Tohatsu deflection plates

[Chopperbill]

Anyone know why the 8 & 9.8(same family) have 2 deflection plates above the A/V plate? The other portable Tohatsu motors only have one. Just a few other makes have some models that have 2. Reason I ask is I had my motor raised 3/4inch and was throwing water over the transom but when I took the 3/4 shim out it stopped it. Kinda thought it defied the theory that if you are throwing water over the transom your motor is too low in the water. What am I missing here?

 

[Sea Rider]

That model has a special lower unit configuration, usually achieve over transom water splashes if water flow at speed hits the upper leg portion inmediatley above defector plates. If water flow hits between both deflector plates will achieve a back transom splash, not over transom though.

The best lower unit height for any Tohatsu engine is water flow skimming right under def plate located right above lower AV plate. Have you checked as recommended where is your flow passsing right now that doel fin is installed ? If engine is not at a 90° when on plane with well ballanced sib, you're adding extra unwanted drag on doel fin which will slow sib a bit. Fin must ride parallel to water level to cut flow as a cheese. You have already a underpowered 9.8 HP engine which at 5 K of altitude is really working as a 7.5 HP.

So it's a must make a good engine/transom match to count with real world minimum lower unit drag on that 7.5 HP.

Happy Boating

 

[Chopperbill]

With motor raised 3/4 inch (all that I can then run out of transom) I get over the transom splash. With motor resting on transom I get a little back of transom splash. Which is more livable. That's the best up and down I can get without major work. Easy to play with trim. I am curious why this motor model has two deflector plates and no other models do.

 

[Chopperbill]

Emailed Tohatsu USA and asked them. They replied. Confused, mine is short with extra plate and how can a/v plate deflect water if it's under the water? Hello Bill, The motors just have different designs accordingly and the longer motors may have an added plate in some cases. The A/V plate is the lowest and can deflect most water, but the others help in certain applications. It depends on the application and there are various situations that can affect the water spray. Thanks, Alan

 

[Sea Rider]

Not really an tech issue as long lower unti is properly height setaed on transom. Just curious, can you measure distance from lower keet to upper transom in straight line in inches ?

Happy Boating

 

[Chopperbill]

No Title

Top to bottom of transom is15" however keel makes a little turn where it attaches to the transom and turns down about an inch. See picture.

 

[Sea Rider]

Top to bottom of transom is15" however keel makes a little turn where it attaches to the transom and turns down about an inch. See picture.

Post a pic as seen from back transom without engine attached to check the small turm.

Happy Boating