Cigatoo
Guru
My boat has an older 375hp Cat engine. Cruising at seven knots, I average a burn rate of 2 gph.
Nice boat Seighlor. We looked at a couple of Wilbur’s. One was overly modified the other above my pay grade. Beautiful boats!
My boat has an older 375hp Cat engine. Cruising at seven knots, I average a burn rate of 2 gph.
It takes the same amount of energy to push the boat at Hull speed, whether using 300 horse or 75 horse engines. I doubt you could motormuch more economically with smaller engine. 3 gallons an hour is not bad.
Gordon
You might want to read this article which will irritate some about gas versus diesel, you might be better with gas. One stereotype is that gas is the bomb in the back, guys who write this here on these forums after writing it, get in their car with a gas bomb in the back and drive all over. Gas explosions percentage wise on a boat is far less than gas explosions in a car. But in a car we have become used to gas in the back.
What you want to pay attention to is the servicing of diesel engines and the fact that it is expensive and often left undone.
https://www.yachtsurvey.com/GasDiesel.htm
BUT the gas bomb in your car is not enclosed in a space ventilated by an electric fan!!!!! In fact it is very purposefully hung UNDER the car so fumes are dissipated safely!!!!
There is a reason Mainship installed a 300hp+- engine, and not a 77hp Perkins. I recently saw a 395 with a 385hp Yanmar which at displacement/trawler speed was quite economical. Are you sure you know more about engine requirements than the builder/designer?
And balance the cost of the changeover against the possible fuel savings, a kind of cost benefit analysis.You won`t be just swapping engines, there are engine bearers,mounts, exhaust, gearbox mounts, fuel supply, raw water supply, prop shaft modifications, instrumentation and senders, lots of knock on changes to consider.
Maybe run it for a while after you buy one, and see how it looks then.
BUT the gas bomb in your car is not enclosed in a space ventilated by an electric fan!!!!! In fact it is very purposefully hung UNDER the car so fumes are dissipated safely!!!!
From explosion reports I`ve seen,some were associated with refueling,some with work being undertaken,others just while running. I think the replacement of carburetors with EFI helped by eliminating some sources of leakage.If gasoline is so deadly, why aren’t we seeing an uptick in boat explosions with all the new multi outboard CCs? Sure, the powerhead is in the open air, but there are hundreds of gallons of gas under the floor. And they are never grounded when fueling like an airplane.
Well, a NA Perkins 6-354 will push a 35 to 45 foot boat at 7 knots at about 1 gallon per hour.. My Bruce Roberts 44 Ketch used 3/4 gallon an hour on the NA 6-354 You can get a Mainship 34 with that Perkins engine (turbocharged) already installed (factory original) If you keep off the Turbo I would think at 6-7 knots you would get about 1 gph.
Like most everyone that has responded, I too would stick with the larger engine that the boat has in it now. I have a Rosborough 35 trawler, with a Cummins B210 engine. The Rosborough 35 is similar to the Mainship 35, but maybe a little heavier. The Cummins B210 has been a good, economical engine for me. To give you an idea of fuel consumption versus speed for my boat with the Cummins B210:
1000 RPM, 77 HP 1.7 gph 4 Knots
1600 RPM 161 HP 3.5 gph 6.5 Knots
1800 RPM 183 HP 4.6 gph 7.4 Knots
The hull speed for my Rosborough 35 is 7.5 Knots (8.6 mph), so to cruise at hull speed, I actually need 183 HP. I never run over 1,800 RPM, unless I'm trying to blow the soot out of the turbo. The engine makes a lot more noise and burns a lot more fuel at higher RPMs (11.9 gph at 2600 RPM), but because it's a displacement boat, it doesn't go much faster at all. Running at the higher RPM is just a waste of money. We normally cruise with the engine running between 1600 and 1800 RPM. I would not want a 77 HP engine in my boat and be stuck at 4 knots. Running at 7.5 Knots, I can cover 86 statute miles per day and I have enough power to deal with an incoming tide and also to get out of the way when I need to.
New guy here from Ohio.
The Wife and I are Ready to buy a boat. Our intent is to motor around
here and there and all over.
Narrowed it down to a 35 0r 39 Mainship single engine. <snip>
Well being a backyard mechanic I called around the block and a guy with supposedly 38 years experience with cat diesels, in my instance, said that basically you are just removing all of the turbo and afterburner stuff and plugging some holes left by the removal. I am sure you would have to re-tune the injector pump. As for resale you still will have all of the factory parts to put back on. Yes you may want to get a different prop for low end torque.
I am planning on travelling around on this boat not sitting so I can appreciate 1/2 half gallon or more per hour!
In researching online I came to the conclusion that they are taking a standard non turbo engine and pumping it up to way more horsepower causing longevity issues.
I also called Caterpillar Technical Line and they said Oh No we don't recommend changing the factory motors because they are specially built with stronger pistons, connecting rods, cylinder heads to accept the extreme pressures.... Me being an old time Drag Racer I am thinking Oh Boy I would have a much stronger....more well built motor....with suddenly much less strain put to it....In my thinking that makes for a much longer lasting rig.
Correct me if I am wrong.
regards, Gary
I don't know the water conditions in your area, in my area currents can be a significant issue. I want a larger engine so it isn't as stressed at the possible top speed of the boat. But I also want extra Oomph when more power would get me out of a stressful situation.
In the video below, the first half shows a boat successfully and without much stress making it through a rapid current condition in Dodd Narrows in British Columbia. But jump to the 1:05 minute mark, and you might question the sanity of the skipper of that boat. What these mental midgets don't realize is that an engine is designed to handle so much stress, then it over heats, or has the possibility of over heating.
I have a retired Captain from the BC Ferries assist me in decisions with my boat refit and when I was discussing a larger engine (actually the engine is smaller than the old Merc engine but cranks out an additional 110 hp), he said the extra hp would be of benefit in "iffy" currents. He then related a story of one of the larger BC ferries being caught by a swift current and swung 360 degrees before control of the ship could be re-established.
Beginning at the 1:05 mark, you can see the skipper has no margin of error safety in his motor, its going full tilt and we can safely assume being stressed by forces it wasn't designed for: