Rgvkiwi 15 Posted October 3, 2023 Share Posted October 3, 2023 Looking for advice on replacing our old, working pefectly 9hp Tohatsu 2 stroke. Tohatsu seem well priced and it likely ensures our fuel line and charging lead will fit but open to suggestions on alternative brands if there is any benefit. Mostly, i'd like to know if there is any benefit to going to a 4 stroke engine other than not worrying about premix. Im attracted to 4 stroke for less noise and smell BUT am worried the weight difference on the outboard bracket might be a bit much, though I can likely beef up the boat side mounting. Current engine weighs approx 26 kg and the 4 stroke equivalent is 39kg's. I presume a 4 stroke has better torque which might be an advantage? Quote Link to post Share on other sites
khayyam 69 Posted October 3, 2023 Share Posted October 3, 2023 Why are you replacing it? 26kg vs 39kg is a big difference for lifting on and off the back, imo. Quote Link to post Share on other sites
Rgvkiwi 15 Posted October 3, 2023 Author Share Posted October 3, 2023 5 minutes ago, khayyam said: Why are you replacing it? 26kg vs 39kg is a big difference for lifting on and off the back, imo. Its semi permanently mounted. Removed annually for new waterpump and service. Repalcment is age related. Just for safety and reliability, plus the cover is held on by a ratchet strap as the rubber seal is apparently unavailable, looks tatty. For the safety of the family, and the by the time we sell the old one, the cost isn't massive. I had a scare last season, turned out to be spark plug related and easily fixed but it REALLY put the shits right up me being stranded out in the gulf with wife and 7 year old daughter on board. Quote Link to post Share on other sites
eruptn 95 Posted October 3, 2023 Share Posted October 3, 2023 The key is the prop, make sure you have the sail drive or displacement version. 1 Quote Link to post Share on other sites
GFT 1 Posted October 3, 2023 Share Posted October 3, 2023 If you can, find a Yammie 8hp 2stroke with the high thrust leg, shifts along an SR26 at 7 knots. Best out board I've ever used on a race boat. 90% of the 8.5 multi fleet use them. Mines never been flushed or had a water pump replaced in my ownership. Motored to Auckland and the bay a couple of times in no wind. Bonus is it has a rectifier so I charge the battery and use the auto pilot. Only thing to ever break was the gear shift lever. The key is to run them 50:1 and run them out of fuel after use. 1 Quote Link to post Share on other sites
Ex Machina 366 Posted October 3, 2023 Share Posted October 3, 2023 2 hours ago, GFT said: If you can, find a Yammie 8hp 2stroke with the high thrust leg, shifts along an SR26 at 7 knots. Best out board I've ever used on a race boat. 90% of the 8.5 multi fleet use them. Mines never been flushed or had a water pump replaced in my ownership. Motored to Auckland and the bay a couple of times in no wind. Bonus is it has a rectifier so I charge the battery and use the auto pilot. Only thing to ever break was the gear shift lever. The key is to run them 50:1 and run them out of fuel after use. What about the 4hp outboard on my raceboat ? That got your ass to Auckland for the last coastal ! But yeah I’ve had the same model yammy 8hp with high thrust prop on a previous boat . Did multiple 12-14 hr trips to Auckland and it never missed a beat . Also a bonus is Yamaha parts service , they are very good . 1 Quote Link to post Share on other sites
Flaming lips 1 Posted October 3, 2023 Share Posted October 3, 2023 Just put a 6hp 4 stoke Yamaha on Flaming Lips, only used a few times so far but pushed her along nicely at 6kt in flat water with a very dirty bottom or 4+ into 15 knots of breeze. very clean and quite, comes in at 26kg. Quote Link to post Share on other sites
Rgvkiwi 15 Posted October 3, 2023 Author Share Posted October 3, 2023 10 hours ago, Flaming lips said: Just put a 6hp 4 stoke Yamaha on Flaming Lips, only used a few times so far but pushed her along nicely at 6kt in flat water with a very dirty bottom or 4+ into 15 knots of breeze. very clean and quite, comes in at 26kg. Interesting alternative, quiter, no oil to premix and that is slightly lighter. My only concern would be in swell. Does it reach as deep as the old motor? In larger or shorter harbour type swell or chop we will have the motor out of the water on occasion. Quote Link to post Share on other sites
NZTiger 17 Posted October 4, 2023 Share Posted October 4, 2023 I've just moved to a 4 stroke, 10hp, ultra long shaft outboard for our GBE catamaran. It's outstanding in the chop, doesn't seem to cavitate at all, and is two cylinders so a bit quieter than a 2 stroke. Unfortunately, it weighs about 45kg which is quite a handful getting in and out of the outboard pod. I'm 6 foot 4 and it's probably the limit to what I could manage (needs to be a one person job because two people get in the way of each other if they're both trying to do it at once). I think I can make it easier by adding some shoulder carrying straps to the motor, but it's not for the feint hearted. I think it would be even more difficult getting it on and off an outboard bracket mounted on the stern of the boat - so you might want to consider that aspect. For me, if there was a 2 stroke, ultra long shaft motor, between 8 to 10hp, I would jump at it. I would happily sacrifice the quietness of the 4 stroke for the weight savings of the 2 stroke. (Also, in my experience, two strokes can be neglected a bit more than four strokes). I've happily used a long shaft, 6hp, four stroke in the past which gets the boat along nicely when there's no wind, but we need to consider what happens when we're pushing into rough conditions and there's an issue with the rigging which means sailing is not an option (which happened to us last year) and motoring out of trouble is the only choice left. 1 Quote Link to post Share on other sites
GFT 1 Posted October 4, 2023 Share Posted October 4, 2023 22 hours ago, Ex Machina said: What about the 4hp outboard on my raceboat ? That got your ass to Auckland for the last coastal ! But yeah I’ve had the same model yammy 8hp with high thrust prop on a previous boat . Did multiple 12-14 hr trips to Auckland and it never missed a beat . Also a bonus is Yamaha parts service , they are very good . Yeah its hard to forget motoring upwind, against tide along the eastern beaches for 4+ hours getting fire hosed at 2 knots .... Quote Link to post Share on other sites
Flaming lips 1 Posted October 4, 2023 Share Posted October 4, 2023 10 hours ago, Rgvkiwi said: Interesting alternative, quiter, no oil to premix and that is slightly lighter. My only concern would be in swell. Does it reach as deep as the old motor? In larger or shorter harbour type swell or chop we will have the motor out of the water on occasion. We got the long shaft option, same as the old one and have it mounted on the transom. Dropped all the way on the bracket works fine in all but really short steep sea states then you get the occasional cavitation. 1 Quote Link to post Share on other sites
Interstellar Overdrive 3 Posted October 4, 2023 Share Posted October 4, 2023 Switched from a 8hp 2 stroke Yamaha with high thrust prop to a new tohatsu 6hp 4 stroke sail pro (ultra long shaft) on our Ross 780. Outboard mounted on bracket out back. Love the tohatsu would never go back to 2 stroke. SP model comes standard with yacht specific prop, charging system and ultra long shaft. 2 Quote Link to post Share on other sites
Rgvkiwi 15 Posted October 4, 2023 Author Share Posted October 4, 2023 13 hours ago, Interstellar Overdrive said: Switched from a 8hp 2 stroke Yamaha with high thrust prop to a new tohatsu 6hp 4 stroke sail pro (ultra long shaft) on our Ross 780. Outboard mounted on bracket out back. Love the tohatsu would never go back to 2 stroke. SP model comes standard with yacht specific prop, charging system and ultra long shaft. Thats great to hear....Are you in the Hauraki Gulf, have you had it out in any adverse weather? I'm really keen on the 6hp 4 stroke after yours and Flaming lips experience but the 3 HP difference worries me for wind on the nose, swell/chop conditions....??? per this kind of comment... I've happily used a long shaft, 6hp, four stroke in the past which gets the boat along nicely when there's no wind, but we need to consider what happens when we're pushing into rough conditions and there's an issue with the rigging which means sailing is not an option (which happened to us last year) and motoring out of trouble is the only choice left. Quote Link to post Share on other sites
Rgvkiwi 15 Posted October 5, 2023 Author Share Posted October 5, 2023 Just realised both your boats are slightly shorter, was having a senior moment and forgot ours is an 830. So the power output of the 6hp is probably a real concern in weather. So now im looking at the Tohatsu 9.8 4 stroke. Just heading up tonight to check what bracket we have, if it's a real tenob they are rated to 20 hp long shaft and 50 kg's. Quote Link to post Share on other sites
raz88 96 Posted October 5, 2023 Share Posted October 5, 2023 Years ago I sailed on revolution blues (830). It had a tohatsu 9.8 2 stroke on it which seemed to perform well and I remember a conversation at the time about how it was the lightest of the 9.9ish hp motors. Quote Link to post Share on other sites
Interstellar Overdrive 3 Posted October 5, 2023 Share Posted October 5, 2023 3 hours ago, Rgvkiwi said: Just realised both your boats are slightly shorter, was having a senior moment and forgot ours is an 830. So the power output of the 6hp is probably a real concern in weather. So now im looking at the Tohatsu 9.8 4 stroke. Just heading up tonight to check what bracket we have, if it's a real tenob they are rated to 20 hp long shaft and 50 kg's. Yes the 6hp is adequate but probably right on the bottom end we would want for the R780 which is probably quite a bit lighter than the 830. I think we are bang on the minimum kw/m length allowed in the YNZ Regs for racing (but that might just be the trailer yacht requirement). We’ve had no issues with push in the gulf and coming back up the Weiti against the tide, but never been in really snotty stuff as it’s no fun in a lightweight R780. For the 830 I would tend towards the next size up. The only downside will be lifting it off the transom if you store it in the boat. The 4 stroke is fantastic for economy and noise but the single does vibrate a little more compared to the 2 cylinder stroke. If you can live with the weight a 2cyl 4 stoke would be perfection. 1 Quote Link to post Share on other sites
Rgvkiwi 15 Posted October 5, 2023 Author Share Posted October 5, 2023 5 hours ago, raz88 said: Years ago I sailed on revolution blues (830). It had a tohatsu 9.8 2 stroke on it which seemed to perform well and I remember a conversation at the time about how it was the lightest of the 9.9ish hp motors. Nice, this is revolution blues we're talking about Age of the motor a good part of my reasoning, funny to think its the exact same motor you used and discussed all those years ago! 1 Quote Link to post Share on other sites
raz88 96 Posted October 5, 2023 Share Posted October 5, 2023 Personally I'd be hesitant to nearly double the weight hanging out the back on that bracket. I'm pretty sure I remember it being an 8 that was on there prior, so the 9.8 was already an increase. IIRC this was done about 10-12 years ago, so motor isn't a spring chicken but also isn't as old as many... Few things to consider: A) what can the bracket handle? not just a concern in terms of raw weight sitting on the bracket at rest in the marina, but as the boat bounces up and down in chop, inertia will mean theres more than 40kg of force being put on the bracket and its mounts. b) lifting on and off. Although not a huge deal if not doing it often. C) in general adding weight to the ends of a boat is bad for performance. It increases pitching. Plus when it's out on a bracket/lever an extra chunk out the back, the effect is magnified. 830s are light boats and quite weight sensitive - you'd want to be sure it's not going to make the boat behave badly when you try to sail upwind in a chop. 1 Quote Link to post Share on other sites
raz88 96 Posted October 5, 2023 Share Posted October 5, 2023 On 3/10/2023 at 1:51 PM, Rgvkiwi said: I had a scare last season, turned out to be spark plug related and easily fixed but it REALLY put the shits right up me being stranded out in the gulf with wife and 7 year old daughter on board. Slightly off topic, but do you have a coastguard membership? They'll tow members home for free if you have a mechanical failure. 1 Quote Link to post Share on other sites
Rgvkiwi 15 Posted October 5, 2023 Author Share Posted October 5, 2023 5 hours ago, raz88 said: Slightly off topic, but do you have a coastguard membership? They'll tow members home for free if you have a mechanical failure. I didn't, but do now, thank you for the reminder. That will be huge peace of mind in the event of trouble. 1 Quote Link to post Share on other sites
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