Fuel consumption compared to HP and distance traveled

[Home Cookin']

Re: Fuel consumption compared to HP and distance traveled

... One thing that threw me though is that is reading reviews by owners many said that one of the downsides of the boat is that it can only be used in salt water. Do you have any idea why you cannot use any boat anywhere you want where safety permits?
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this is why you don't believe everything..maybe anything...you read on the internet. That statement is nothing but wrong. In fact I'd say it ranks up there with one of the dumbest I have seen when it comes to boats. And "many" said it? Scary.

 

[Texasmark]

Re: Fuel consumption compared to HP and distance traveled

One thing we may have missed in this is the actual HP required for a given situation. If it takes X hp to maintain a certain spot in the performance algorithm under a fixed set of conditions with a specific boat, and we have an engine running at WOT to satisfy the requirement as compared to a larger engine running at a reduced throttle yet maintaining the same performance, the latter is running more efficiently, regardless of the peculiarities of the specific engine designs, given apples and apples. Data curves abound attesting to this fact.

Besides, as others have said: If a storm is coming your way the larger engine would be your safest if you were able to use the added hp to your advantage.

Mark

 

[Outsider]

Re: Fuel consumption compared to HP and distance traveled

I'm not sure I've ever owned a boat that was over-powered if at or under the maximum rating. I, too, have long been a proponent of at least 75% of maximum hp rating. Haven't shopped boats in awhile, but one hp rating under-power seemed to be the norm when sitting on the dealer lot ...

 

[Texasmark]

Re: Fuel consumption compared to HP and distance traveled

I'm not sure I've ever owned a boat that was over-powered if at or under the maximum rating. I, too, have long been a proponent of at least 75% of maximum hp rating. Haven't shopped boats in awhile, but one hp rating under-power seemed to be the norm when sitting on the dealer lot ...

My guess is that it reduces the cost and helps to move the sale.

Mark

 

[Home Cookin']

Re: Fuel consumption compared to HP and distance traveled

Overpowered at rating:
At my hunt club, we put a 25 on a 14' jon and considered it overpowered even though within the plate, so we went down to 15. With a load it was fine. With an adult, experienced boater, paying attention, it was scary fast but fun, and fine. But for the rest of the club, including the young teenagers, it was extremely dangerous. 15 served all uses well and kept it in control.

 

[Texasmark]

Re: Fuel consumption compared to HP and distance traveled

Overpowered at rating:
At my hunt club, we put a 25 on a 14' jon and considered it overpowered even though within the plate, so we went down to 15. With a load it was fine. With an adult, experienced boater, paying attention, it was scary fast but fun, and fine. But for the rest of the club, including the young teenagers, it was extremely dangerous. 15 served all uses well and kept it in control.

Well sir, a lot of the BIA cert is based upon dimensions. Case in point is my current 17.5 ft alum bass boat with a wide beam rated for 130 hp. The boat weighs about 7-800# and the bow has a really high rake meaning that you have to get 3' back into the hull before you have any depth. In addition, being tin, the bottom is one dimension, but the gunwale is 6" to each side wider. But it meets the L x W criteria. I have run this boat at 50 mph, check my avatar, with my stock 90 '02 Merc. I can't imagine what the 130 would do and at 70+ years of age, I don't need to find out.

Mark

 

[Home Cookin']

Re: Fuel consumption compared to HP and distance traveled

Also on smaller boats you get a higher HP rating if you have a console (or maybe a lower one without it--same difference). The lxw formula is but one factor.

 

[Texasmark]

Re: Fuel consumption compared to HP and distance traveled

Overpowered at rating:
At my hunt club, we put a 25 on a 14' jon and considered it overpowered even though within the plate, so we went down to 15. With a load it was fine. With an adult, experienced boater, paying attention, it was scary fast but fun, and fine. But for the rest of the club, including the young teenagers, it was extremely dangerous. 15 served all uses well and kept it in control.

As I said before sir, everything is a compromise. Obviously compromises come in different colors and flavors.

Mark

 

[bonz_d]

Re: Fuel consumption compared to HP and distance traveled

On a new to me Aluminum 16' it is rated @ 70hp max and has a destroyed 70hp VRO on it. The boat dry is stated to weight about 550lbs. I've looked at it this way. While the boat is rated for that size engine it is more engine than I need. Why do I think this? One because most all of the waters it will be used on are 1000 acres or less. Two, many of the areas I fish are in very shallow and protected areas. Three, top end is not as important as what the boat will draft while trolling or drifting.

As for now I've found a 50hp looper which is roughly 60lbs lighter than the 70hp which should lower what the boat will draft yet still provide about equal performance with the right prop. At the same time I'm also keeping an eye open for a 60hp 2 cylinder looper which will improve performance over the 50hp yet it still weighs the same.

So does this thinking follow the topic? In this case I don't see were there would be much difference in fuel usage with either of the three combinations.

 

[Home Cookin']

Re: Fuel consumption compared to HP and distance traveled

unless you were comparing three engines that cost exactly the same, fuel savings is seldom relevant, mathematically, to the decision of which engine to buy in that size range.

 

[bonz_d]

Re: Fuel consumption compared to HP and distance traveled

unless you were comparing three engines that cost exactly the same,

Why do you say that? Haven't even considered the purchase price. Though I figure all would be in about the same price range. Give or take a couple hundred bucks depending on condition. Quess I'm looking at it more from a hp to weight ratio than fuel usage.

 

[gilcarleton]

Re: Fuel consumption compared to HP and distance traveled

The reason for my original post was because I was looking at a used boat with a 200 hp engine. That boat was sold before I could purchase it but I have learned a great deal from this discussion. The true question I was pondering, and the reason for my post was that if you are going to drive an automobile 100 miles, you would burn more gas if you were driving a 427 Chevrolet than the same car with a 6 cyl. If you drove the same speed, you would still burn much more fuel in the 427. Since I fish and usually just drive to where I want to fish and turn the engine off, I wondered if the extra speed would from the 200 hp would equal things out on the water. There are many more dynamics in play on the water than driving down a road. The size, weight and design of the boat all contribute to fuel economy. Since I am retired I would prefer to go a little slower if necessary but be able to afford to fish everyday. I have come to believe that there is no easy answer to this question.

 

[bonz_d]

Re: Fuel consumption compared to HP and distance traveled

gilcarleton, just like an auto there are things that can be done to improve fuel usage. Like keeping the engine tuned, Keeping the bottom clean, keeping the boat properly trimed. Running thhe right prop, driving habits and many others.

Also an I/O 4 stoke normally gets better fuel economy than an older 2 stroke of the same size.

 

[Charlie in TX]

Re: Fuel consumption compared to HP and distance traveled

gil, I have a problem with your analogy. If the 427 and the 6 cyl are in the same car/truck, they will get very close to the same mileage. I went to Fuel Economy and looked up my Ram 1500. Mine with a 5.7l is rated at 14C/20H. The same truck with a 3.7l is rated at 14C/20H. No difference for the bigger motor.

Why is that? It is about energy needed to maintain a speed vs how efficiently a motor can make that power.

Another example, I have a McKee Craft 18 with a 90hp Johnson. There is another identical boat where I fish with a 140hp Johnson. If we are going about 20-25 mph, we will burn about the same amount of fuel. If we go 30 (wot for me), I will burn more. If he goes wot, his fuel economy will drop to about what mine is but he will be going 45.

 

[bonz_d]

Re: Fuel consumption compared to HP and distance traveled

Another example, I have a McKee Craft 18 with a 90hp Johnson. There is another identical boat where I fish with a 140hp Johnson. If we are going about 20-25 mph, we will burn about the same amount of fuel. If we go 30 (wot for me), I will burn more. If he goes wot, his fuel economy will drop to about what mine is but he will be going 45.

So in essance at WOT using the same amount of fuel in one hours time your friend will be 15 miles farther up river than you. So actually are you not using more fuel to go the same distance?

 

[H20Rat]

Re: Fuel consumption compared to HP and distance traveled

So in essance at WOT using the same amount of fuel in one hours time your friend will be 15 miles farther up river than you. So actually are you not using more fuel to go the same distance?

Better yet, he is using less fuel to go the same distance. If you are talking 2 engines, both running at WOT, the slower one that will GENERALLY get better MPG's. (assuming it has enough power to run cleanly on plane) Hull and aero drag increase exponentially to speed, so although the boat weight is similar, the effective load on the faster boat is much more. Goes back to the same thing about a 200 hp will not be 2x as fast as a 100hp, but its going to burn almost double the fuel at WOT. (and i said 'similar' boat weight, you obviously gain a little advantage from a lighter motor also.)

 

[gilcarleton]

Re: Fuel consumption compared to HP and distance traveled

Well I may be out of the loop nowdays. When I was 18 years old I had a friend who had a Plymouth Satellite with a 426 Hemi in it. It came stock with two 4bbl carbs. He said that he was getting about 8 mpg. I had a Satellite with a 383 and I got around 12 -13 mpg. My father had a Dodge Dart with a slant six in it and he got around 16 mpg. Could be the way he drove the car or maybe cars then wasted more fuel than the cars do today. Anyway, this is where I drew my analogy. Getting an accurate answer to my question is somewhat like trying to nail jelly to a tree. There are so many factors in play. Using my line of thinking above, I thought maybe the larger engine would burn more fuel. On the other hand, a smaller engine uses a certain amount of hp to get the boat up on plane. I wondered if the extra hp in the larger engine may be more efficient. I have always used a 20hp on a 14 ft aluminum boat. It went about 30+ mpg and did not burn much fuel. Now that I will be fishing in the Gulf and Mobile bay, I want a larger, center console boat that can out run a storm if necessary yet would not cost me a $100 a day for fuel to fish in. Like I said earlier, I will either run to where I want to fish and cut off the motor and drift or use a kicker engine.