Do I really "need" twin carbs????
 

Had to much time to think today....
Thinking about if I am going to really need two carbs on the boat motor....
With the 0.125 over bore on the 8BA block I will be about 4.2 litres... Bigger than the long stroke Merc that was rated at 125hp which is more than boats this size had in the 1930's...

Spec plan would be.....
4.2 litres.
After big pistons, Canadian heads and a head skim I will have 8.0:1 ish compression.
Might even just run the 8mm lift 8BA cam...
Simple cleaning up of the ports and careful matching of manifold.
Better electronic ignition inside a divers helmet dizzy.

Thinking about one 1 1/16 dual throat Holley 94 carb, which I now have to hand.

In a petrol powered boat fuel leaks can be dangerous so on less chance of that is good... Less "BOOM"!
The boat is only 16 feet long wooden 1930's two seater.... Some engines supplied for boats of the same size and style build in the 1930's had 95hp engines.... The high performance option was 125hp.

I might have a 1935 manifold lined up... (Thanks Brian!)

Thoughts?

Re: Do I really "need" twin carbs????
 

Need, probably not. Want, maybe. Solution, do what YOU want. I ain't real technical, but I think dual carbs look cool. Chap

Here is a pic of the truck I recently sold.

Re: Do I really "need" twin carbs????
 

If exposed and not covered by a cowl, you need three!

Re: Do I really "need" twin carbs????
 

Using a 4 bolt Merc Intake you could run a 2GC carb and be done with it. If you do go to duels, use an intake made fro racing, or a 4 bl. Just remember "Aesthetics is expensive".

Re: Do I really "need" twin carbs????
 

Yes. You're well up on compression and displacement which will really respond to better fuel distribution. Truth be told, while ultimate power will be higher the mid range control and accelleration may be easier to manage and going lean never a worry. If it were going into a car, no question. I'm not nor have ever been a boat guy so I can't suggest parameters where 2 carbs would outshine 1 as they might on the road. Yes, it's ultimately your call but those are my thoughts. Looks? We don't even need to explore that aspect, right?

Re: Do I really "need" twin carbs????
 

IIRC from my boating days, marine spec 2G's were used on the smaller sbc Mercruisers and a proper Flame Arrestor should also be available. Since it's a boat, this might be something to consider.

I agree with Ron about aesthetics.:(

Re: Do I really "need" twin carbs????
 

I may be mistaken, but i think Charlie NY advised me to run a 1 1/16 carb on my 40 over 8BA which allows you to use the loadamatic dizzy. and avoid multi carb issues.
Have the carb and will do that, but for now mine runs GR8 with Max 1 cam, Offy heads & a Carpenter 94.
Also tubman offers excellent advice as usual. Had a Gray Marine with 2gc card, bullet proof.
Have fun! m

Re: Do I really "need" twin carbs????
 

Depends on what you want to do with the boat? A lot of the 15' crackerbox race boats ran V8 60s with twin carbs in the late 1940s. Do you want to go fast and pull skiers or cruise?

Here some pictures. Look at that poor lonely carburetor, it just does not look right! One carb, "icky" Two carbs, "yummy. I especially like the boat with the two carbs and the two different woods. Its a nice theme he's got going on there. Have you considered a supercharger like in the one photo? That would get the carbs up high and out of the engine compartment. That way you could watch them for any leaks.

What do the carb floats, needle and seats do in a boat when they are getting jostled around? On my '66 Shelby GT-350, Shelby moved the fuel inlet on the Holley 4Vs from the side of the bowl to the front on the '65 and '66 GT-350s. The hard corning on the race cars was sloshing the fuel from side to side and bouncing the float up and down causing problems. Would it be better on a boat to do the same thing if your going to be out on the water spinning donuts or would it be better to hang the float from the side since the front of the boats bounces up and down. I know nothing about boats, I can't afford anymore things with engines!

Re: Do I really "need" twin carbs????
 

To give you the benefit of extensive testing, there is more performance improvement available with induction revisions than camshafts for most applications. How you get there can be through multiple carbs or 4 barrel or whatever. A stock intake with a larger carb will be an improvement but cannot match the value of a good aftermarket intake system.

Re: Do I really "need" twin carbs????
 

well said 'ole Ron bravo
Just remember "Aesthetics is expensive".

Re: Do I really "need" twin carbs????
 

When I was 16 or 17 I bought a punkin seed with a V8 60 in it.I bought it from another kid whose father saw him make one loop around the lake,then flew up onto the beach backward or sideways.It wasn't on purpose,and he made his boy sell it.I never even got to try it,after word got around what had happened I wasn't allowed to get near the water with it.

Re: Do I really "need" twin carbs????
 

I kinda side with old Ron in regards to the rochester 2G carb , a lot more flow with less drama etc .

My breakfast friends (70 plus) and I have decided " If ya cant see it at 30 mph" you are wasting your money!!!"

Re: Do I really "need" twin carbs????
 

chap52: Please replace that clear hose with high quality hose that won't get brittle and crack from today's gas and engine heat. It's a BIG fire hazard just like the old red hose "back in the 60's". Bad stuff!

Re: Do I really "need" twin carbs????
 

More carburetors, more problems.


I'm not a fan of a 4 barrel on a flathead. But I get it.

Re: Do I really "need" twin carbs????
 

Less carbs less weight too... Lol hey... It all helps get the boat on the plane.... :)

Re: Do I really "need" twin carbs????
 

The Hydro engine i built was a 258 ci and built for racing. It ran an L-100 cam and 2 04's was clocked at 62 nph in the old 1936 'Baby Ruth". But this was a race engine, it depends on the application.

Re: Do I really "need" twin carbs????
 

The 16 foot Garwood Speedster of the 1930's was very similar in layout, size and spec to my NZ build boat. They were sold with 95 hp marine engines and a 125 hp marine engine as an option and rated at 42 mph. With the Flathead Ford option which in there ads is said to have 95hp they were said to do 40mph.
In a little toothpick of a boat that sounds like plenty of speed to me with 125hp!

No towing of skiers. Just buzzing around when the water is reasonably flat.