Outboard motors for boats

[spottedtango]

Hello guys,

Was interested about starting a new hobby, getting away from bikes for a bit and I've got the notion to buy an outboard with the idea of fixing it up and attaching it to a small boat.

I understand bike engines but I know fuck all about boat engines. Just interesting to see what makes have what problems, what to get and what to avoid. If anyone can shed any light.

From what I've read I'd be looking for a two stroke around 15/20bhp for a decent turn of speed. Boat would be fairly small 8/12ft approx.

[MCN]

Outboards can be as much PIA as motorbikes. But you canny push a boat to the petrol station.

The most reliable are 4 stroke.

They need more maintenance than bikes.
When they come out the water the cooling system needs to be flushed with fresh water and added inhibitor if you want.

Small 3 cylinder. Would be good.

Most have electronic ignition.
I think fuel injection too.
Fuel needs to be spotless clean and fresh.
Dirty/stale fuel can leave you stranded.

Make sure the engine is matched to the boat.

Hull size and shape.

Bigger engine/s might not mean faster when it comes to boats.

Buy and use life jackets. It's embarrassing to be hauled out the water lifeless.
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Disclaimer: The comments above may be predicted text and not necessarily the opinion of MCN.

[WD Forte]

Spend money on whores first, whores can get you out of trouble
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bikers smell of wee

[MCN]

[stinkwheel]

Same issues as bikes. There is a lot of chinese shite out there.

Buying second hand, I'd go for one being sold by a marina ona freshwater lake off one of their rescue boats. They'll usually have been regularly serviced and haven't been exposed to salt.

My Dad always used to have problems with the water cooling impellars corroding/seizing on outboards. Also nobody ever changes the gearbox oil in them.

There are the usual Japanese makes, same as motorbikes. Tohatsu also seem to do a decent budget motor.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Polarbear]

Horrible things to work on unless you have a workshop and decent stand for them. When I was doing boat repairs I started repairing them alongside diesel engines but soon decided to give them up. Almost impossible to work on site. A sod to lift on and off the boat and spares are expensive.

Buying for a bit of fun to do up for yourself is a bit different of course. No time constraints or budgets to consider.

As for makes. Same as bikes the Japanese are best in my view. I had a Honda as my personal engine on my old cruiser, totally reliable. Yamaha has a good reputaion as well. I wouldn't go 2 stroke but that's a personal choice.

TBH if you are talking a dinghy I would be inclined to either go electric or buy a cheap as chips Seagull for the lols.
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Triumph Trophy Launch Edition

[Islander]

All that's been said already pretty much covers it. I'll add another manufacturer to the mix though, and that's Evinrude. Good solid workhorses.

[stinkwheel]

Aye, an old seagull would be fun to work on, super simple. The outboard equivalent of a CG125.

As above, hard to know why you'd want a 2t unless it's one of the utterly bonkers 250bhp+ fuel injected V5 things the Yanks like to put on small pleasure craft. A wee tohatsu/evinrude/yamaha 4t will purr along all day long and you won't find yourself hanging over the back of the transom in a 10ft swell trying to change a fucking sparkplug.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[stinkwheel]

Oh yeah. The recoiling pull starts fuck up for fun too, usually at the least oppertune moment so if it doesn't have an electric start, make sure that's in good order and put a new rope on it long before it starts looking worn. Unless you get a seagull where you just wrap any old bit fo rope around the pulley, you can start those with a shoelace.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[spottedtango]

No worries, my logic was small boat lighter engine with some power and I'm not sure of the hp rating. As I say I'm just beginning to do a bit of research into it.

I'll maybe switch to the honda 5hp 4 stroke outboards to get used to servicing them and maneuvering them about. Hadnt thought about the weight. I've got a spare wheelie to stick it in to test the water pump and flush it through when I get it.

Will 5hp be enough It'll mostly be used on lochs and lakes. The boat will be getting loaded up with some camping gear and another person at the most

[spottedtango]

Also whats purpose of a short shaft Vs a normal length one?

[Nobby the Bastard]

[stinkwheel]

[spottedtango]

I had a look at that as it's easy to put away and maneuver to the water.



https://www.ebay.co.uk/itm/145152193013?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=duaDrITMSma&sssrc=4429486&ssuid=mHPF4q5oTHC&var=&widget_ver=artemis&media=WHATS_APP

If you read the description the guy says about it being a superior design for the hull. I've no idea what makes a decent hull but I'm assuming a 4t outboard would be able to push that at a satisfactory rate

[stinkwheel]

[Polarbear]

[MCN]

I believe the normal approach to motorboats is to buy the boat you need, then match the Engine to the boat.

Most often they come as a set.

A marine engineer has already worked out the keel to horsepower numbers for the rig.

And remember, a boat is not just for Christmas.
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Disclaimer: The comments above may be predicted text and not necessarily the opinion of MCN.

[virus]

[stinkwheel]

[The Artist]

https://i.redd.it/73cwoawe7lab1.jpg

225hp should be enough

[Serendipity]

I have a small inflatable that I use on the Thames and occasional jaunts on the salty stuff. I’ve popped across to the Isle of Wight a few times and went exploring the west coast of Scotland.

I’ve got a little Honwave T38 which is a fully inflatable model with a high-pressure floor so there’s no fecking about with aluminium panels and stringers. Just drag it out of the car, inflate and go. If you want to carry dogs or do lots of fishing, the boats with ply or aluminium floors might be more suitable.

I have 2 engines for mine. For the river I use a little 6hp Yamaha four stroke. It’s quiet(ish), non-smoky and very frugal on fuel. The Thames speed limit is 5mph and with 2 people and a picnic that engine would struggle to break the limit. Solo it will just about get the boat up and planing to about 13mph, but like a 125 bike you wouldn’t want a headwind or it’ll slow down.

For more spirited hooning out at sea I have a 25hp 2T. It’s badged as Mariner, but actually made by Tohatsu. It’s noisy and gulps fuel but smells great and goes like stink. It’ll get the boat on plane with four adults and I’ve had 30mph out of it solo. Which in a boat of that size feels terrifyingly fast.

Outboards and bike engines aren’t very comparable. Pushing a boat through water is significantly harder that pushing a rolling chassis through air. So the outboards tend to be designed with a lower horsepower per CC than a bike. For example my 25hp engine is a 430cc twin. On a bike you’d expect a massively higher HP, but I assume the outboard is designed to deliver the best balance of torque and power to run in that environment.

For most small boats you want a short shaft.

Be aware of weight. My boat and 25hp are a little over 50kg each. That’s right on the limit for what I can safely lift (as a sedentary middle-aged bloke). I can move them around ok, but always use a trolley to move them any distance. The 6hp is 27kg which is an easy one-hand carry.

These days the sweet spot for a small inflatable boat engine seems to be the modern Japanese 20hp 4T engines. They weigh in at round 47kg, sip fuel and are virtually silent at tickover.
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2007 CBF1000-ABS - Commuter heaven | 1994 CBR600FR - Awaiting defibrillation

[stinkwheel]

[MCN]

The shape of the Hull determines what speed an engine can push it through the water.
Adding more horses will just blow the screw off the engine due to cavitation. (Wheel Spin.)
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Disclaimer: The comments above may be predicted text and not necessarily the opinion of MCN.

[Nobby the Bastard]

Hull speed, but when it's designed to go up on plane the calcs change entirely between before and after.
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trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Sprint ST 1050

[MCN]