another estimate of fuel usage.

viper1

Petty Officer 1st Class
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Well seems to be a popular opinion. Guess the water will have the final say.
 

UncleWillie

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A 3.0 Merc. cruse in a 221 Islander Hard top. Prop approx 22 pitch. Says it will run at 35 or so with 4 men and gear.

If the "Or So" part means more like a little over 40mph then the 22 pitch is the correct choice.
However it is highly questionable that a 3L engine will push a loaded 22 ft. boat over 40mph.

35mph maybe, maybe less, but the engine would be lugging at under 4000rpm or the prop would have over 25% slip.
Either the numbers are wrong or the set up is wrong.

Agreed Conclusion: Something is Wrong!
 

frantically relaxing

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One important piece of data that I didn't see (or missed) is the fact that most 3.0's are running a 2:1 gear ratio, not the higher ratio's everyone else is used to. So a 20-something prop isn't necessarily too much. FWIW, my little 17' Bayliner with 7 adults, a 21" prop, and 4400' altitude would plane out in less than 5 seconds and hit about 43mph. (with just me planing was almost instant and would hit 48mph on a good day)

That 21'er will be heavier, but with some extra air to breathe in (lower altitude) to compensate, 35mph in a 21'er doesn't seem all that "not right" to me. Those little 4 bangers have more grunt than most people give them credit for. They're biggest power problem is lack of high rpm power.

As for gas mileage, I routinely got better than 6 mpg out of ours when cruising at around 23 mph...
 
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viper1

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thats a a welcome thing to hear. I haven't found a lot of data on this boat or engine.
 

oldjeep

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Just a couple thoughts here. An islander 221 is a very light boat that weighs somewhere in the neighbor hood of 2000-2500lbs - so basically lighter than a 19ft glass runabout. Pretty easy to believe that it'll do 35-40 MPH with a full load, my old bayliner 195 with the 3.0L did 43MPH with a 21 pitch prop.
 

Brian 26

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According to owner. He opens up till its on plane, which he says is quickly. Then backs off to any where between 20-25 . Claims he got 4 day trips, out 13 mile and trolled 4-5 hours and back on less then 40 gal. Not sure what that would come out to though.


Assuming he is trolling at 3mph that is 158 miles. Divided by 39 gallons of gas = 4.05mpg

26 round trip miles x 4 days = 104
4.5 hours trolling @ 3mph x 4 days = 54 miles
​104+54 = 158

I'd be surprised if that carburated motor was doing that well. Just guessing from experience I would think that boat would be in the 2-3mpg range. Better if it Fuel Injected.
 

UncleWillie

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BoatTest shows a modern 18ft Glass BowRider with a 3L engine loaded to 2800lbs...
Idles at 3.2mph at 0.5gph./6.4mpg
Cruises at 27mph at 5.8gph/4.8mpg
Tops out at 40mph at 10.5gph/3.8mpg

Using these numbers.
104 mile Cruise = 104/4.8 = 21.6gal
104 mile WOT = 104/3.8 = 27.4gal
18 hours Trolling = 18 x 0.5 = 9.0gal This is assuming 4 to 5hrs Trolling per day, not 4 to 5hr total.

Equals 30.6gal, Cruise and Troll
Equals 36.4gal, WOT and Troll.

An older Carbed engine in a 22ft light-weight boat using <40 gals is not completely out of line.
 

viper1

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Well at that rate i definitely will be a happy camper. Can't wait to try.
 

Mischief Managed

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Assuming he is trolling at 3mph that is 158 miles. Divided by 39 gallons of gas = 4.05mpg

26 round trip miles x 4 days = 104
4.5 hours trolling @ 3mph x 4 days = 54 miles
​104+54 = 158

I'd be surprised if that carburated motor was doing that well. Just guessing from experience I would think that boat would be in the 2-3mpg range. Better if it Fuel Injected.

Typical (open loop) fuel injected marine engines and carbureted marine engines have very similar fuel consumption per HP. Fuel injection can improve fuel economy nicely on a closed loop engine, but those are still pretty rare in the marine world.
 

thumpar

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The numbers still don't work. Unless you can get it to recommended full WOT you are just hurting the engine.
 

oldjeep

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The numbers still don't work. Unless you can get it to recommended full WOT you are just hurting the engine.

Curious why you think that it won't get to WOT? A 3.0L in a light boat is plenty capable of hitting WOT with a 21/22 pitch prop on it.
 

achris

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Curious why you think that it won't get to WOT? A 3.0L in a light boat is plenty capable of hitting WOT with a 21/22 pitch prop on it.

Because with a 22" prop, a 1.98:1 drive and the owner saying it gets 35mph, that will mean the engine is only doing about 4000prm.... Those numbers come from a prop calculator.... If it's hitting the proper WOT revs with a 22" prop it will be doing in excess of 43mph....

That from a 140hp in a 22 foot boat? Not a chance! The first engine in my 20 footer was an in-line 6 (Mercruiser 165), and with the right prop, (17"), and light loaded, I was only just touching 34mph.... So, the owner would have us believe that 2 cylinders and 25 horsepower less will push a bigger boat faster....

2 expressions come to mind.... "Pull the other one, it plays Jiggle Bells", and "Who do you think you're kidding?"

Chris.........
 

oldjeep

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Well. in a Bayliner 195 which weighs more than the boat he is looking at you can do 43+ with a 21 pitch prop and a 3.0L. The fact that the previous owner says it only goes 35MPH flat out could just mean that he doesn't know how to operate the trim.
 

achris

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Well. in a Bayliner 195 which weighs more than the boat he is looking at you can do 43+ with a 21 pitch prop and a 3.0L. The fact that the previous owner says it only goes 35MPH flat out could just mean that he doesn't know how to operate the trim.

Doesn't alter the fact that 35mph WOT, 22" prop and a 1.98:1 drive means the engine is seriously overloaded!
 

smokeonthewater

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personally I think this discussion has reached the end of any useful info until the boat has been sea trialed......

Once we have real world data we can go further.... there are plenty of variables..... ex what if the prop was re-pitched, OR the coupler or hub was slipping OR the prop was blowing out OR OR OR....

Let's get some numbers and go from there.
 

viper1

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Well actually i said mine would do around 30 or so and he said his loaded with 4 guys and gear would go 40 or so. He really didn't pin it down as my question was how good this boat got on plane. He said easy as it go's 40 or so but i never run her WOT. He said he gets it on plane and pulls back to cruise slower to save fuel. He was a timid but trust worthy type. So i'm thinking he seen 40 one time and backed off. That's why i asked. Mine would do 30-35 on smooth water with me or maybe another person. It also had this engine. But i didn't play with pitch of prop. I know he did. And he has a marina do all his work also. So it might be stupid of me. But thinking a marina would know that.
 

thumpar

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It doesn't matter if it was run at WOT or not. It still needs to get there. Even at cruise speed if it is overpropped it will damage the engine. Get it on the water and see what it will do.
 

airshot

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Perhaps I can shed some light here as I own the same boat, 22' Islander with carbed 140hp. I have a 19" pitch....yep tried a 22 and way to much, only about 38-4000rpm. Now in the real world I can run 34 mph with GPS in mild seas @ 4500 rpm, with two full size adults and fishing gear including a 9.9 kicker and 25 gallons of fuel. My avg fuel economy is at around 3200-3400 rpm depending on sea conditions and avg around 4-5 mpg, have done higher in really flat seas. At 4000 rpm that drops to about 2- 2.5 mpg. Either someone has the wrong numbers or mabey he has the wrong outdrive gear on his boat..
 

viper1

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Well I need to look at this to see the hp. Ive seen these rated from 140 to 190 HP I believe the one i sold say 185 HP. If there truly is different HP and they very well could be. depending on carburation and other things. It could be why so many different opinions. Wont know till it hits water in May. But i will see if the HP rating is there.
 
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