Want to act like a trawler

GoSlowGuy

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Jan 20, 2017
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I have a 1996 Bayliner 2655 with a 5.7 and alpha gen. 2. My purpose for this boat is to cruise major rivers. I normally run around 60 to 100 miles each trip and hope to go much further. I move at what would be hull speed on a trawler 8 to 10 knots. This seems to be my pace and saves fuel. The fuel usage is my limiting factor. I am running about 1500 rpm and doing about 3 mpg. Would a change to a merc. 3.0 and proper gearing gain me much fuel range. I know I have the wrong boat for the job but sometimes you gota run what you brung !
 

bman440440

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my 1st thought would be up your pitch to bring down the rpm... does your boat seem to be working hard at the 8-10 knots? if not do that and if it seems like its lugging at those speeds drop it down... you may be turning more RPM's but you might be burning less fuel due to less load on the engine... IMO and I could be wrong
 

alldodge

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I have a 1996 Bayliner 2655 with a 5.7 and alpha gen. 2. My purpose for this boat is to cruise major rivers. I normally run around 60 to 100 miles each trip and hope to go much further. I move at what would be hull speed on a trawler 8 to 10 knots. This seems to be my pace and saves fuel. The fuel usage is my limiting factor. I am running about 1500 rpm and doing about 3 mpg. Would a change to a merc. 3.0 and proper gearing gain me much fuel range. I know I have the wrong boat for the job but sometimes you gota run what you brung !

Howdy

Haven't heard anyone ever wanting to go slower, but hey first time for everything. Your gong to need a certain amount of power just to move the 26 footer, and I'm thinking the 3.0 would be working real hard even at trawler speeds. Going with the current will use less fuel then going up the same land speed. Then if things got bad and you had to move quickly in an emergency.

Do agree that if you have less cubic inches you will burn less fuel with a light load, but feel a 4.3 would be a better choice. You won't have the power to get the boat on plane but will have more power available if needed. Also to changing to the V6 would make an easier engine swap, but would also need to move front motor mounts
 

SeaDooSam

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I agree with AllDodge. A 3.0 would work very very hard to push a 26 ft boat. At most I would drop to a 4.3. It is always nice to have piece of mind that you have at least a little power to get out of emergency situations whatever those may be. You never know when you will have to outrun a storm :D Keep in mind doing this will drastically diminish resale value. Why don't you just sell the boat as is and buy something smaller with a 3.0?
 

GoSlowGuy

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Thank you gentleman,
All good thoughts from people that know boating and know mercruiser. The 4.3 does have merit , it is lighter, it is smaller ( I could use more room in front of the motor) a swap should be less problems, It is an automotive motor so parts should me simpler to find in small town america beside the river. Done deal, 3.0 is too big a change and may cost me in the long term.
I seem to be stuck at 26 foot it is a " bigger boat" sweet spot. It is 8.5 ft. at the beam and can be trailered anywhere without a permit I have a truck to tow it and a nice twin axle trailer. At the marina a 26 foot slip is much less expensive. And I am spoiled by a nice midberth to sleep in, heat and air to keep me comfortable. and a head for any woman on board. But at 5500+ pounds it does take some power to move it in the water . If a boater looks for a long distance 26 foot boat there are few to chose from and the old Bayslimer seems to best first cost boat around.
I am off to work on a boat project ! THANX GoSlowGuy
 

thumpar

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I would keep the engine you have for a couple reasons. You may find you want that power sometimes. I don't think the fuel usage will really be that much if at all. A smaller engine will work harder to do the same thing. The cost savings, if measurable, would not justify the lose of power and cost of a swap. You may later decide to upgrade or change boats and to sell the one you have with a 4.3l in it would be a hard sell.
 

stonyloam

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If you are moving at displacement hull speed it is going to take about the same amount of energy (from gasoline) to move the boat at a given speed. So your V8 with its higher gear ratio outdrive will be turning a lot less RPM than the 6 or 4. So you MAY actually use more fuel with the smaller engine. If you are just cruising it might be worthwhile to look at a larger diameter or higher pitch prop to maximize efficiency. You will be underpowered with the V6 and WAY underpowered with the 4. Remember a boat is not a car, you have to shove a lot of water out of the way to move it, and should you get into a strong current, or tide you will need that V8 power as a safety factor. Just my two cents.
 

ondarvr

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I'd skip the outlay of cash for a new motor unless you needed to repower anyhow, much easier to add a small fuel tank, or carry a little extra fuel only when needed, sort of a no cost immediate solution to a small occasional inconvenience.
 

airshot

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You might try a 4 blade prop to get more propulsion at lower rpm. A lot cheaper than replacing a motor
 

four winns 214

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I've done my share of long distance river cruising, several 200-600 mile trips, in 21' Sea Ray cuddy. I'll bet you won't save one drop of fuel swapping engines and most certainly you'll destroy the resale value of the boat. If you MUST increase range, carry extra fuel. I've done so.
 

Scott Danforth

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Motor size does not impact fuel consumption at slow speed. 0.4 pounds of gasoline per hp per hour. (Standard brake specific fuel consumption for a typical spark ignited marine motor). So if your boat needs 50hp to move, a 3.0 will use the same amount of fuel as a 8.2 liter while generating 50hp

1500 rpm is way too high for trawler speed. The boat isn't moving any faster than it does at 1000 rpm, you're just burning more fuel as the boat is starting to climb out of the hole. At displacement speed, the power required to move the boat is dependent on the hull length. Puttng a smaller motor won't save you fuel, it will just hamstring the boat for when you need to get on plane.

Your boat will get the best fuel economy at about 20mph (just a few mph above planing speed) a fuel flow meter would be required to dial it in. The next best fuel point is at idle while in gear
 

alldodge

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boat will get the best fuel economy at about 20mph (just a few mph above planing speed)

You sure about this one. Look at most any boat test results and they all show max distance below planning speed.

Like Ondarvr post, you could add a bladder tank at least cost
 

Scott Danforth

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you are correct, the highest fuel economy point is below planing speed, just off idle (most peak at 5mpg), the next best is on plane just above planing speed (just about 3mpg). however if you have to go 100 miles, do you want to take 33 hours (or more with a head wind) to get there or 5 hours to get there. the difference is not significant enough to meander along for the extra 28 hours. (20 gallons of fuel vs 33 gallons, or about $30)

if you want fuel economy in a boat, get one with sails or oars

regarding the OP's desire to run more than 100 miles. I have a 75 gallon tank on my boat, a normal outing for us is about 80-120 miles just to hit all the spots we want to go. I use about 30 gallons per trip, spend the day with friends and family swimming, tubing, skiing, hitting a few bars/restaurants and visiting many friends

typical-boat-trip.jpg
 

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H20Rat

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I'd second the kicker idea... There are brackets out there that allow you to mount a decent size kicker, and you can plumb it into your normal fuel tank.

As alldodge mentioned, it still takes a certain amount of power to move at a specific speed, but there are ways to cheat that. A big carbed engine idling to generate 10 hp of thrust is using quite a bit more fuel than a smaller EFI (or even carbed) engine running at peak torque to generate that same 10hp of thrust. You have to consider how much fuel isn't being burnt, along with how much is being used to generate power. Idling engines are not efficient engines.
 

redneck joe

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re: kicker - I'm still having (we believe) carb issues when hot and can't keep/get mercruiser to start until cooled off. and I've used my kicker (15hp 4 stroke on a light and skinny 23') and never looked at fuel consumption but locked in straight, and 30% throttle i'm 3-6 mph depending on upstream, down, or on lake. Steering from helm is functional.

power is only missed when the time arises and you need it.
 

GoSlowGuy

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Jan 20, 2017
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Oh boy,
This is a lot of input and a lot of ideas. and I am glad to have so many minds working on the same problem. Maybe I should say that I know boats use fuel and much more than land craft. I don't want to reinvent the wheel ( or in this case the dug out canoe ) just want to travel as far as possible. I guess the root of the problem is I know that displacement hull boats that are designed for this kind of service do much better and have a longer range. But is that due only to the hull design or is it at least partially due to the engine design and usage. I was told horsepower sells boats and torque moves boats. So an engine with torque output that matches the load should perform best at a fixed speed. The 5.7 is good for 350 ft. lb. torque and can push my boat at about 30 mph on plane. I don't have to explain the fuel usage at WOT. An 80 hp perkins diesel with 220 ft lb. can push a 48 foot sail boat all day long on what I burn in an hour. Is it the planing hull or is it the power source. I once read that a planing hull can never carry enough fuel to get out of sight. I hope the author was wrong.
After reading all of the great posts the chevy small block has at least one more season in my boat. I will spend more time on plane and the idea of a fuel flow meter is a good one. The prop is ? I took it off my other boat and don,t know the pitch. Will check that out. I am running a holley 4 brl that I made into a 2 brl and solved some idle problems, still gets me on plane just slower. Once I start her back up I will try to dial it in. The kicker idea may be the answer and that will be another choice to make later. Thank all of you and you are a great resource, you will make my boating a lot more fun .
>>>>>>>GoSlowGuy<<<<<
 

bobkat1864

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Here on Lake Erie, you see a lot of boats with small kicker motors, in the 10-15 hp range. People troll with em all day long to save fuel, oh and having that little motor to use in an an emergency can sure come in handy. I don't have any exact numbers on fuel consumption, but those little outboards are quiet, and sip gas...if you need more go, just start up the main...best of both worlds I guess. Being out of sight of shore with only one engine for maneuvering would make me feel a bit uneasy. Murphy is always close by.
 

H20Rat

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The 5.7 is good for 350 ft. lb. torque and can push my boat at about 30 mph on plane. I don't have to explain the fuel usage at WOT. An 80 hp perkins diesel with 220 ft lb. can push a 48 foot sail boat all day long on what I burn in an hour. Is it the planing hull or is it the power source.


All the above and then some. Diesel fuel has about 15% higher energy content, and the engine is generally more efficient at burning its fuel. The displacement hull and speed also play a huge factor. Push that sailboat around at the same speed and it would be a different story!
 
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Scott Danforth

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Diesels burn .333 lbs of fuel per hp per hour
Spark ignited motors burn .4 lbs of fuel per hp per hour.

Diesel fuel also has a higher BTU output than gasoline and the better efficiency mentioned.

Diesels will always get better fuel economy than spark ignited

A sail boat hill is designed to be the most efficient it can be at displacement speeds. The longer the wetter hill length, the greater the displacement speed.

Your planing hull is designed to be up on plane. While you desire to put along to get further on a fixed amount of fuel, you also need to be a realist.

The diesel in a sailboat is intended for docking, and for moving the vessel when there is no wind. Sails (wind) are the main source of propulsion. Sailing ts the most fun you can have at 7 knots.

Do you have 33 hours to go your 100 miles while at idle, or do you use the boat to enjoy time on the water bring the boat on plane and cover 100 miles in 5 hours for a few more gallons of fuel.

Kicker motors for fishing are intended to push the boat slow.... For the propper trolling speed which is usually half of what the idle speed is of the main motor. Their main function isn't fuel economy, it's propper speed for fishing.

Trying to jump thru gyrations to force a boat into something that it's not will ruin the enjoyment of boating.

Years ago I stayed "Once you accept that a boat is a hole in the water you pour money into, you can enjoy boating". It is still relevant today.
 
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