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6.5 In a Boat ???

Dave01

Dave01

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I'm thinking about a project, just for fun, of putting a 6.5 in an inboard ski boat. I'd find a rough but functional hull, put it together with the help of a friend that is much better than me at wrenching. I have no huge performance expectations, just think it could be a neat project.

These boats usually have small block V8's in them, some with big block. If I'm right a small block weighs 550 lbs. or so, big block 700 lbs. Is a 6.5 TD around 900 lbs. without a lot of accessories? I'm sure the stringers would handle it, we could distribute the weight as needed, but certainly will change the way the hull handles.

HP and torque - if exhaust was 4" and open, decent lift pump, do FTB and marine injectors, very open intake, etc., would I expect around 225 HP and somewhere over 400 lb.-ft.?

Engine control - I'm very unclear on how the electronic side of things works. In a boat engine you just want to push the throttle and go. Any thoughts on the simplest way to set it up?

A Chevy 454 mates perfectly to several stock transmissions. Is a 6.5's configuration similar enough to make that work? I know a transmission guy who would probably enjoy the project, so I assume he could figure out a way to do it.

Fresh water cooling - I don't know how a 6.5 would react to that. You can still run a thermostat, but the water entering is cold, I don't know if that would cause problems. I'd run an oil cooler to be safe on that end. I certainly don't want to do closed loop cooling.

Is this a project that just shouldn't get started? Curious to hear what people think.
 
This is awesome! :thumbsup:

I have been wanting to put a 6.5 in a Correct Craft Martinique for a couple of years now.

The only thing really holding me back is I do not own a boat. :mad2:

There is two places that sale the marine version of the 6.5 in different horse power ratings.
 
I'll search for those 6.5 marine engines. I'm not interested in spending a lot of money on a boat-ready 6.5, just would end up too expensive I think. Then again, maybe it's just as expensive to try to build it! I'm assuming we could put together a decent running 6.5 for short money.

Uh oh, another Correct Craft guy? I own a '63, am looking at buying an '80's or '90's ski boat, have gotten back into skiiing the past 2 years. I won't even look at an inboard from another brand.

Since you know the boats, yes a Martinique would be a good platform. I was thinking of a Barefoot Nautique or Dominique, they are already set up for the 454 and have slightly more hull V, I think they would handle the weight better than a 2001 or similar. I woudn't rule out a '70's Nautique either. I'm wondering how much larger the motor box will have to be to fit the 6.5.
 
Dave,

This is too cool! I am looking for a CC right now. I had a '78 Nautique wish I never sold it...... I really want a Fish Nautique. They are hard to find. (may end up with a Shamrock...)

You will just have to jump over the engine cover I think. Just looking at my gasser suburbasaurus vs my friend's diesel, the diesel motor is significantly wider (I can see my frame rails from the top but not his.) I will try and pull a tape measure.

Will you be able to find marine application exhaust manifolds for the 6.5? (hmmm do they make a marine turbo? seems like the exhaust cooling would really kill the thermal efficiency of the turbo, might be a bad plan, but would look cool.)

The velvet drive would bolt right up. ( does the velvet drive care about rotation direction? most of the older gasser CC's used reverse rotation motors)

Would you want to cool directly from the body of water you are on, or run an intercooler? (watch the flow of the Jabsco compared to the HO waterpump requirements of a 6.5)

The prop will be fun! With that much torque, you can have a killer pitch!!! then dare any of the gasser guys to try and run your prop!

Wish I was closer, would love to help you wrench this one!

Hag
 
You bring up great points, and I don't know all the answers. The drive is no problem, you can get either rotation and just choose the rh or lh prop. Ratio is interesting - my '63 is 1:1, I know some of the modern ones are 1.23:1. In this case with the low rpm motor, and to avoid needing a huge prop that might not fit the hull, I wonder if I could find an overdrive transmission, maybe 1:1.25 or something similar.

I'd definitely want fresh water cooling, just seems to me it would add too much weight and complication to use a closed loop with a fresh water heat exchanger. But, maybe it would be necessary. The exhaust is my biggest question, I don't understand how to make it work. Standard non-jacketed manifolds would be so incredibly hot in a closed compartment that I don't think it's possible. I guess the answer is to research the marine 6.5's and see what they do.

I agree about the torque. My guess is it would be the most stable, effortless cruise or ski machine you could ask for. Not a huge top end speed, maybe a bit slower holeshot, but rock steady. The challenge is to try to prop it to give mid '30's at reasonable rpm's, would take some experimenting.
 
6.5's have long been a marine offering Peninsular has a big market on those also was a company I don't see in searches anymore for hammerhead & tigershark turbo/supercharged 6.5s good for 400 Hp. 6.2 or 6.5 set up correctly would make a great engine for a boat it just needs to be "marinized" for saltwater operating environment,
 
The 6.5 is actually lighter than a 454 by a few pounds, but once you get it rigged with a turbo and heat exchangers they come out a bit heavier. There are a couple of places now making marine water cooled manifolds for the 6.2/6.5 now. Add in a 92-93 6.5 DB2 from a truck with a turbo, supercharger, and since it's freshwater you could get by with raw water cooling you wopuld have a decent fuel sipping marine engine. For ski boats the supercharged engine is reccomended as the power is more instanious for throttle response to yank skiers shoulders out of place.
 
I looked at Peninsular's web site, lot's of info there. They sell a variety of power output's, have a parts manual pdf, and sell the parts. I'll call them to ask some questions about what is involved with marinizing a 6.5.

Here is what they show for an exhaust manifold, then the riser:
2335500.jpg

2335529.JPG


They have all the parts, but very expensive. I'll see what they say.
 
I don't know Buddy - an inboard ski boat has a doghouse motor box that fits pretty close to the engine. Even if it was made of material that wouldn't melt down, I don't know if you could get enough air flow to not have that box heat up like crazy.
 
Dave01 said:
I don't know Buddy - an inboard ski boat has a doghouse motor box that fits pretty close to the engine. Even if it was made of material that wouldn't melt down, I don't know if you could get enough air flow to not have that box heat up like crazy.
Click to expand...

I use to have a 85 Correct Craft Ski Nautique 2001 with a 351 Windsor. It would suck water out of the lake and through a filter and into the water pump. No matter how hard I ran her she never got so hot I could not open the dog house and get close to the motor. When you have an unlimited source of water to take away from I do not think you would ever have a problem of over heating unless you have a problem with your cooling system. This should be the same with any type of motor including a Diesel.
 
I agree on engine temp Marty, can't ever overheat with the raw water cooling. But, didn't your 351 have wet exhaust? Raw water cooling the manifolds and flowing out through the pipes? I'm thinking that regular vehicle manifolds would get way too hot to be in an enclosed space, I'd need to buy the wet exhaust.
 
Thats why you ceramic coat them real good to keep heat in. If you cool the exhaust it would get less turbo performance. But if thats what has to be done at least you can get the parts to do it.
 
Now I see what you are suggesting, I didn't understand. Maybe that would allow me to get away with standard manifolds.
 
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