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Old 28 July 2010, 11:58   #1
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Brand New Bombard 5m Rib, but what Engine?

Just bought myself a 5m Bombard RIB but cant decide what engine to go for. I can get a 50hp, a 60hp which is a grand more than the 50, or a 70hp which is 700 more than the 60. Ive been told that they will all do the same speed, the only thing that changes with the hp is the time to reach the top speed.

I only really want the boat for having a bit of fun around Chichester.

Anyone got any ideas?
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Old 28 July 2010, 14:37   #2
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Just bought myself a 5m Bombard RIB but cant decide what engine to go for. I can get a 50hp, a 60hp which is a grand more than the 50, or a 70hp which is 700 more than the 60. Ive been told that they will all do the same speed, the only thing that changes with the hp is the time to reach the top speed.

I only really want the boat for having a bit of fun around Chichester.

Anyone got any ideas?
As you increase horsepower, you'll undoubtedly increase transom weight, which to some degree offsets any immediate power gains. Where the difference in engines (coupled with a well-matched propeller) will become apparent, is in hole-shot and overall torque.

You need to ask yourself - what's the boat going to be used primarily for, how many onboard, is fuel consumption a consideration or all out top speed? 2-stroke v's 4-stroke, etc. 2-strokes are no longer available to purchase new (except for racing and commercial use), with the exception of Evinrude E-TECs, Tohatsu TLDi, and Mercury/Mariner Optimax which use 2-stroke technology with 4-stroke fuel efficiency and emission regulations.

A good rule of thumb is to whack on the maximum hp that the transom is rated for. However - there's quite a considerable jump from a 60-70hp in terms of weight. Suzuki DF60 and Yamaha F60 weigh in at 110kg and would be good all-rounders. An Evinrude E-TEC 60hp (113kgs), Honda 60hp (119kg), and Mercury/Mariner 60hp (120kgs).

70hp - there's the brand new Yamaha F70A (sweet at just 119kg), Tohatsu 70hp TLDi (143kg), Evinrude E-TEC 75hp (145kg), Suzuki DF70 (155kg), Honda 75hp (163kg) or Mercury/Mariner Optimax 75hp (170kgs). Decisions, decisions!

Yammie get's my vote - no idea regards price though.

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Old 31 July 2010, 09:30   #3
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70hp - there's the brand new Yamaha F70A (sweet at just 119kg), .....

Yammie get's my vote - no idea regards price though
Good looking motor - 2010 price 8499
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Old 31 July 2010, 09:43   #4
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How much???

Nice professional video, aircraft flying overhead then the guys mobile goes off
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Old 31 July 2010, 10:37   #5
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Good looking motor - 2010 price 8499
How much? I've just sprayed my cup of tea over the wall!
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Old 31 July 2010, 10:40   #6
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Crazy money, when you can buy a new Mariner F80 for less than 6k
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Old 31 July 2010, 10:53   #7
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Optimax 75hp (170kgs).
Blimey that's a bit lardy, my old carb 2/ 115hp was only about 140kg!
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Old 31 July 2010, 12:50   #8
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Nice professional video, aircraft flying overhead then the guys mobile goes off
Professional crap video, about 8 seconds of the actual motor!
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Old 01 August 2010, 13:32   #9
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5m Bombard and power requirements

Quote:
Originally Posted by ajwilkins View Post
Just bought myself a 5m Bombard RIB but cant decide what engine to go for. I can get a 50hp, a 60hp which is a grand more than the 50, or a 70hp which is 700 more than the 60. Ive been told that they will all do the same speed, the only thing that changes with the hp is the time to reach the top speed.

I only really want the boat for having a bit of fun around Chichester.

Anyone got any ideas?

Hi AJ, I feel qualified to answer this one as an owner of a 4.85m Bombard Explorer. I have 50hp 4 stroke Yammy on the back of mine. While the 50 is fine for one or two people, once you load up the fuel, safety gear, wife, dog and the beer cooler she gets a little sluggish. I run with two 20 ltr tanks up front and another 20 liter gerry can (1/3, 1/3, 1/3) in the transom well for backup. There are times when things are flat and you want to get up and go, it’s just not there. I get about 42km’s/hr @ 4900 rpm (max rpm is 5500) with current prop and futzing with the trim. I have been told I can do better by re-propping. (it’s on the list).

As it is, it has lots of grab out of the hole and slack on the top end. Throw a guest in up front and she gets even dogyier. I think given the right prop match, you could get that thing to do quite nicely. We were out yesterday in a 1-2’ chop and were able to skitter across the tops of things at 20 to 30 km’s/hr without the wife saying too much..

Bombard recommends 60 and 70 as max. If you and put the $$ together, go for the 70. You are starting fresh, go with max that you can. I would if starting over.

Rick
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Old 02 August 2010, 06:17   #10
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First, Welcom to Ribnet!

It sounds like you have already identified 3 engines.

One thing to remember uis that most outboard manufacturers will use the same basic lump to buiold two or three HP variants. In thatr equation are the "subassemblies" - e.g the lag / gearbox. One prome example was my old Yam 55. I could have taken a leg or gearbox off a 90 to replace it! That to me says the bottom half of my 55 was well over engineered for it's job.

Net result of that is it depends whose engines you are looking at. If you were comparing a 50 to a 60, make "A" may result in a huge weight increase because make "A"'s 60 is a de- rated 70 or 80. make B may result in a negligible increase because the 50 is lardy as it is a de- rated 60.

Always worth having a look a couple of engine sizes either side of the one you want if optimising stuff is the name of the game.
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