is my gas tank too small for a V8????

[pmjr0987]

Just got a 1985 fourwinns horizon cubby 19.5 for a steal $$

Doing some work on it I took up the screwed on piece of the floor above the gas tank to see rot (not bad at all) and peeped the tanks specs on the tank

Its a 27 gallon gas tank with a mercruiser 260 5.7 V8 and alpha one.

How many gph is this thing going to use? I keep reading 7-8 gph which is like 3 hours cruising pace and I'm looking at maybe an hour max of wot full to empty?!!!

That just seems extremely small for the fuel needs of a v8

So my question is what does a 2500# boat with a v8 use for gph at cruise (I see maybe 3200 rpm) and wot ?

I can't see them selling a single one of these boats if they can't go more than 90 miles full to empty... And forget about it if you decide to go wot for a bit

 

[Texasmark]

Rule of thumb the guys in the business who write on here say 10% of your hp in gallons per hour. I know that's vague considering all the variables possible in rigs but it's a number. The number means the hp you are using. So figuring 20 gph for a 200 hp engine you need to be at WOT. Obviously if you are just trolling, and only using 20 hp it's more like 2 gph.

 

[Scott Danforth]

My searay had only 37 gallon tank. I could do about 100 miles of cruising at 30mph, or about 50miles at wot (50mph)

A 27 gallon tank may be fine. Depends on your application of the right hand on the throttle.

 

[thumpar]

It seems kind of small for that size boat/engine but not terrible. Mine is a 40 and have learned to lay off the throttle so save on fuel.

 

[H20Rat]

that is pretty typical...

 

[Lowlysubaruguy]

Actually if you have a standard boating ritual the smaller the better with our current fuels. Ethanol based fuels go bad fast. I have a 40 gallon tank with a 4.3 my boat is efficient and unless Im skiiing or tubing people all day I would have a hard time running a tank out in a day and my boat is not moored so I can fill it daily if we are using it a lot. So my real concern is fuel gauge accuracy.

Now if I went off shore chasing Tuna or something like this id want a larger tank but a lake boat or something thats not going more than a few miles off shore your probably perfect.

Late in the season I try to run my boat bone dry if at all possible I will have my trolling motor on back and will actually run it out. I have found empty is better than any fuel unless im running non ethanol when i put it away for the winter. Its hard to run it empty because the last week or two of the season are always complicated.

 

[bruceb58]

That's pretty small. My 20' cuddy with a 5.0L had a 50 gallon tank in it.

 

[cptrick3]

Seems like a lot of motor for a 27 gal tank. Do you have room to add a second tank?

 

[smokeonthewater]

Your numbers are right and not uncommon at all... Yeah it's on the small side but it is what it is... If you are running full throttle you need to fill up every couple hours....

The part that would worry me though is the rot you mentioned....

 

[tpenfield]

The tank and the engine seem to be a mis-match. Makes me wonder if there was a 3.0 or a 4.3 in the boat originally :noidea:

 

[pmjr0987]

OK pretty much the responses what I thought lol. I guess back 30 years ago some things just weren't packaged well

Its going to be a river boat... Normally run up and down the Hudson river either tubing or waterskiing. I'm going to add a outboard mount on the swim platform to mount my 5hp Nissan when fishing to save gas

River does get some big waves when its windy and I had a 16' bayliner bowrider that I loved running but it was just too small for the river. That boat with an 85hp force would go all day on 12 gallons of gas... Mix of trolling and cruising

The rot is not much of rot, the boat has wooden 1x4's over the gas tank that have no coverage and when I took the carpeted cover off I saw the edge of the wood was a little soft .. Plywood and anything that's fiberglassed feels very solid. Impressive for a 30 year old boat

 

[bobdec]

I boated the lower Hudson NYC to Newburgh-Beacon Bridge for about 10 years, started in a 19 ft cutty I/O and went to a 26 ft inboard cruiser both had 5.7 L GM engines about same HP as yours. With water conditions plus the commercial tanker/cargo and day cruise traffic you probably already know there are not to many "flat as glass" days you can run a 19 footer at WOT. Plus at WOT 40 MPH+ you can see the whole lower Hudson round trip NYC to Newburgh trip in less than 3 hours. My guess most all of your cruising will be at 2500-3000 RPM below 7 gal/hr. And that 5.7 will run all day at a nice scenic 1000 RPM sightseeing cruise. If you get into the water sport tubes and boards outings then stay close to fueling locations.

 

[JaCrispy]

My 22' has a 45 gal tank. Like others said, the more you hammer down alot more gas you burn. It's 14 miles (prob 5 miles no wake) to my fishing spot where I usually drift, but do troll sometimes. I can do that day trip and only burn 1/4 to 1/3rd tank. But ripping around more like 1/2 tank. Just plan on filling up every time you go out.

 

[UncleWillie]

My 4.3 with a 27 gal tank, uses 16gph wide open , with an average seasonal usage of just under 4gph including a lot of water sports. Tubing, Skiing.
You could empty your tank in less than 90 uncomfortable minutes, no problem. But 5 hours will be more reasonable.
Add a couple of hours just drifting/anchoring and you are looking at a very long exhausting day on the water.
At no wake, idle speed expect to use ~1 gph.

It is a Day Boat, You'll have enough gas to go all day, and travel 100+ miles at a ~25mph Cruise Speed.

 

[smokeonthewater]

Actually if those figures are right, 75 miles max since you need a reserve of fuel....
At 25mph that's 3 hours.

 

[pmjr0987]

OK so there is hope... I have a seadoo XP and can empty the gas tank (16 gallons) in less than two hours having fun... So when I saw the v8 and saw the tank size it kind of freaked me out a bit but this boat will be trailered every time and fueled up before each outing.

With my 85hp outboard 16' bayliner the 12 gallons would last a few hours on the water. Shoot 75 miles is plenty, that would put me in NYC from where I put my boat in the Hudson so that's reassuring! If I decide to take it for a trip there are fuel stops all over the Hudson but at roughly $1 more a gallon than on the streets

I suppose fuel won't be so much of an issue than, most likely I'll take the boat out 1 or two times a month for a few hours each time... Many hours will be relaxing with the anchor out anyway

 

[smokeonthewater]

There ya go... my 30'er has a 115 gallon tank and can empty it in 2 hours but I seldom use more than 25 gallons in an outing and often less than 10 tho I scarcely get out of sight of the dock with that.

 

[H20Rat]

OK so there is hope... I have a seadoo XP and can empty the gas tank (16 gallons) in less than two hours having fun...

Its actually worse than that! The biggest xp tank ever fitted was in 2000, at 14 gallons. The 947's will suck up 14.8 gallons per hour a WOT. So if you really tried, you could empty that tank in under and hour.

 

[pmjr0987]

Its actually worse than that! The biggest xp tank ever fitted was in 2000, at 14 gallons. The 947's will suck up 14.8 gallons per hour a WOT. So if you really tried, you could empty that tank in under and hour.

Mine is a 2000 I thought it was 16, guess I was a tad off, regardless yea its extremely thirsty two stroke she lives in the 6,000 rpm range all day. So we each take a 15-20 minute turn on it and that's about it lol


I was able to take the boat out a few times and I had it out for 5 hours, about half that time was sitting anchored and I ran through 20 gallons. Total of about 15 minutes wot in that time and cruising was 3,000 rpm around 28-30mph. Not as bad as I thought, though next time I go out I'll be doing some tubing and water skiing so I think I will have to fill up once on the water