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Old 14-04-2016, 18:15   #1
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Extended transom and outboard engines

I am contemplating purchasing a trawler to cruise the west coast, inside passage to Seward Alaska and then cruise the PWS. The boats I have looked at are really well laid out and look comfortable for the 3 year journey. The issue I have is the engine noise!

I went fishing on a 26' Osprey with a 250 Hp motor on an extended transom. I had to look at the tach to see if the motor was running. It was that quiet.

I was thinking of purchasing a 40ish foot trawler and having the engines removed and sold. Then I would install an extended transom and mount two 150 HP engines. If I space the engines just right I should be able to have a "dingy slip" nosed between the two. I would install hydraulic jack plates so I could tilt the engines fully up to get the foot out of the salt water.

I would gain space, eliminate noise and the engines come with a 6 year full warranty (sort of).

Of course I would have to buy the boat "right" to justify the cost.

Do any of you see any downside to this way of thinking?
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Old 14-04-2016, 18:35   #2
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Re: Extended transom and outboard engines

Those two engines would probably cost... $30k! You likely already know that. Sounds like you want a power cat.
But it does gain you redundancy if the original is single screw. Cabling and controls for those duals will be exposed and a bit complicated, but it's very doable. Keeping them aligned for steering may have it's problems, but solvable.
Not sure how those big outboards do at low rpm fuel wise, they guzzle at higher speeds. I guess the question is how much HP do you need to move at trawler speeds. Not sure if props pitched for slow speed are available. Not sure you want to idle those engines continuously....
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Old 14-04-2016, 19:09   #3
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Re: Extended transom and outboard engines

Good points. I have submitted the idea to Suzuki, Honda and Yamaha. I am awaiting their reply. I have several fishing friends who idle their boats all day long with no issues.

I look forward to hearing from the manufacturers.

Thanks again.
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Old 14-04-2016, 19:18   #4
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Re: Extended transom and outboard engines

I know nothing , but that has never stopped me before ! At trawler speeds with the correct props maybe 40 or 60 horse motors would do just as good . No advantage to the bigger engines !
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Old 14-04-2016, 19:39   #5
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Re: Extended transom and outboard engines

Good point. I have been trying to find someone who can do the calculations or find someone who has successfully made such a modification. Smallest motor that can do the job the better and cheaper.

Thanks
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Old 14-04-2016, 20:11   #6
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Re: Extended transom and outboard engines

You have a couple of issues...

One you will need to buy a boat built with gas engines not diesels. Which is going to be vanishingly rare on a 40' trawler. Otherwise you have to also rip the entire electrical system out of the boat and have it rewired in compliance with gas standards. One of the advantages of diesels is that the fumes can't explode, but if you convert to storing gas onboard you have to deal with the fumes.

Two. Take a look at high thrust outboards. For a 40' probably twin 50T Yamahas, then compare the rpm and prop size to installed diesels. The new four strokes are whisper quiet at idle, but at 3500rpm scream. Even with high thrust outboards you probably won't have big enough props so cavitation will be a concern.

Three. Fuel economy. Diesel fuel is more energy dense, and inboards are more fuel efficient than outboards. Add the too small prop, and you are likely to get pretty bad fuel economy compared to a diesel.

Four. Resale value. It may be worth it to you, but I doubt anyone else would be interested in this setup.

Five... Twin 250's are not going to be $30,000. The quote we just got to repower our fishing boat with twin 140hp is $28,000 plus a new wiring harness.

Six. Presumptively the generator is a diesel? So you will loose the ability to run a generator for power.


It might be interesting to explore this, but I don't think the tradeoffs would work for me.
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Old 14-04-2016, 20:20   #7
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Re: Extended transom and outboard engines

On a planing hull the outboards won't have a tendency to be lifted out of the water, however on a 40ish foot trawler they could be quite easily. And at the time that you'd not want them to be. All in all I think this is an awful idea as an add on. Purpose built maybe, but not a conversion.


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Old 15-04-2016, 06:20   #8
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Re: Extended transom and outboard engines

Keeping the propellers in the water during really bad sea conditions is the only issue I can foresee.
Take a look at the new Evinrudes, they have built in steering, tilt trim. When you run aground you can tilt them up, get in the water and push the boat off the sand bar back into deep water.
Select a fly bridge fiberglass cruiser or trawler with gas engines that will simplify the fuel tank issue.
Examples are: 40 ft 1974 Pacemaker, Hatteras, Chris Craft or Bertram
Don’t plan on getting much pay back from selling the engines, but it may cover the cost of removing them.
I would install additional water and waste tanks, and a larger house bank in place of the engines.
I would also make the fly bridge roof extend all the way to the stern with solar panels.
My idea of cruising is going slowly enjoying the trip, twin 40HP are all that is needed BUT there are times when you will be against strong wind and current as such you will need to add power to make headway therefore twin 150 should be more than sufficient. Also larger engines will have larger propellers and larger alternators.
I live on the Atlantic Intercostal Waterway, yesterday a big north bound sailing catamaran went by with brand new Evinrudes on the ends of the hulls. The idea is catching on
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Old 15-04-2016, 08:51   #9
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Re: Extended transom and outboard engines

Thanks for the input. I was just in St Petersburg and a guy just had outboards installed on an Endeavor trawler Cat. We were talking with the owner of Endeavor and he was about to start building a new Trawler Cat with outboards for another customer. Inside the Cat we could not even hear the engines run.

I also agree the slower the trip the better. I always hate arriving. The trip is what I enjoy the most so speed is not important to me except when outrunning a storm or overpowering wind and current. However I am accustomed to seven to nine knot limit with my sailboat.

I will start looking for gasoline models. Excellent suggestion.
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Old 15-04-2016, 09:40   #10
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Re: Extended transom and outboard engines

And the gasoline powered boat will be way cheaper to purchase. If you're going to dispose of the engines, why pay for a diesel. Good luck with this interesting project. When you're done, post and let us know how it went.
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Old 15-04-2016, 09:51   #11
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Re: Extended transom and outboard engines

"Five... Twin 250's are not going to be $30,000. The quote we just got to repower our fishing boat with twin 140hp is $28,000 plus a new wiring harness. "


OP said 150's.


OP's talking a 40 ft trawler... that's pretty big and a lot of windage. I doubt if it had a diesel it would only have 100HP total..? In flat water fine, but....


"...Otherwise you have to also rip the entire electrical system out of the boat and have it rewired in compliance with gas standards. One of the advantages of diesels is that the fumes can't explode, but if you convert to storing gas onboard you have to deal with the fumes. "
Not much difference at all in the electrical..... especially with the engines out of the boat. I've managed the building of 100's of gas boats to ABYC standards. Really wasn't anything done different than I've seen done on most sailboats etc.
Still, it will be an albatross for sure, having minimal value to anyone but the original owner, unless it's a Cat.
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Old 15-04-2016, 10:55   #12
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Re: Extended transom and outboard engines

This concept of a trawler-type liveaboard with outboards is being built now by Great Harbour. Hubby Dan and I ordered the first one; it is under construction now and due to be delivered in November 2016.

Great Harbour N37 trawler: spacious, stable, unsinkable - Great Harbour Trawlers

Look at the blog and other locations on the website. You will get much more info. We are getting the twin Suzuki 60's.
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Old 15-04-2016, 12:49   #13
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Re: Extended transom and outboard engines

Nice boat. So I assume you got the N35 since the web site shows the N37 only comes with inboard engines.

This is an even better option due to the trailer ability. East Coast to West Coast with no panama canal!
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Old 15-04-2016, 12:59   #14
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Re: Extended transom and outboard engines

Quote:
Originally Posted by Lance835 View Post
Nice boat. So I assume you got the N35 since the web site shows the N37 only comes with inboard engines.

This is an even better option due to the trailer ability. East Coast to West Coast with no panama canal!

Scroll down on the linked page, it discusses the TT35 with outboard propulsion.


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Old 15-04-2016, 23:43   #15
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Re: Extended transom and outboard engines

We purchased the TT35, not the N37. This new line of boats by Great Harbour has many features that appeal to us. Before we purchased, we met with the owner of the company, Ken Fickett, and the Marketing Director, Pierce Hoover.

We visited them down in Ft. Myers and looked over a used N47 trawler and a used N37, both quite impressive. Unbelievable fit and finish doesn't even begin to describe their N-series boats. Ken was into shallow draft and economical cruising long before it became fashionable. The thing that struck us most about his boats was how common-sense they are. All systems, electric, plumbing and mechanical are easily accessed, and it is obvious that tremendous forethought concerning maintenance went into the design.

Ken's innovative trawler hull design (I'm still referring to the N-series), with the thick thick fiberglass below and innovative lightweight and very strong materials above, produces a vessel that is superior in seaworthiness and economy. Seeing first-hand the engine room access, the fuel polishing systems, and the ease of maintenance compared to most other trawlers was an eye-opener for us. These guys build amazing boats.

So when we saw Ken's blog about the TT35, we realized that this is the boat for us. Look a little more closely at the website.

The TT35 is not a displacement hull. It is a planing-style hull with a sharp bow and 6 degrees deadrise at the stern. I understand the desire to put outboards on a displacement hull, however, I wonder if you might be disappointed. If it were me, I would look for a boat similar to the design specs of the TT and go from there, i.e. do what the experts at Great Harbour are doing. And the new Suzuki four-stroke outboards appear to be way ahead of the rest of the pack when it comes to fuel economy.
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