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Tohatsu 3.5hp 4str Long Shaft with High Thrust Prop

Mark-1

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22 Sep 2008
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I'm about to buy a new Tohatsu 3.5hp 4str Long Shaft with High Thrust Prop.

Two questions:

Should I be considering something else, if so why?

Are high thrust props worth it? (There no reverse gear.)

TIA.
 

C08

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My personal experiences with so called high thrust 4 blade props on Tohatsu engines is having seen very little difference to standard 3 blade props. "Saildrive" engines which have a higher ratio reduction on the gearbox so swing bigger props than standard engines are a different thing altogether and do have much merit but I do not think the 3.5 is a saildrive engine?
EDIT: One thing the 4 blade high thrust prop was good for was in astern having much more and more controllable thrust particularly at lo revs.
 
Last edited:

Mark-1

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I would go the extra half HP just for the reverse option.. but that's purely down to my (boat) circumstance..
It's a dielema but I value weight and simplicity over reverse gear which I hardly ever use in the marina as things are and next year I'll be on a swinging mooring.
 

LONG_KEELER

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Not an easy decision .

The 4hp model , with reverse, is 26kg which is 7.6kg more , about 3 1/2 bags of sugar. Both seem to have the same tankage, just over 1 ltr Fuel.

Looks like you can swing a bigger prop with the 4hp . Very beneficial for displacement wind and tide bashing.

I take it that it will power a yacht and not a dinghy.
 

Mark-1

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Not an easy decision .

The 4hp model , with reverse, is 26kg which is 7.6kg more , about 3 1/2 bags of sugar. Both seem to have the same tankage, just over 1 ltr Fuel.

Looks like you can swing a bigger prop with the 4hp . Very beneficial for displacement wind and tide bashing.

I take it that it will power a yacht and not a dinghy.
Corribee. Approx 1 ton, but the reverse or not decision is already made. Rightly or wrongly it's 'not'.

The only questions are: is there better lighter engine available new, and is a high thrust prop worth it.
 

Mark-1

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Having the ability to turn engine through 360 degrees negates the need for reverse.
...and on my current engine, which has reverse, that's what I tend to do because it's such a reach for the gear lever.
 

TernVI

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Having the right prop is usually worth it.
If the prop is too coarse and the engine won't rev, the engine becomes a lot less than it's nominal HP.
It might be worth checking whether a variety of props are available.
You might have more choice with a Yamaha?
 

Fimacca

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I have a new tohat 3.5 and used to have a corribee. I used a long 5hp suzuki with saildrive
Depends where you sail, but I would want more thrust...................imho......
 

Mark-1

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I have a new tohat 3.5 and used to have a corribee. I used a long 5hp suzuki with saildrive
Depends where you sail, but I would want more thrust...................imho......
Yeah, I certainly want more thrust, but equally I want to be kind to my back. I never battle into wind and chop so I'll chance it.

What do you think of your Tohatsu 3.5? Leaving aside lack of power for my application are you happy with it? Anything you wish you'd bought instead? Any foibles?
 

Fimacca

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The 3.5 planes my honda airdeck dinghy with just me ! Nice and portable and seems well built. Not used on a displacement boat.
You could always go for a larger 2 stroke if you can find one. Same weight. the tohat twin sparks at 6- 9.9 hp were great machines. I don't know the weights but they are online.
 

Mark-1

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The 3.5 planes my honda airdeck dinghy with just me ! Nice and portable and seems well built. Not used on a displacement boat.
You could always go for a larger 2 stroke if you can find one. Same weight. the tohat twin sparks at 6- 9.9 hp were great machines. I don't know the weights but they are online.
I'd love a 2 stroke but any 2 stroke is going to be a bit long in the tooth. I'm sure there will be excellent ones around but I'm unlikely to find one in the time available. Rebuilding my current one might make sense. (It's a bit rattly so I assume on its last legs.)
 

Boathook

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Surrey & boat in Dorset. Both have pubs
Having the right prop is usually worth it.
If the prop is too coarse and the engine won't rev, the engine becomes a lot less than it's nominal HP.
It might be worth checking whether a variety of props are available.
You might have more choice with a Yamaha?
Yamaha dual thrust prop fits my Honda 30 with a bit of lathe work. As long as the splines are the same you are halfway there.
 
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