Tohatsu 9.8 2 stroke long shaft

[AJ.]

Hi all,

I have got my hands on a 2007 model, for use as an aux on the RC when I am not in convoy with other ribnetters.

But now I am thinking about using it on a SIB either as a tender when the RC is on a mooring or just blasting around along the shoreline, so I am looking for something small <3m.

My questions are:

How would the SIB get on with the long shaft?
Could I bolt on the transom a piece of marine ply to lift the engine up?
Any recommendations make model for a cheap (second hand £300) small SIB such as quicksilver 240 airdeck?

As always appreciate your advise

Alex

[m chappelow]

I use a long shaft on my sib ,

Down side is with the Tohasu they have a tendency to spray a bit of water up the leg & into the boat in most cases ,
I got around the spray thing by tie wrapping a shaped block of wood to the flat on the leg & made a couple of spray deflector/ shield that also cable tie on.
You could lift the engine up on a peice of wood but its not worth , unless you bolt a higher board on The transom .

You will loose a few knots top end speed & apart from having about 6 inches less drought/depth of water than a short shaft ,you will also have to lean 6 inches further out to clear the propeller if you get a plaggy bag caught up in it .

One big advantage is that if on lumpy sea ,as the the prop is that bit lower in the water it is less likely to airate, and you can keep the power on .

[slate1234]

Hi I use a 6hp johnson (longshaft) and mercury 4.5hp (longshaft) I think a shortshaft would be better but money is a big factor, I dont know whether to sell both mine and get a 9.8 tohasu as they are easily converted to a 15hp

[Downhilldai]

Originally Posted by slate1234

I dont know whether to sell both mine and get a 9.8 tohasu as they are easily converted to a 15hp

How do you do that, then?

[slate1234]

do a search on iboats I belive its just the throttle cam you need to change

[willk]

Slate1234 - you're thinking of the Tohatsu 9.9hp. DHD is a keen fisherman

[slate1234]

willk sorry you are correct it is the 9.9 and you may of just saved me buying a 9.8 cheers mate, the 6hp johnson i have has a restrictor plate on the inlet maifold and is the same as the 8hp but I'm not sure if I have to advance the timeing

[Locozodiac]

Tohatsu 9.8 and 9.9 are completely different animals, First is 170 CC and second is 250 CC. A 9.8 long shaft with a 240 mtr sib is a very bad combination. Too much tail and hull drag. After goofin around for a while will bore you soon, don't waste you money on small size sibs...

Better go a bit upwards, at least a 3 mt sib, can place a 5" engine mount or add same height wooden shim screwed to transom if wanting to use a long shaft engine. If Tohatsu is not correctly height seated on transom will have excessive splash issues...

Happy Boating

[AJ.]

Really grateful for everyone taking the trouble to respond.

So to summarise so i have this clear in my head some people do use a longshaft on their SIB but this does result in lower top end and unwanted splash black due to the hight of the prop. Does the long shaft also affect handling/stability assume the SIB may wheelie greater with the longshaft. Once on the plane would there be any adverse handling apart from a load of water spraying over the transom?

With regards to using a <3m SIB I have read which surprised me (but I am a newbie) that the shorter the SIB can result in it taking longer to get on the plane? As I have a bigger boat I liked the idea of something small will the 9.8 have problems getting a <3m on the plane with 1 or 2 people? 24stone combined and yes I am carrying a bit of timber at the moment!

Again responses greatly received

[AJ.]

Originally Posted by AJ.

Really grateful for everyone taking the trouble to respond.

So to summarise so i have this clear in my head some people do use a longshaft on their SIB but this does result in lower top end and unwanted splash black due to the hight of the prop. Does the long shaft also affect handling/stability assume the SIB may wheelie greater with the longshaft. Once on the plane would there be any adverse handling apart from a load of water spraying over the transom?

With regards to using a <3m SIB I have read which surprised me (but I am a newbie) that the shorter the SIB can result in it taking longer to get on the plane? As I have a bigger boat I liked the idea of something small will the 9.8 have problems getting a <3m on the plane with 1 or 2 people? 24stone combined and yes I am carrying a bit of timber at the moment!

Again responses greatly received

Anyone out there?

[Locozodiac]

A smaller engine will move better a larger boat than a shorter one, depending on your overall weight, could be applied to planing issues too. If usinha long shaft on a short shaft transom at full wot will have so much water splashing inside deck that you could use it as a summer pool...

The splash is produced because water flow is hitting and smashing the non cutting tail edge.

Happy Boating

[slate1234]

I'm a bit lost here I use a 3m sib and 6hp longshaft johnson, but I don't get water splashing into the boat, I would like a shortshat engine but for now I have to use what I have so how much should I raise my engine on the transom
slate

[m chappelow]

Originally Posted by slate1234

I'm a bit lost here I use a 3m sib and 6hp longshaft johnson, but I don't get water splashing into the boat, I would like a shortshat engine but for now I have to use what I have so how much should I raise my engine on the transom
slate

It's the shape of the leg on the Tohatsus that causes the splash back most other engine makers have different leg profiles and don't have problems
, there is a flat on the leg casting thats normally above the waterline that causes the splash everything else is pointy,

Mine only splashes back at displacement speed when up on the plane the boat lifts up so the flow of water then clears the flat part and it reduces the spray
, I fill in the flat in with a shaped block of wood and hold it in position with tie wraps.
Saw on a post a few weeks back about using foam pipe lagging slid on the top edge of the transom that helped someone .
I did make some spray deflectors that tie wrapped on to the leg out of thick sheet rubber something like a set of Doel fins .

[Ribtecer]

Originally Posted by m chappelow

It's the shape of the leg on the Tohatsus that causes the splash back most other engine makers have different leg profiles and don't have problems
, there is a flat on the leg casting thats normally above the waterline that causes the splash everything else is pointy,

Mine only splashes back at displacement speed when up on the plane the boat lifts up so the flow of water then clears the flat part and it reduces the spray
, I fill in the flat in with a shaped block of wood and hold it in position with tie wraps.
Saw on a post a few weeks back about using foam pipe lagging slid on the top edge of the transom that helped someone .
I did make some spray deflectors that tie wrapped on to the leg out of thick sheet rubber something like a set of Doel fins .

That is really interesting, I thought it was to do with the cavitation plates, I have just had a look at mine and low and behold, a flat slab on the front of the leg.

Does your block of wood really stop the splash back? If so i'm of to the patent office tomorrow, its a brilliant idea. Thanks

Ribtecer...

[EnglishLes]

Too late to patent - already been publicised.

[Locozodiac]

Tohatsu compared to Yam is a natural water splasher, it's their particular tail shape design, most portable models have their gear shift rod passing through the non edge portion, that's where the splash is produced at speed/plane. A 39-40 cm keel/transom height is mandatory to solve the problem forever. As all sibs don't have same diam tubes, a trial and error water test must be done to find the sweet height spot.

Happy Boating

[Nightfisher]

Hi all,
Seems to me the optimum engine placement on the transom is where the anticavitation plate is 3/4" Below the centre bottom of hull. Raising the top of the transom is not a hard thing to do to achieve the proper anticavitation-plate location. I know as I raised my transom 1 1/2". However, raising the sailing-boat long shaft type may be too much, but I would think it can still be raised enough to avoid the engine's flat spot area?

[Locozodiac]

On a sailboat at non planing speeds not a real issue with that, the problems starts when trying to plane a sib/rib and engine is not correct height seated specially when using Tohatsu, Nissan, Mariner, Mercury portables, last 3 rebadged Tohatsu's.

Happy Boating

[Nightfisher]

Hi all, Wasn't refering to Sailboating and the engine. Was refering to the general leg-extension size.. quite long compared normal long-shaft engines.

[m chappelow]

Originally Posted by Nightfisher

Hi all, Wasn't refering to Sailboating and the engine. Was refering to the general leg-extension size.. quite long compared normal long-shaft engines.

Some engine manufacturers do an Exra /Ultra long shaft leg or saildrive for displacement sailboats & yachts or where i the propeller will airate or come right out of the water with the yawning action of a displacement boat going up and down in waves .

Some also have a lower gear reduction in the gearbox so that it can take a slightly larger or multi blade/ fan type propeller or have a finer pitch for pushing displacement or heavier boats with high transoms ,.where stopping power is more important than high speed .

Think they are classed about 5 inches longer than a normal long shaft
Short 15 inch
Long 20 inch
Extra/ultra. 25 inch .

First rescue I did was to an old couple who had a yacht with an extra long shaft engine the old type shear pin had snapped on the prop
he couldn't reach out far enough to replace the shear pin & he couldn't get the engine into the boat as he had security bolts instead of clamp screws .