Adrianp 116 Posted May 25, 2015 Share Posted May 25, 2015 I have a BF20 that's on a trailer sailer that I've been given and am trying to sell (http://www.trademe.co.nz/Browse/Listing.aspx?id=891439399). Seems like a really nice motor for the few times I've used it. 6amp charging as standard and can be upgraded to 12amp I think? If you want to help unbolt it, your welcome to borrow it to see how it fits and goes. I'm really hoping I can sell the boat without the motor as I really want to keep it for cruising on Freedom/hooning around in my RIB. Mine seems to have a smaller prop than the 9.9 yamahas run so that might be a point of difference. I don't know if mine is a high thrust model. I think I remember Phil saying Sundreamer has one of each at the moment and he is trying to go back to the yamahas? Quote Link to post Share on other sites
Tim C 23 Posted May 25, 2015 Share Posted May 25, 2015 I've had two Honda's on Pulse. First one was a 15 hp, the old square model as it was the last one to be upgraded into their current form. It was a very good and reliable engine. A year overseas and not getting used probably killed it, eventually getting gear box problems and a cracked water jacket. Still it did nine years without getting flushed of course. Then there was a 15 hp 'Sail' outboard. It was called a 'Sail' because mostly that is what I did as it was hopeless. Stay well clear. Now I have a 10 hp Honda, only because there wasn't a 15 hp available in the country just before a Coastal when I needed to replace the above quickly. It has an impressive 12 Amp charging and electric start. It's been mostly reliable, a few niggles. It has a vibration at mid revs, but could be in the boat. I miss the extra 5 hp only when going from forward to reverse. I've got the biggest 4 blade prop with fine pitch I could find. On the whole I've been more than happy with the Honda's I've had. Quote Link to post Share on other sites
MartinRF 52 Posted May 25, 2015 Share Posted May 25, 2015 On the whole I've been more than happy with the Honda's I've had. Same here but I have only had one -- an Accord which is 15 years old (Sorry couldn't resist) /Martin Quote Link to post Share on other sites
madyottie 82 Posted May 25, 2015 Share Posted May 25, 2015 Or you could go Nissan... Home > Products > NSF6 Quote Link to post Share on other sites
ScottiE 174 Posted May 25, 2015 Share Posted May 25, 2015 too small if you want to race an 8.5! Quote Link to post Share on other sites
madyottie 82 Posted May 26, 2015 Share Posted May 26, 2015 Only decent picture I could find! Just in response to the Accord comment above it really. I once had an outboard called a Wind 8hp, was made in Russia by a company called Volga motors (seriously). Fantastic motor, ran like a dream once they replaced the faulty ignition coil they'd all been shipped with! If I still had it, I'd be using it!! Apparently the Wind was more reliable than Tim's Sail Quote Link to post Share on other sites
erice 732 Posted September 25, 2016 Share Posted September 25, 2016 an old thread but have been researching prop specs as previously stated the yamaha 8hp 2-stroke is a high power, low weight, popular choice for 8.5mt multis it comes standard with a large pitch 10'? all white prop designed to get light dinghies planning there are also 2 lower "geared" "dual thrust" options for boats heavier than a dinghy that will never reach those speeds the black hubed 9" x 7"N, for light weight multis (9 inch diameter with 7 inch pitch) (cast into the prop alloy) and the black hubed 9" x 5"N for heavier boats with heavy keels the black hub is "dual-thrust" in yamaha speak, which means in-hub exhaust so the blades are less likely to cavitate in reverse and lose bite.............most light tinnys/inflatables etc don't reverse much so don't need this exhaust gas diversion solas also make 5 props for the yami 8hp 2 stroke, the 4 bladed versions with in-hub exhaust probably the best choice for multis http://www.rubexprops.com/boat-propellers/Yamaha/?motor=H0080C&ver=a&model=8HP%202%20Stroke%20(7%20Spline) yachts heavier than 900kg probably want more power AND lower gearing for them the 9.9hp was made with lower reduction gearing to prop (planing speeds not needed) AND a range of dual thrust props for differing boat weights .............. cavitation protection in swells small multis with a single outboard mounted centrally seem better with the long shaft engines as the hulls can lift the prop out in swells + waves yamaha make just the 1 long shaft option but tohatsu make a long and an extra long as Greg has on Mysterex but even the standard long shaft yamaha can still get lifted clear enough for the engine to scream as the prop half spins in air.......one way to help prevent this is to bolt an aftermarket hydrofoil to the engine's small anti-cavitation plate just above the prop http://www.trademe.co.nz/motors/boats-marine/parts-accessories/outboards/auction-1168791372.htm the barnys fitted 1 to capricorn's 8hp 2-stroke yami and it seems to be working well they are just a cut + bent bit of alloy sheet so am going to knock up another out of some spare ally checker-plate for the spare engine also outboard mounts that have multiple down positions help to keep the prop from spinning free capricorn is set so the 2nd from bottom hole for motoring off the mooring, with sails already raised but need the max bottom setting for motoring in, as when head to wind to drop sails, my weight moving from stern to bow, can lift the prop clear from the 2nd from bottom position Quote Link to post Share on other sites
Tim C 23 Posted September 26, 2016 Share Posted September 26, 2016 It's not cavitation. It's ventilation. Air being sucked down to the prop from the surface. Cavitation is very unlikely on the small outboards and speeds we operate at. Quote Link to post Share on other sites
erice 732 Posted September 27, 2016 Share Posted September 27, 2016 yes wonder why they are called cavitation plates? http://www.ebay.com/itm/Sport-Marine-Hardware-f-Volvo-w-Exhaust-thru-Cavitation-Plate-73738-/131585670999 Quote Link to post Share on other sites
Delacruz 1 Posted September 27, 2016 Share Posted September 27, 2016 Yes well we all know that ventilation leads to cavitation ,dont we. Cheers Quote Link to post Share on other sites
Island Time 1,211 Posted September 28, 2016 Share Posted September 28, 2016 As I understand it ventilation and cavitation are different. Ventilation is when air comes down from the surface, causing a "vent". Cavitation is when the low pressure side of a prop or foil drops so low that effectively the water boils, causing an air cavity in the water. Related, but different, and very often confused,even by many who should know better. Quote Link to post Share on other sites
erice 732 Posted September 28, 2016 Share Posted September 28, 2016 maybe it's a bad translation? perhaps the japanese term covers both? certainly yamaha + honda manuals seem to call the plate above the prop that stops air being drawn down the "anti-cavitation" plate in their manuals anyone bored enough to see what mercury + johnson call it? Quote Link to post Share on other sites
madyottie 82 Posted September 28, 2016 Share Posted September 28, 2016 anyone bored enough to see what mercury + johnson call it? I started to search the web, but outboards bore me so instead of just being bored, I quickly became really really bored! Thank heaven for websites like this one! Quote Link to post Share on other sites
paxfish 5 Posted September 29, 2016 Author Share Posted September 29, 2016 Ironically, the cavitation plate could CAUSE cavitation it the tip of the prop is too close! I agree it should be properly known as an anti-ventilation plate. Quote Link to post Share on other sites
samin 0 Posted June 27, 2017 Share Posted June 27, 2017 an old thread but have been researching prop specs as previously stated the yamaha 8hp 2-stroke is a high power, low weight, popular choice for 8.5mt multis it comes standard with a large pitch 10'? all white prop designed to get light dinghies planning there are also 2 lower "geared" "dual thrust" options for boats heavier than a dinghy that will never reach those speeds the black hubed 9" x 7"N, for light weight multis (9 inch diameter with 7 inch pitch) (cast into the prop alloy) and the black hubed 9" x 5"N for heavier boats with heavy keels the black hub is "dual-thrust" in yamaha speak, which means in-hub exhaust so the blades are less likely to cavitate in reverse and lose bite.............most light tinnys/inflatables etc don't reverse much so don't need this exhaust gas diversion solas also make 5 props for the yami 8hp 2 stroke, the 4 bladed versions with in-hub exhaust probably the best choice for multis http://www.rubexprops.com/boat-propellers/Yamaha/?motor=H0080C&ver=a&model=8HP%202%20Stroke%20(7%20Spline) yachts heavier than 900kg probably want more power AND lower gearing for them the 9.9hp was made with lower reduction gearing to prop (planing speeds not needed) AND a range of dual thrust props for differing boat weights .............. cavitation protection in swells small multis with a single outboard mounted centrally seem better with the long shaft engines as the hulls can lift the prop out in swells + waves yamaha make just the 1 long shaft option but tohatsu make a long and an extra long as Greg has on Mysterex but even the standard long shaft yamaha can still get lifted clear enough for the engine to scream as the prop half spins in air.......one way to help prevent this is to bolt an aftermarket hydrofoil to the engine's small anti-cavitation plate just above the prop http://www.trademe.co.nz/motors/boats-marine/parts-accessories/outboards/auction-1168791372.htm the barnys fitted 1 to capricorn's 8hp 2-stroke yami and it seems to be working well they are just a cut + bent bit of alloy sheet so am going to knock up another out of some spare ally checker-plate for the spare engine also outboard mounts that have multiple down positions help to keep the prop from spinning free capricorn is set so the 2nd from bottom hole for motoring off the mooring, with sails already raised but need the max bottom setting for motoring in, as when head to wind to drop sails, my weight moving from stern to bow, can lift the prop clear from the 2nd from bottom position I need a new prop for my boat and this post pretty much summed up the information I needed thanks. Also all the other contributions to this thread, excellent thanks. I will post my results soon Quote Link to post Share on other sites
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