3.80 inch forged crank for less than $300... between everything else the 388 I am ready to build for my car cost like $600 including the block. All forged internals are overkill for it and really overkill for a boat but if you have to buy new parts, the point I am trying to make is like was said... there really is little to no cost difference.

I'm in the camp of I'd rather have the extra power and not need it than not have it and wish I did.

 

[Scott Danforth]

just to add to the conversation.

a brand new crank costs $30 less than having your existing crank turned at a machine shop
a brand new stroker crank cost the same as a stock stroke crank
forged H-beam rods cost less than refurbishing stock rods
new pistons between a 355 build and 383 build are the same cost

with all new parts (block, heads, crank, cam, etc), the cost difference between building a 377 cubic inch and a 350 cubic inch motor is about $25

a half system is better than raw water (and does not require an additional pump if you have an alpha drive)
a full-system requires a second pump if you have an alpha drive

determine what you want for a motor, plan out every detail.

 

[QBhoy]

I presumed he was using the block he had and rebuilding ? Not starting from scratch.
The former being the case, it’s going to cost more than $25 different. There will be the matter of the actual “stroking” to account for, at the least.

 

[Scott Danforth]

I presumed he was using the block he had and rebuilding ? Not starting from scratch.
The former being the case, it’s going to cost more than $25 different. There will be the matter of the actual “stroking” to account for, at the least.

Not really. If you have to machine the crank.... resize the rods and get new pistons.....it is cheaper to buy new than machine the old. There are a few cheap machine shops that are the exception. However at that point, a stroker rotating assembly is about same $ as stock stroke length.

20 minutes with a die grinder will clearance the pan rail for the longer crank throw

Now if you are not touching the short block, then you are not "rebuilding"

 

[Pmt133]

I'll go on to add that on the later vortec 880 casting blocks (not what we're talking about here) you can sometimes get away without any grinding if you use "stroker rods" which most aftermarket ones are now... however some of the late 880 blocks have shorter bores than a typical SBC so you have to check that as well. Again, it doesn't sound like the OP is using that... I'd personally be looking for a 1 piece rear main block that's machined for factory roller lifters and be done with it.

My machine shop doesn't charge for stroker clearance work if they're doing the rest of the work on the block. They claim they do it so often it takes them only a few minutes on top of all the rest of the work and honing. I think even when they do it's 25$. And yes, you can easily do it yourself.

 

[QBhoy]

Not really. If you have to machine the crank.... resize the rods and get new pistons.....it is cheaper to buy new than machine the old. There are a few cheap machine shops that are the exception. However at that point, a stroker rotating assembly is about same $ as stock stroke length.

20 minutes with a die grinder will clearance the pan rail for the longer crank throw

Now if you are not touching the short block, then you are not "rebuilding"

Fair point. Not something I’m familiar with or even a common thing over here. Can only dream of such a thing !
Just presumed the guy was doing what he could with what he had currently.
Over here fuel consumption versus power gain is a big deal I suppose. Along with not readily available parts or shops with the ability to do so.
If he is putting it in a fast hull..:stroker all the way…if in a 25-30ft cruiser…might not be a sensible thing…here at least.
I’ve been searching for a mint condition 6.2 mpi to replace my smaller v8 mpi for years now. Not once have I came across one worth considering , if at all.

 

[Scott Danforth]

Actually, in a fast hull, I wouldn't build a stroker. But a high RPM big-bore, short stroke. Either keeping the 3.48 stock stroke, or dropping down to 3-1/4" stroke for 327

You want a stroker for torque in the big boats

 

[Davetowz]

https://www.mrcool.us/fresh-water-cooling-kits.html Give these guys a call, I installed one of there kits on a similar vintage 350. They have great customer service.