Gas tank placement

[Moody Blu']

How does everyone feel about placing two gas tanks on both sides of the motor, near the stringers?I think GEO played with tank placement? anyone else?

My gas tank is on its last legs and I need to make it through the summer before I take the deck off.
thanks for any help.

[mattyboy]

Moody why would you want the tanks back there????
it would sink at the dock with that much weight back there.
OH boy you're gonna stur some crap up now !!!!

remember there's only one way to replace at tank eek! eek! :p

put em back there then foam the whole bilge in!!!

or are you talking about a temp solution til you pop the deck??????


Matty
where's the beer and pretzles

[FlatRacer, aka BarrelBack]

Ideally, I'd want to place the tank under the floor. Three reasons: It would lower the center of gravity which is never a bad thing in the water or on the road. It would lighten up the bow for more lift, less wetted running surface etc, which would result in more trim flexibility. It would minimize the change in C/G as you burn off fuel.
Hell, I'd put three tanks in there. One in the center and two on either side outboard of the stringers, but under the cockpit floor, not back by the engine.
You'd lose you under floor ski locker but you could stow skis and gear up under the bow.

FR :p

[MOP]

Broque I would get mail off to Geoo and Lenny, Geoo and I had a short talk on getting the weight as far aft as possible. He still did not post the New Number he turned at the 1000 Islands, I bet he wants to go even faster. But like the guys said it may screw up the balance. Its not illegal so many of the larger both gas and diesel boats I sell have the tanks inches from the engines on the outboard sides. One of my boats had aft tanks very low wedges 25 gal each, but it had a cuddy cabin so it must have balance out Ok.

[mattyboy]

Geoo's boat is a horse of a different color and has a totally differnt CG an is closer with the arny to a 22 foot boat. we are talking about A volvo boat, it doesn't need any more weight in the back, with out tabs down you'll look like the 12 O'clock show at sea world!!!!!! :rolleyes: Then I would like to hear how you mount a tank or tanks outside the stringers and where you would get such tanks???? and fuel filler system and don't forget an equalization system to keep the load even and I guess the would have to be plastic tanks cause there's to much moisture in the bilge for a alum
tank.
Flat racer any 16 or 18 I've been in has no problem getting enough bow lift

Getting the popcorn I'd Like to see this one fly

Matty
:p wink

[mattyboy]

Poodle,
lil salt on it????
just like at the movies!!! :)

Matty
keeping all the freeboard I can

[Shanghied Again]

Me and Geo just had this disgusion, I have to replace the tank in my 16. Geo said there is only one way and thats lifting the top, he did his. I will follow the advise of the Master Rigger.

[penbroke]

I had considered the same thing in desperation when I thought my tank was leaking. After looking the situation over I discovered there is quite a lot of space under the cockpit floor if you remove the storage locker. The cover still fits and it is open from the bulkhead in front of the engine forward to the bulkhead behind the original tank. I figured putting a TEMPORARY tank there would put the weight as close as possible to the original location and get me thru the season. It turned out my leak was the sight gauge so I never tried it.

Frank
Did I actually say something in a thread about fuel tanks???? eek!

[mattyboy]

Frank,
if you need any help let me know i just went thru this, is the tank the same in an OB as an i\o 16??? I used a florida marine tanks fmt-23dz original equipment on my boat.
Now I have seen my 16 and John Bencozy's OB 16(johnson 175) side by side in the water and he's got 4 more inches of freeboard so the cg on an Ob 16 is different has well.

Matty

[penbroke]

Matty,
My boat has a window in the floor that looks down on a window in the tank with a gauge like you see in portable outboard tanks. Turned out my leak was around the fitting that held the glass window for this gauge. It was soldered to the tank and the solder cracked. It had been leaking for years and had saturated the foam around the tank. A good cleaning and some epoxy sealed the leak. It took months of blowing a big window fan thru the hatch, under the floor and out under the dash to get the smell out. It now smells like "old boat" and not an explosion looking for a place to happen. :)

Thanks for the offer of help and I WILL be looking for support when I pull the deck off. The tank is clean and shiney inside so I'm hoping to put off that project for a while longer.

Frank
Can chickens really scream?

[mattyboy]

Penbroke,
I meant Frank Civitano wink but I can help you too! :D what is it with Scott's and Franks around here????? wink
Penbroke I know the site gauge I still have one plus a modern one in the dash mine was a brass cap screwed to the tanke on the old one


Matty

[penbroke]

Oops, sorry.

Frank
Reading the whole thread now, not just the last post. :rolleyes:

[knee deep]

I'd like extra butter...............

[Moody Blu']

:D thanks for all the help guys,lots of info and your all hilarious!!I figured the tanks in back would upset the balance. but it is TEMPORARY, but I like the suggestion of putting the tank in the storage locker.

Maybe ill just seal up the locker and put a gas cap on the top :p

Im going to try to filter my gas tank about 3 times and hope I can get a season out of it.I just need to find a high GPH pump so it sucks out the debris...

thanks again!!!!

[mphatc]

Moody Blu,

I'm in the same situation with my Corsican. The best location for the tank will be approximately where it presently is installed.

Why do I say approximately? All 18' hulls are simarly balanced as built, the only variations coming from the engine/outdrive weight For the sake of this conversation forget the Corsican because it has a bit higher CG, and with the seating position so close to center it's roll center must also be different.

Considering that your boat does not have power trim, and has a similar set up to most vintage 18's I'd suspect you'd probably like some more range, and a bit larger tank. When you replace your existing tank move it back just a bit, and if you want to enlarge it consider making it a bit taller.

FWIW, My Corsican with a H&M 302 and Volvo 250 and 2 adults onboard needs more bow lift on a full tank and feels "dead" until I've used 1/3 of the fuel. As best I can tell it holds only 22 gallons, so all I've trimmed is 45 lbs. Not much, but it really can be felt!
Of interest, Saturday we were 4 large adults on the boat with a full tank of fuel and the boat felt more alive than with just 2 people.

Either way you'll want it as low in the hull as possible, and the only way to get it there is a deck off winter project . . . :(


mphatc
Mario L.

[Moody Blu']

thanks mario, I plan on putting in a 40 gallon tank in fall(like the new ones have). screw the winter project. Not having a garage doesnt make that possible.
Update: I was playin around with moody today and notice my accelerator pumps are not workin, this may be only half the problem but it will help it idle right.

[FlatRacer, aka BarrelBack]

mphatc:


FWIW, My Corsican with a H&M 302 and Volvo 250 and 2 adults onboard needs more bow lift on a full tank and feels "dead" until I've used 1/3 of the fuel. As best I can tell it holds only 22 gallons, so all I've trimmed is 45 lbs. Not much, but it really can be felt!
Of interest, Saturday we were 4 large adults on the boat with a full tank of fuel and the boat felt more alive than with just 2 people.

I thought so. I still contend that moving the tank out of the bow will help top end speed because you'd be using less "up" trim on the outdrive to acheive the same attitude, and the thrust angle of the prop shaft will now be closer to horizontal, therefore the energy that was formerly spent rocking the bow up is now spent driving the boat foward.
I also stand by my statement about lowering the C/G helping in the turns.

FR :p :p :p

[Moody Blu']

thats what I thought, Hell I drive my boat with the pin all the way up right now and wish I could get more of the bow out..

hmmm...

[FlatRacer, aka BarrelBack]

Also, moving weight to the center of the boat will lower its polar moment of inertia, letting it turn quicker (like a figure skater that spins faster when she pulls in her arms). This is why real racecars are mid-engined.
While this is admittedly not so important in a sportboat, it does help when you're cranking a circle flat around a one pin turn in a river race. Hahaha! Wheeee!!!!

FR :p

[MOP]

Way back in 65 when I had my G3, which for you guys that don't know antiques was a 13 foot Glassbar. It was pushed by an 90hp Merc the further back the weight was the better it ran. Two 6 gal tanks and the engine weight keep the well 1/2 full. It was a bugger to get on plane but went like hell, when skiing I would move the tanks forward and drop two pin holes it would plane off decent but was a lot slower. Putting big guys aft is not the same as moving the CG and maintaining the same weight. Has any one tried 1/2 tank of fuel and shot bags the weight of 1/2 tank of fuel moving them aft a little at a time to see what the placement did. It may help maybe not, I do know on light outboards it seems to be the hot ticket getting the weight aft. "Please hold the salt its not good for our colesterol".

[mattyboy]

I would think if the tank needed to be moved someone racing these boat in the past would have done it ??
Mario I find the same thing in my boat I get better speed and handling with 4 adults then with 1,2 or 3. I think cause the bow is down a little. and I find my boat gets to lively when under a 1/3 of a tank so I do not want to take any weight out of the bow.
they went to 40 ( from 23 and 25) gallon tanks to increase the range of the boat and anyone who's been on the sunday run at lk george or been lost in the fog on lk george knows that 23 gallons of gas ain't enough wink
I have never seen the fuel compartment on an 18 with the deck off, the 16 is pretty tight and will probably only go to a 30 gallon custom tank or reglass all the bulkheads.
bow lift can be accomplished by prop selection or adding trim( a volvo with trim).
The key is they can be adjusted as the fuel goes by by ( and it does go by by very quickly :rolleyes: ).
Moody if you want a killer 18 you will have to travel the road CDMA took with his.
scrap the volvo go bravo and add a " stock 350"
he can also tell you about what the right prop can do.
Or you just except the fact that we have a volvo boat and 60 is our number to shoot for.

I do know someone who has the same setup ( h/m 351w volvo 250) in an 18
wonder if he gets bow lift( he has a set of wings on the deck :p wink ) perhaps some testing can be done at the lk george fall picnic wink

[Moody Blu']

I will probably keep the new tank in the general area, but I may move it back a little if that is possible. I realized that my boat is low in the water , but I have also noticed my boat has more freeboard then every 18 ive seen, jp brescia's and ss18's. maybe both of them have 40 gallon tanks?

Shooting for the magic number of sixty is a joke. Someone on this board(bzmarine) has a 80 mph volvo 250/ 351w(408ci) with a 33p prop. Dont sell yourself short matty. wink

I'm shootin for 80+

p.s.
I would never switch to a bravo cdma supposedly say they build the drives to break, well no thank you. When I get a bigger boat theyll be volvos(sx) or arnesons

[mattyboy]

who you calling short!!!!! eek! :rolleyes: :D

I don't have the need for speed Moody,
I like turn key and go and I'm sure the volvo 250 and 351w/408 are far from stock... what hull is bz pushing to 80 with that setup......

Moody, JP's boat gives the impression of less freeboard his exhaust pipes are lower bet freeboard is close to the same as yours
http://atlanticcoastdonzi.com/gallery/LG_03_Matty/9_G
http://www.donzi.net/photos/blu1.jpg

wish I had a pic of the back of JP's boat, don't look that far off to me

when you build your 80 mph 18, I still tow you in with my slow 16 wink :D

Matty

[FlatRacer, aka BarrelBack]

MadPoodle:
Except that pushing the tank back drops the stern deeper, creating more drag. These boats are a bit ass heavy anywhooo.. So wassamadda wit bein' ass-heavy???
http://www.donzi.net/photos/MsAmericaRedBank1-500.jpg

[FlatRacer, aka BarrelBack]

Not as funny as the time I watched this Garvey (Jersey shore bay racer, kinda looks like a cross between a Crackerbox and a cement trough) racer, well, let's just say he shopped at the big and tall mens store, anyway, he stepped off the dock into his boat, sat on the transom and sank the damn thing right at the ramp!!! eek!
Of course, everyone who was rolling on the ramp clutching their sides in fits of laughter jumped in to put the boat back on the trailer. We weren't completely heartless.

FR :p

[FlatRacer, aka BarrelBack]

Poodle, what's funny? That's how they sit.
http://www.donzi.net/photos/54.jpg

FR wink

[Greg K]

MadPoodle:

Some of us (to go unamed) prefer to have our boats towed by jet ski's..
Or by old men on pontoons who scream like a little girl when you give them a ride in the Donzi as payback for the tow.

[CDMA]

Wait so I say they build them to break...huh???

Chris

[mphatc]

Moody Blu,

Re-read some of this banter . . .

Having just gone through dealing with ALOT of fuel contamination problems with the original tank in my Corsican here's how I solved the problem to run for the summer . .

Bought a cheap Jabsco pump, attached my air powered drill to it and attached a line to the fuel pick up line from the tank, pumped tank dry, filtered the dirty gas, poured it back in the tank and sloshed it around, by S H A K I N G the boat with the trailer tongue / boat bow high in the air. Pump it again and repeat till fuel came as clean as could be. Using this method I removed a ton of "dirt" (~2" in a 5 gal. pail) from the tank.

Do not overspeed impeller pump, and the pump I used was not fuel compatible, the impeller swelled by the next day. But it got the job done.

My boat is set up with a large Mercruiser fuel & water separator. This functions as the main filer and now collects enough dirt to stall my boat after ~ 80-90 gallons of fuel. I bought a case of filers along with a container to store one dirty fuel filter on board. I carry two extra filters, and can change them practically on the fly . . . . :D Filter expense has been a more than desired, :( but atlweast I have been able to use the boat!!! :) :)

Work in open space and a well ventilated area, keep all electrical stuff away, and disconnect you boat battery. There will be alot of fuel fumes, and I advise lots of caution!!!!

POst me directly or call me at work if you'd like further information on this.

mphatc
Mario L.

[Moody Blu']

mario, I did that last summer and it worked out well.
cdma, Yea you did.... happy_bi
matty, hes got a 18' classic and its turn key as well(its just stroked)

UPDATE: I tore my carb apart at work today and HOLY s#*t it was a F#*^in MESS!!!! I have never seen such junk in a carb. None the less I dropped everything in the chemical parts cleaner and the carb body and all the parts look brand new. :D

I had no clue it would be as dirty as it was.I had played with the seconday mains right before the end of the season and the inside of the carb was spotless, and now this???? I couldnt believe it. the summer before I didnt even touch the carb and when I changed the secondary jets it was, like i said spotless. Well I learned a lesson, TAKE THE CARB OFF at the end of every season. wink

[mattyboy]

DO NOT USE DRILL DRIVEN PUMPS FOR ANYTHING FLAMABLE THAT'S HOW THE PAINT SHOP IN LOWER MANHATTAN BLEW UP A YEAR OR SO AGO THEY HEAT UP AND GO BOOOOM!!!!

PLEASE we want you guys around!!!!
to drain the tank connect to the fuel line going to the engine might need to make an adaptor then use a hand pump to start a cyphon then just have gas tanks on ( I used a tube going right out the bilge plug hole) hand to catch the gas

Matty

[mattyboy]

BTW if you want to see something with no freeboard you gotta see my fat ass on a jet ski!!!!!! eek! :rolleyes: :p :D

Matty
let me show you some of the moves that make me famous!!!! :p

[GEOO]

Broque,
What size tank do you have now? 25 or 40 (+-).
I like having the tank, battery and other heavy weight deep in the center of the hull. I also like having the gas tank near the Balance point from bow to stern. Then an empty or full tank won't throw off the balance. I think most of the 18 have the tank a little too far foward. But be carefull, the more you move the weight back, the more porpusing you will have at slower speeds. But after saying that, if you want to go fast, the less outdrive trim you need to carry the bow (ie move weight back), the faster you will go. Run with light fuel and put a sand bag on either side of the engine at the stern see what happens.
My tank is in the stock location but pushed back. It starts at the front of the rear seat and goes 72" foward (62gals). The boat ran faster with 60 gals of fuel this year then last year with 40 gals. I also added more weight to the rear of the boat (two more trim pumps, Larger oil cooler, water injection system, tank, pump, plumbing, bunch more wires.. etc approx. 100lbs.) The boat is harder to get on plane and porposes at slow speeds, but carries the bow much better.

[FlatRacer, aka BarrelBack]

What did I tell ya? That Geoo's one smart cookie.
:p :p :p :p :p :p :D

[oldLenny]

George, between the added weight (approx 100 lbs) and the Arneson, do you think you are now at the stock weight of the Alpha or Volvo outdrive hanging off the back?

As well, you note that the boat runs faster with this 220 EXTRA pounds of fuel in a more rearward position. Do you think that it would "plane" easier in this current configuration if it had an outdrive? (obviously with a lot of tradeoffs in performance)...

[GEOO]

Lenny,
I run a 14" dia. prop. When I put on a 15", she jumps right out of the water, but doesn't handle as well at high speeds. I think my engine (block 20 lbs heavier), MPI, Blower, Intercooler, Oil Coolers, Pumps, Drive, Rams, ect. weigh approx 200 lbs more then a 350ci Bravo set up.

[JP BRESCIA]

I often monitor the site but hardly reply. Being that my name was mentioned I may as well jump in. I always wondered why my exhaust is 1/3 underwater. Compared to other 18's it appears that my holes are lower down the transom. Can anyone tell me why this may be? Freeboard also seems to be a little bit lower than other 18's. Probably the added weight of the original log type exhaust. Since my boat is a 1980, Donzi should have known how the boat sits and I can't imagine a builder wanting the exhaust tips 1/3 underwater. Chisolm factor???? Any info from the historians would be appreciated. Thanks. Also, my wife and I recently had a new baby boy. I am seriously looking at a 20' Edgewater with a 22 Classic a close second. Depends on convincing my father to but the Edgewater and I'll buy the 22. We'll see. In anycase, I am going to seriously list my 18 for sale. All prior attempts were half hearted. Sorry to the guys who were interested for not sending pics. Like I said, it was a half hearted attempt and this was the only place I mentioned or listed it for sale. However, the 18 is now seriously for sale (or trade consideration) wink

[JP BRESCIA]

I often monitor the site but hardly reply. Being that my name was mentioned I may as well jump in. I always wondered why my exhaust is 1/3 underwater. Compared to other 18's it appears that my holes are lower down the transom. Can anyone tell me why this may be? Freeboard also seems to be a little bit lower than other 18's. Probably the added weight of the original log type exhaust. Since my boat is a 1980, Donzi should have known how the boat sits and I can't imagine a builder wanting the exhaust tips 1/3 underwater. Chisolm factor???? Any info from the historians would be appreciated. Thanks. Also, my wife and I recently had a new baby boy. I am seriously looking at a 20' Edgewater with a 22 Classic a close second. Depends on convincing my father to but the Edgewater and I'll buy the 22. We'll see. In anycase, I am going to seriously list my 18 for sale. All prior attempts were half hearted. Sorry to the guys who were interested for not sending pics. Like I said, it was a half hearted attempt and this was the only place I mentioned or listed it for sale. However, the 18 is now seriously for sale (or trade consideration) wink

[Moody Blu']

Geo I have the 25 gallon tank in my boat.
I definately feel from the atitude of my boat EVEN with THE PIN UP ALL THE WAY, there is definately some weight that needs to be pushed towards the aft.

Ever hit a wake of one of those 50' plus boats
Smack right in the middle of the hull everytime!! Unless you launch it and land smooth or bounce over the tops.. wink

I think if the weight was pushed back a bit it wouldnt smack as hard and perhaps not give the rider that JOLT you get from smacking the wave of a 50' boat.(theory: it would cut more into the wave instead of smackin it).

On the other end of this theory it could perhaps slow the boat down in rough conditions?

I say this because i have seen a couple boats that I know were faster then mine get passed by mine in rough water. Why? there boats were to busy bouncing over the waves then skimming over..

does that make any sense?

On a side note.

Anyone know where I could get a steel ball for my edelbrock carb(carter afb)? the ball that goes into the accelerater pump housing? The bal I have was STUCK in the hole that it closes off(corroded) and i cleaned the ball but it has pitted and I dont want to use it. I tried a auto parts store but no luck...

[Moody Blu']

by the way, this thread has a feeling of the old days, but is missin a couple heads.. wink