Help me pick a hull for a OMC V-8 looper........

[Instigator]

Great point Matt.

Will add that to the equation.

Was just remembering that that the 8’s being bridgeports like the first 2.7 V-6 I built way back when...,I calculated surface area of the two bridges exhaust ports compared to the single oval port that replaced them, stock to stock, the bridgeport’s had 33% more port area ��

I just measured the ones in my 8 are at 1.785” so I’ve got some whittlin to do.

Gary I think this has been touched on but a key part of the hull choice will be what kind of range you want from the boat. The V8 thirst is legendary. As an example, Kevin suggested a Triad V21. They are great boats and a few people have put V8s on them. But, they have a fuel tank that’s something like 28 gallons (I’ve forgotten exactly). Even with a 3.0 OMC I found this pretty small and would haul around jerry cans often (you can wedge them in the storage areas right up against the transom).
My Scarab that is being prepped for a V8 will have an 80 gallon belly tank so I can actually get somewhere if I want to.

Matt

[FUJIMO]

Gary I think this has been touched on but a key part of the hull choice will be what kind of range you want from the boat. The V8 thirst is legendary. As an example, Kevin suggested a Triad V21. They are great boats and a few people have put V8s on them. But, they have a fuel tank that’s something like 28 gallons (I’ve forgotten exactly). Even with a 3.0 OMC I found this pretty small and would haul around jerry cans often (you can wedge them in the storage areas right up against the transom).
My Scarab that is being prepped for a V8 will have an 80 gallon belly tank so I can actually get somewhere if I want to.

Matt

...man, you sure you want to bring up fuel tank sizes, for a prospective boat, for this project? You can get your head chewed off for that here. I did.

[Instigator]

Funny thing is, (that wasn’t me BTW ��) is Ive talked to several w/history running 8’s and I think if tuned, propped, set up right, they’re not as bad as people think.

Does it burn more than a V-6 looper?
You mean one that’s 75 HP down on the 8....?

Thats 33.3% more HPs.
That power consumes fuel to be created right?
33.3% more fuel than a 6?
Probably.

I think w/the late era mid bores and a strong ignition, you might do OK.

Besides it’s about the howl not the economy ��

...man, you sure you want to bring up fuel tank sizes, for a prospective boat, for this project? You can get your head chewed off for that here. I did.

[tunnelfun]

The 23 Daytona stock 300 V/8 got 2.6 mpg at 100 MPH, and most other on plane speeds. With the stock 300 Promax it got 3.2 MPG at 100 MPH, and most other on plane speeds. The big difference was acceleration. With the same prop and load the V/8 wins by many boats in the standing 1/4.
The stock 1980 Merc 142 cubic inch 200 carb motor got 4.2 MPG at 80 MPH (one person, 20 pound battery, no gas, no cooler, no nothing), and as low as 3.0 MPG at 25 MPH. Need to run into the wind to get past 60 with the 200. After that you can turn around and go any direction you want at 80.
A pair of 24 gallon transom tanks was the hot setup. The single motor 23 don't like saddle tanks.

[MattGreen]

It’s all good - in the scheme of things, Merc/OMC/Yam, gas/diesel, OB/stern-drive...boats burn lots of gas....gotta pay to play...I actually feel good about putting $200+ worth of gas in my boat - it means I’m using it lol !! Short season up here ha ha. I think Gary grew up with crossflow V6s - a V8 is probably not much worse than a TwoThirstyFive

Matt

[FUJIMO]

The 23 Daytona stock 300 V/8 got 2.6 mpg at 100 MPH, and most other on plane speeds. With the stock 300 Promax it got 3.2 MPG at 100 MPH, and most other on plane speeds. The big difference was acceleration. With the same prop and load the V/8 wins by many boats in the standing 1/4.
The stock 1980 Merc 142 cubic inch 200 carb motor got 4.2 MPG at 80 MPH (one person, 20 pound battery, no gas, no cooler, no nothing), and as low as 3.0 MPG at 25 MPH. Need to run into the wind to get past 60 with the 200. After that you can turn around and go any direction you want at 80.
A pair of 24 gallon transom tanks was the hot setup. The single motor 23 don't like saddle tanks.

...so the winner is a V8 at 2.6 m.p.g. going 100 m.p.h., with dual 24 gallon tanks. sounds like a plan.

[mrichartz]

If your starting with an old school V8 gas mpg is not your first concern..
But Sounds right.. I don't think(could be wrong) this is for long cruising it more the setup..
The loud V8 on a classic boat for having fun ripping around in a mix of water conditions? Making a statement..old school!!
This isn't about mpg as much smiles per ...
And cruising distance going to carry more fuel/weight going to take away from it.. need enough fuel to get to the next gas dock. Lol.

2.6 gals vs which motor mpg 4?

[Instigator]

No doubt.

Im way good w/that.

My friend w/the 8 on the 22 Talon runs for miles at a time w/it on the Ohio River.
Is a killer river boat.

...so the winner is a V8 at 2.6 m.p.g. going 100 m.p.h., with dual 24 gallon tanks. sounds like a plan.

[tunnelfun]

Let's take a little harder look at the situation. What boats will sit at 100 MPH for 100 miles in reasonable water without blowing up or wrecking, and what do they cost?
18 to 20 foot puddle jumpers with 2.5's won't so they're out.
Big supercharged outdrives will do it a few times before they blow, maybe. So they're out.
So you 're left with big turbines and big diesels. How many of those will you ever have to deal with? Don't leave much does it?
What's left is mid size tunnels with big block outboard power standing king of the hill at the top of the pack.
Hey guys, lets take a nice long high speed cruise up the river. No, no body? You guys just gonna sit here on the beach talking about top speed and drinking beer all day?
OK, gotta go have some serious fun. See you later.
I know it's different than 0 to 120 for a few seconds, been there done that, it was fun. But once I started high speed cruising I never looked back. I wish everyone could try it at least once.

[baja200merk]

I’ve seen many 2.5s do 100+ mile runs at 100. Run after run big prop is key but literally cruise around 100. Palatka we do 100 miles a day for lunch still plenty of time for beer when we get back to the pool at the hotel.

7mpg at 90 is 4800ish how far u wanna go I got 28 gals and cup holders

[mrichartz]

Damn now 7 mpg at 90 that's impressive

[tunnelfun]

I lived in Tampa Florida for ten years. Don't remember seeing any 18/20 boats running 100 in 2 foot on ST Johns. It's a very nice river for little boats, rarely caught any rough water there the times I used it. Saw two foot once, no little boats out. Perfect for my 21 Daytona v-drive, should have kept that one. The Potomac and Mississippi are a different thing. Nothing under 22 lives at 80 on those rivers for very long. Lot's of people tore up a lot of little 2.5 boats on those rivers trying to run with me. The mid size twin 2.5s that did keep up burned through a lot of rings.
Never seen a 18 or 20 foot single 2.5 that could run 100 with me in 2 foot chop. Nor would I want my friends to try. I like my friends, want to keep them. Not bury them. Does any 18/20 run 80/100 in two foot chop?
My point is the big modified V/8 on a mid cat can do something few other boats can do. And still pull hard on the way to 110 plus.
Now that Mercury thinks we "will, need to, should, might pay" $30K + ????? for big motors to push bigger boats the hot rodded V/8 will finally have some competition. But with the weight of the new Merc will it, really?

[baja200merk]

2ft? It’s a 500lb boat I won’t even put it in the water. Yea I got ya there is no Swiss Army knife of boats the wicked and lcb are as close as you can get to one. Flats deck 100+mph trolling motor spinning on the bow and 2 ff wouldn’t be a problem single 300.

300r is not heavy it will go faster than the 300x that’s been proven.

[Instigator]

BTW, I weighed the air box just before throwing it in the trash.
13 lbs!

So the 550 lb pig is now 537 ��

[mrichartz]

V8 airbox weights 13lbs? Damn just put it on a diet can loose how much?