Is it wise to install outboards on pushboat?

[Big Builder]

Hello,

I own a construction company and much of which involves barging. Currently we push our barges with two stroke outboards and it works OK except the burn lots of fuel. I have been weighing the options of buying a tugboat, building a diesel pushboat, or installing outboards on a pushboat or just installing outboards on our barge. We are currently enlarging one of our barges to a dimension of 20' by 55' long. SO I have decided ( I think to build ) a simple pushboat ( 10 wide by 22' long) and install two outboards. This is where I get lost. Shoudl I go two stroke or four stroke?
This vessel is built for pushing only so four stroke probally. But what size? two 90's or 115's or 150's I just don't know how to work that out. I read another post about high thrust outboards..... are these any different?
I guess my last question is the brands? THe closest dealer is evinrude/honda but yamaha is around too. I am not sure about Suzuki but I have two of their motors now and they seem very nice.
I know there is not really perfect answer here but I will really appreciate any help.

Thank you

[powerabout]

Think of it this way
you are trying to make a recreational product do the job of a commercial one.
If you use it once a week maybe the outboard could work out cheaper but if you use it every day how long do you expect it to last?
Re the horsepower choice, go with the lowest horepower of the largest class engine, the smallest V6 will have a larger gearbox and allow a bigger diameter prop than the v4.

Outboards are designed for planning hulls nothing else but that doesnt stop you using them to do anything

[Big Builder]

Yes, I hear that. I have been looking at an odler tugboat that needs a diesel engine installed. I just don't know how hard that is to do either. I appreciate the thoughts.

[gunship]

You cannot afford to have someone install the diesel for you? considering you run a company, and plan on building an entire boat?

[larry larisky]

i think big builder as a very good point. a lot of outboard do professional job, all around the word. they are not toys, quite the contrary.
i will check outboard with 1 : 2.9 reduction, kort nozzle. they exist, they work, and the beauty is, you can bring them in no time to the shop for overall.
i will go for it in a heart beat, having see them working in very difficult conditions.

[Big Builder]

Dear Gunship. I have run a profitable construction business for 22years. During that time I have built all our barges. We push all these with outboards and have had great success with them and considering what we use them for , few problems. THis scow however is larger then the rest. Before Iundertake any project I do my due diligence. Where we operate we are under six months of snow and ice so we have nothing but time. There exists no one in the immediate area who can specializes in marine diesels so trucking a newly built pushboat 500 hundred kms in the snow and salt to have one installed is troublesome Your personal judgements aside ( as well as our financial position) we enjoy these these type of endevours. IT also keeps our employees working
year round.
I have never found pushing with outboards a problem but reversing to land onshore is more difficult.

[Brian@BNE]

Builder
You probably need to give a bit more background to get really good advice. Eg do you operate in river, lake or bay? Are their any draft constraints - if not go for a set-up that has a large diameter prop, low revving. The high thrust outboards aim at this, but won't get the efficiency that comes from the high torque a diesel will give you.

There will be folks here who can give you diesel sizing for your scaled up barge once you outline existing parameters. eg existing barge travels at x knots pushed by 2x y HP outboards. Barge is 1 (or twin) hull, flat bottom, draft of... What kind of loads do you carry - weight in particular.

Another factor is hours/week. IF your hours are low, then the high fuel burn of outboards probably doesn't matter that much. The availability of service nearby and ease of maintenance are pluses. And annual operating cost won't be large compared to initial capital/setup cost.

But if you do run for a lot of hours, then using a diesel that is a truck/car derivative that has been marinised, with your selection based on what brands are common locally should still be OK service/maintenance wise. If you can tolerate the draft then go for a shaft drive, but stern drive or azipod drives might be available in the size range you are talking about. You wont get as big a prop on them, and maintenance will be more.

There will no doubt be regs governing what you can do without running into insurance or licencing issues. I'd think that a push boat will be a long way in front of the bureaucratic entanglement that is likely if you were to power the barge directly.

Sounds like you have a great location and lifestyle - good luck with it all and please post more info on how it all turns out.

Brian

[gunship]

Originally Posted by Big Builder

Dear Gunship. I have run a profitable construction business for 22years. During that time I have built all our barges. We push all these with outboards and have had great success with them and considering what we use them for , few problems. THis scow however is larger then the rest. Before Iundertake any project I do my due diligence. Where we operate we are under six months of snow and ice so we have nothing but time. There exists no one in the immediate area who can specializes in marine diesels so trucking a newly built pushboat 500 hundred kms in the snow and salt to have one installed is troublesome Your personal judgements aside ( as well as our financial position) we enjoy these these type of endevours. IT also keeps our employees working
year round.
I have never found pushing with outboards a problem but reversing to land onshore is more difficult.

Not my personal judgement, rather a question for my personal curiosity.

[MooringProJeffL]

bigbuilder,
Please look over the work barge on this link.
http://www.newenglandmooring.com/con...g-work-barge-m

Twin 4-stroke outboards at 50hp each because of budget restrictions. Each outboard is controlled independantly includng steering. I was able to turn this 200-ft x 15-ft pair of docks with the motors. Low pitch props give it lts of thrust and a top speed of 12mph. The 4-stroke Yamahas are extremely quiet. A normal conversation could be carried on while pushing the docks. Yamaha and Merc make high thrust lower units with bigger gears. I don't have those. The barge is on a mooring now until mid December. It was 26 degrees on Sunday and the motors started with no problems.
I tried uploading pictures to this post but got stumpeed by the technology of the website. I can email better pictures.
My barge is 8-ft-6-inch wide x 24-ft. It may be 10-ft wide next season.

[peter radclyffe]

how about a harbormaster unit

http://www.harbormastermarine.com/

[Big Builder]

Hello everyone,

The tugboat we looked at was not that great so we passed.

Thank you for all the comments. I finally decided to go with a diesel engine. We purchased a 6v53 detroit with very low hours locally. This is not a marine engine though and we will have to marinize it but leave hot exhaust.

We have started building the flat bottom pushboat already (snowy days) and I will need to start looking into transmissions, props and shafts. I will post some questions for that too. I know almost nil about how to calculate the proper transmission, shaft and prop size.

[Fanie]

You will probably do best with a diesel inboard because it has a lot of torque and you can swing a big(er) prop.

Second best is two strokes. Two strokes outperform 4 strokes of the same hp simply because the two strokes have more torque. Two strokes fire every time the piston is up while a 4 stroke fires every second time the piston is up.

The new generation 2 strokes is also within the emission limits, so no problems there, and they can be as quiet as the 4 strokes.

There's a video on youtube where the new e-tech sinks the yamaha. I'll add it here if I can find the link, but imo it's a significant difference. So 90 hp is not 90 hp !!

[Fanie]

Finally -
http://www.youtube.com/watch?v=_-7I00cZUE0

[hoytedow]

E-TEC all the way!

[MooringProJeffL]

That video was pretty good and the claims for equal set up of the motors..taken with a grain of salt. The motor that got the hole shot was going to be the winner because the other motor would cavitate for lack of clean water to pass over the prop. Neither motor brand web site listed their motor's torque. The motors for the push boat may never see 20mph but will be working very hard. The extra lubrication available from 4-stroke motors is why they are used for hard working conditions. Diesel has the most torque and can provide the highest bollard pull. My work boat with two 4-stroke 50hp will do what I need it to do and I don't have to smell 2-stroke oil. Good 2-stroke oil used to run the E-Tec and other high performance jet skis is near the $50/gal mark and not available every where.
Big builder, If you are running hot diesel exhaust, run it 4-ft to 6-ft above the pilot house just like the fishing trawlers do. You can probably find ideas and parts at www.boats-and-harbors.com.