350 DD boat

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Barefootduck
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350 DD boat

Post by Barefootduck »

Got a new hull to start fresh and put my 350 on. Going to start Cleaning up the hull and paint it in the next few weeks. 12ft gililoeo
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Keeth1123
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Re: 350 DD boat

Post by Keeth1123 »

Nice! I still miss my DD350 from time to time.
:old_glory:

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Barefootduck
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Re: 350 DD boat

Post by Barefootduck »

Keeth1123 wrote:Nice! I still miss my DD350 from time to time.
If it gets about the same economy as that 305 DD but will get the prop turnin more I’ll be happy
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Re: 350 DD boat

Post by kwanjangnihm »

BFD did you make any mods to the 350?
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Re: 350 DD boat

Post by John Fenner »

Re cam it with a Mellings CS-711 camshaft, a set of 305 Truck heads or if you can find a set of 267 small block heads even better, a stock 305 egr 4 barrel aluminum intake adapted to a 390 Holley with a secondary metering plate jetted 65 primary and 72 secondary will snap a 72" prop hard.
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Re: 350 DD boat

Post by Barefootduck »

kwanjangnihm wrote:BFD did you make any mods to the 350?
No not yet, it has an edelbrock performer Intake. Supposedly a GM performer crate motor. I was going to change the cam and run it see how it does. I have the 305 that I’ve been running so y’all are saying I could use those heads? The 305 is Out of a 85 c10. Have a 72x36 stick prop that I’ll be running so that’s what I’m trying to be able to spin up.
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Re: 350 DD boat

Post by Barefootduck »

Got started on the hull. Removed the old deck because some rot, but forgot to take a picture after the actual wood was removed. Lol the glass was delaminated so bad a cut around and a pulled removed it from the wood. new one cut out, ordered resin and already have the glass. The kickpanel part of the deck is still good. Also glued in some wooden dowel rods into the old rigging holes, and will be running a piece of glass over them. Poly looks to be pretty new.. the old rigging had some homemade stringer jacks, are they worth having them on fiberglass hull? Did some searching on here and either glass or aluminum said it helped on dry, and even in the deeper water. Just curious
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Barefootduck
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Re: 350 DD boat

Post by Barefootduck »

John Fenner wrote:Re cam it with a Mellings CS-711 camshaft, a set of 305 Truck heads or if you can find a set of 267 small block heads even better, a stock 305 egr 4 barrel aluminum intake adapted to a 390 Holley with a secondary metering plate jetted 65 primary and 72 secondary will snap a 72" prop hard.
Is the edelbrock performer aluminum intake similar?
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Slidin Gator
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Re: 350 DD boat

Post by Slidin Gator »

The 305 heads have smaller combustion chambers so you get higher compression. Depending on how willing you are to pay for premium fuel, you are looking for 58 cc chambers and flat top (max compression) or dished pistons (a bit lower compression). Doomed pistons will put you into race or Aviation fuel. 305 heads also have smaller runners so you get higher velocity at DD rpm’s.

Pull off the valve covers and find the casting number to look up what you have. Here is one link:
https://outintheshop.com/faq/casting/heads.html

The Edelbrock Performer should work fine, is it a square or QJet pad? Don’t be afraid of an adapter spacer, that will help make torque.

Follow Johns input on carb and cam for max performance. The Q jet you are running on the 305 will also work if tuned right, but it’s a bit big for the application, like you have already learned.

Sounds like you have most of what you need to make a fine motor. Quit being cheap on the prop though. Save your pennies for a carbon fiber prop and make a wall hanger out of that stick, you will be glad you did.
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Re: 350 DD boat

Post by airduds »

Best of luck but you won't run the hill with that combo.
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Re: 350 DD boat

Post by Barefootduck »

airduds wrote:Best of luck but you won't run the hill with that combo.
Right on, been running a 305 on a heavier hull turning that prop 2200-2300 so it can only get better lol.
Plan to run this awhile then sell and go reduction or A/C but that will be in the future. Just getting started in this so it is what it is
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Re: 350 DD boat

Post by Barefootduck »

Didn’t get as far as I wanted because I decided to cut out the wood in the kick panel good thing I did the bottom was rotted out underneath the tabbing so made the new wood coated in resin and got the deck coated and layer of glass on the bottom. Next weekend will be the install of kickpanel and deck tabbing and dealing with glass hopefully
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Re: 350 DD boat

Post by Barefootduck »

What would be the best prop for a SB DIrect drive. I have been reading posts about waterthunders Dd ls and he ran a short three blade carbon? Apparently producing thrust up to 3500 rpm? Anyone have any input of this or know more about it. Now I’m not saying I would be pushing the HP or torque he was but a prop that is safe and still producing thrust over 3k rpm would help in any DD application. I’m just curious to be looking for an alternative when I get the boat going again and want to upgrade from the woody.

Thanks
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Re: 350 DD boat

Post by Barefootduck »

Side note, started glassing in the kick panel maybe this weekend I’ll finish up the deck.
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Re: 350 DD boat

Post by Barefootduck »

First layer of tabbing
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Re: 350 DD boat

Post by SWAMPHUNTER45 »

Looks like you are making some progress with the repairs!

As far as the prop goes there are plenty of guys who have run DD 350s and 305s so search the threads. I suggest a two blade prop like a Q as it will give you the ability to adjust pitch and performs well for push and speed. Don't get hemped up on spinning it higher than what is a safe rpm or it will bite you.

Look up OleMan on here he runs a 305 with a wood prop and it does well for him.

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Re: 350 DD boat

Post by Barefootduck »

SWAMPHUNTER45 wrote:Looks like you are making some progress with the repairs!

As far as the prop goes there are plenty of guys who have run DD 350s and 305s so search the threads. I suggest a two blade prop like a Q as it will give you the ability to adjust pitch and performs well for push and speed. Don't get hemped up on spinning it higher than what is a safe rpm or it will bite you.

Look up OleMan on here he runs a 305 with a wood prop and it does well for him.
Yea I wouldn’t spin a prop over the specified rpm. But that’s what I was curious about because I’m sure waterthunder mentioned his turning 3500 rpm. Was somthing like a 66in? My prop says 2700 rpm max on the paperwork when I got it so that’s what I’ll stick too.

Thanks I’ll check it out
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Re: 350 DD boat

Post by SWAMPHUNTER45 »

OneEyeGator has a chart that takes the diameter of the blade and rpm to factor blade speed. Maybe talk with him but anything Dave WT does is going to be high end. He does R&D with Sensenich so my bet is that they got him hooked up with something special.

What prop you have now Duck and why the need to change?

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Re: 350 DD boat

Post by SWAMPHUNTER45 »

The hull jacks help tune the boats bottom so I like having the jacks in place and would keep them. It is not just a dry ground thing actually they can help a boat to stop hopping or get it off it's nose depending on where they are put and how they are applied.

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Re: 350 DD boat

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SWAMPHUNTER45 wrote:OneEyeGator has a chart that takes the diameter of the blade and rpm to factor blade speed. Maybe talk with him but anything Dave WT does is going to be high end. He does R&D with Sensenich so my bet is that they got him hooked up with something special.

What prop you have now Duck and why the need to change?
Yea if I remember right he said it was cut down. Not sure what that entails. Lol. But I have a brand new sensenich 72x36 stick. Got it last December and ran it on my 305 boat only turnin 2200 give or take. Plan was to run a 350 so that’s why i went over propped for the 305. It ran good only turnin 2200.i was just looking for future ideas you know. And yea I’m definitely going to keep the floor jacks in the new hull. Think it’s a great idea. Do you have any experience with where to locate the jacks? And I tried to find oleman on here and didn’t come up with much and nothing about a 305?

That’s the heavy boat I was running the 305 on. Someone poured resin to cover the poly bolts and it’s thick. Real thick. I built the cage and set it up last December.
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Re: 350 DD boat

Post by SWAMPHUNTER45 »

With Direct Drive STROKE is the most important engine factor. If you could get a 383 or an old 400 sbc you will get a good little boost in torque.

Do you understand why the stroke is more important to obtain your torque need?

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Re: 350 DD boat

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SWAMPHUNTER45 wrote:With Direct Drive STROKE is the most important engine factor. If you could get a 383 or an old 400 sbc you will get a good little boost in torque.

Do you understand why the stroke is more important to obtain your torque need?
Longer stroke makes more power at lower rpm
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Re: 350 DD boat

Post by SWAMPHUNTER45 »

So your 305 and the 350 share the same stroke that being 3.48 inches. The gain in cubic inches comes from a larger bore diameter which will yield "some" gain in power but not on par with a gain in cubic inches obtained by a longer stroke. The 383 uses a longer stroke that being 3.78 which equates to three tenths of an inch more stroke.

The stroke is the length of the pistons movement and as such a longer stroke affords the piston to be pushed down longer in the "power" cycle of the crankshaft. The longer stroke will build more power in any engine. The reason why it is often cast as low rpm power is the higher rpm you run on a stroker the more critical the piston speed is in the mix.

So a 383 would be the same weight as the 350 but bring more stroke to the mix which in turn will provide you more usable power.

I am a Caddy fan. Did you know that Cadillac "stroked" the 472 to yield more torque for the "Eldorado" and in turn created the 500 !
The stroke of the 472 was lengthened from 4.06 to 4.304 (.244 longer) in the 500 in doing that they gained 25 ft pounds of torque at 3000 rpm.

If this is something within your budget a 383 would help you obtain usable power at a fairly affordable cost.

I have been in OleMans boat with his son and with the three of us it would plane out. She wont run the hill loaded but we really would not expect it to. They got many years of service out of their old 305. They are hoping one day to go to a Caddy 425 engine they have put up.

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Re: 350 DD boat

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[quote="SWAMPHUNTER45"]So your 305 and the 350 share the same stroke that being 3.48 inches. The gain in cubic inches comes from a larger bore diameter which will yield "some" gain in power but not on par with a gain in cubic inches obtained by a longer stroke. The 383 uses a longer stroke that being 3.78 which equates to three tenths of an inch more stroke.

The stroke is the length of the pistons movement and as such a longer stroke affords the piston to be pushed down longer in the "power" cycle of the crankshaft. The longer stroke will build more power in any engine. The reason why it is often cast as low rpm power is the higher rpm you run on a stroker the more critical the piston speed is in the mix.

So a 383 would be the same weight as the 350 but bring more stroke to the mix which in turn will provide you more usable power.

I am a Caddy fan. Did you know that Cadillac "stroked" the 472 to yield more torque for the "Eldorado" and in turn created the 500 !
The stroke of the 472 was lengthened from 4.06 to 4.304 (.244 longer) in the 500 in doing that they gained 25 ft pounds of torque at 3000 rpm.

If this is something within your budget a 383 would help you obtain usable power at a fairly affordable cost.

I have been in OleMans boat with his son and with the three of us it would plane out. She wont run the hill loaded but we really would not expect it to. They got many years of service out of their old 305. They are hoping one day to go to a Caddy 425 engine they have put up

No I didn’t know that. Now I do I like this kind of information, and yea my 305 would plane out three guys. So I’m just aiming to try to get closer to my Mac rpm with the 350! Then I can upgrade from there. I assume prop thrust isn’t linear right? Like it’s more of a sharp increase then a steady increase with the rpm?,
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Re: 350 DD boat

Post by SWAMPHUNTER45 »

I believe that every engine based on it design and component spec will respond differently.

In testing and real world use I can tell you that in a direct drive application that getting 25 to 35 additional "pound foot" of torque is noticeable on the tachometer. Depending on the prop it can be an additional 40 to 150 rpm so it matters.


You go from a 305 with hours on it to a properly built 383 you will see a gain in push I am sure.

The 350 probably a small gain but more will depend on its condition and tune as the stroke is equal.

In this case 305 vs 350 it is only the additional 45 cubic inches of volume divided by 8 cylinders as the boost. A more powerful explosion but not a longer duration of power transfer.

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