splat 55 Posted March 18, 2018 Share Posted March 18, 2018 Hey Team, What is the best outboard for power, weight and fuel economy for a 930? Motor is currently tohatsu 9.8 two stroke. Outboard is mounted vertical in special well on a carriage lifted by rope purchase. Knot me ...what say you? Anyone using a yammie 9.9 hi thrust? Or a 15F stroke? Quote Link to post Share on other sites
ex TL systems 63 Posted March 18, 2018 Share Posted March 18, 2018 The Yamaha 9.9 hi thrust 4 is generally considered the best for bigger boats , I have a fairly late model one on 5 tonne cat and it is great , maybe 6 knots with great bite on the water with the big prop even in reverse, think it is the only one with the bigger prop and 3 to 1 gearbox. Had lots of older ones over the years too and they have been good , around 2 litres an hour and smooth and quiet . I have an older one for sale on trademe now but needs some work and definitely not like a new one which are over 5 k but probably worth it in the long run, cheap compared with a diesel. Quote Link to post Share on other sites
ballystick 72 Posted March 18, 2018 Share Posted March 18, 2018 There are not many outboards that would fit in that well of your board due to size limitations, I'm pretty sure the Yamaha 9.9 is too bulky. It was made for an Evinrude which was lightest at the time and quite compact. 2 strokes use heaps of fuel when cruising and their fumes cause engines to run roughly or even stop so if you can get a more compact 4 stroke to fit in it would be best, also ensure that there is adequate ventilation, a bilge blowing fan made a big difference to engine reliability in the well of the 930 Quote Link to post Share on other sites
S.M.U. 15 Posted March 18, 2018 Share Posted March 18, 2018 I have a Yamaha 4 stroke 8Hp in my R930 and it is pretty much 5 knots into anything and up to 7.5 knots. Bit heavy but very fuel efficient. Quote Link to post Share on other sites
splat 55 Posted March 19, 2018 Author Share Posted March 19, 2018 Thanks everyone....Ballystick is in the know...well is tight now especially with remotes coming in to engine on port side of motor. Getting pretty tired of burning (and carrying) so much gas. Good to see general consensus on 9.9F-stroke if or 8 if possible. Thanks for the input. Quote Link to post Share on other sites
splat 55 Posted March 19, 2018 Author Share Posted March 19, 2018 Knot me-how did you tweak rectifier regulator supply? I ask cause having put a meter on mine the voltage can be quite high and with an AGM batt I really think it needs to be better regulated so as not to damage batt on long runs. Thoughts? Quote Link to post Share on other sites
Island Time 1,235 Posted March 19, 2018 Share Posted March 19, 2018 Rectified supply is what most small outboards have. A rectifier simply converts an AC current to DC. It is unregulated - voltage is not controlled - and can go over 19v at revs on many outboards. It is pretty easy to add a regulator - which does what it says, and regulates the voltage. Can be a simple fixed voltage regulator, or a "smart" 3 stage. Most small outboards can only produce a few amps - they have magnetos not alternators. Many manufacturers can provide a regulator as a standard optional part, often a replacement for the rectifier, with a regulated rectifier... Quote Link to post Share on other sites
Island Time 1,235 Posted March 19, 2018 Share Posted March 19, 2018 Oh, and many small outboard users just connect the rectified supply direct to batts. The voltage is high when the revs are up, but as the amps are low, it normally does not cause the battery an issue, as it does not do it for hours or days at a time. Its not ideal, but they usually get away with it. Quote Link to post Share on other sites
philstar 61 Posted March 19, 2018 Share Posted March 19, 2018 I reckon it really depends if you're racing or cruising. for racing the yamaha 8hp 2 stroke or tohatsu 9.8 2 stroke are both good light grunty engines. We are running a tohatsu 9.8 on our gbe catamaran and its got more grunt and is lighter than the yamaha 8hp. If you're cruising then a heavier 9.9 4 stroke will give you lots of power at the cost of weight. 1 Quote Link to post Share on other sites
splat 55 Posted March 20, 2018 Author Share Posted March 20, 2018 Thanks everyone. IT and Knot me, my concern lies with long runs where the batt is in good condition...almost fully charged and I don't want to have to physically stop and disconnect to prevent overvoltage. I would like to leave connected no matter what...but system voltage shoul never exceed 14.4v (AGM max).Why can't you use a mosfet type controller to regulate? Quote Link to post Share on other sites
ex TL systems 63 Posted March 20, 2018 Share Posted March 20, 2018 They don’t need much of a battery to start you could have a smaller lead start battery which could be switched connected with your agms only when you want to charge them from the motor. I will hook mine this way as I am going to get a new agm house battery but will have a standard crank and winch battery also with the outboard connected to it. Quote Link to post Share on other sites
Island Time 1,235 Posted March 20, 2018 Share Posted March 20, 2018 Mosfet regulators are not uncommon. You can by a suitable regulator off the shelf, why reinvent the wheel? Quote Link to post Share on other sites
splat 55 Posted March 20, 2018 Author Share Posted March 20, 2018 Mosfet regulators are not uncommon. You can by a suitable regulator off the shelf, why reinvent the wheel? Thanks IT Quote Link to post Share on other sites
Priscilla II 392 Posted March 21, 2018 Share Posted March 21, 2018 Problem sorted. https://www.trademe.co.nz/Browse/Listing.aspx?id=1572100358 Quote Link to post Share on other sites
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