Single or Twin outboards ?????

[Endless Summer]

I have a 16.5 ft petecraft cabin.  I will mount ouboard engines on a bracket instead of an inboard engine.  I am undecided between a big outboard plus a spare engine or twin outboard installation.

Both options give the approx. same total weight.  Prices vary.... but what about performance?

One big + one small....  a 100 hp yamaha plus 9.9 = euro 10000
                               
2 yamaha / suzuki/evinrude etc of 60 hp   = 12,000

2 tohatsu 50                                         =  euro 8000

2 x 50 hp consume the same of a 100hp motor..... Top speed will probably be less with 2 engines...but what if you increase the pitch?  I am assuming at midrange /cruising speed 2 engines are more efficient because the have more thrust. But maybe I am wrong.

Has anyone fitted twin 40 - 70 hp motors on a similar sized boat? 

[placebo]

definitely 2X motors ...... am not sure of the size but for marine offshore safety:

1 engine = 0
2 engines = 1

you'll appreciate more in case one of the engines is in trouble. I think you will do great with 2X 50HP ...... you go to the spot in full speed and then an engine off for trolling.

If you intend do more fishing you'll better think about fuel consumption .... more than 25knts is more than enough for fishing .... after all you will be fishing not racing

[yogi]

i will go for a single installation a 100 or 115 yamaha or selva i do not see any advantage of having 2 motors  it is just extra exp ... other thing if one motor fails the remaining one  will never plane the boat.one other thing a bigger engine have a different power curve

reg

yogi

[Endless Summer]

Unfortunetly outboard motor companies do not give the same detailed info. like inboard engines.  I got fuel consumption figures from performance test on the same websites etc.  Tohatsu give only the WOT fuel consumption but claim to be more economical like all the others !!

Yogi do you thing that one 50 / 60 will not plane a 16.5 petecraft?  I mean plane not a rocket but an acceptable....16 knots cruising ...top 20-22 knots with a light load of 2 -3 persons.  I would be too happy if with both engines it acheives 28 knots (and keeps them when loaded ).   I can try what 1 engine will do as I have a 55 hp 2 stroke yamaha.

An other option would be to couple a 60hp  4 storke yamaha with my current 55 hp 2 stroke....the 4 stroke is ideal for trolling....the 2 stroke will help for speed when loaded.... Or I am mixing sheep with cattle.  The 55h[ 2 stroke is also quite economical to use.

I saw on youtube a 55 and a 75 hp yamaha do a great fast job.  http://www.youtube.com/watch?v=hHSCmP1NM8Y

I already fiddled with a 12 foot boat ...having a 9.9 + 5 hp outboard.   Surprisingly the 5 hp really helped!
My current 17 ft with 55 hp yamaha planed much easier with light and heavier loads when helped by the 9.9 hp....

So I think twins whether identical or not work well!   

[yogi]

i sagest you to speak to the boat manufacturer about minimum hp and maximum hp   if one of the twin motors is close to minimum boat hp it will plane (wot and slow)

mixing 2 and 4 stroke motors is not a good idea ,,

[malvizzu]

As yogi suggested, speak to Mario of Petecraft who will surely give you a sound advise. I have a Petecraft 14 Open with an Evinrude ETEC 50HP. It is the maximum engine I could put on that size. Yours is the Petecraft 17 Sports (with cabin) which a single 50HP would be too small for her. At least you would need a 75HP if not 90HP. The boat is already quite heavy and installing twins would probably mean you have to install trim tabs to help overcome the weight on the transom to be able to plane quickly.

I would definitely go for an Evinrude ETEC. From the past 2 summers I found this engine to be very, very economical. Last week Darius of RLR came up to my garage to make a diagnostic test. I already did 150 hours and during this time I had not even used a whole 4.5L of oil. As regards to fuel consumption, I would not even use 10L of petrol in 6 hours trolling. As regards to performance, it's worth all the money.

The ETECs have the advantages of a 2-stroke engine as regards torque and out-of-the-hole acceleration and as efficient if not more than 4-strokes. The new ETECs have another bigger advantage than mine. Mine has 3 Years / 300 Hours service free but the new ones have a 5 Year warranty. ETECs have around 200 fewer parts to wear out than a regular four stroke engine. This means you spend less time in the workshop and more time on the water.

You might want to send a PM to Fortuna or Destination Sea. They both have ETECs, a 75HP and 90HP respectively if I'm not mistaken.

[Endless Summer]

Thank you all for your views! Napprezza hafna!

[malvizzu]

@ Endless Summer - by the way, with 3 people on board I managed 28.1 knots in a slightly choppy waters.