Tohatsu 30hp 2s low speed help

[stevessub]

I'm currently running a tohatsu 30hp 2 stroke 2003 on a 4metre honwave but my top speed is only 25mph, I expected a little more than this, what could be wrong engine only has 20hrs from new and is running a 9.6x13 prop.

[Turbodiesel]

25mph does'nt sound to bad to me!

[LWman]

Have you tried putting the trim pin up a couple of notches? It seemed to make a noticeable difference to mine. Also i take it this is your video i was having a laugh at the other day?

Honwave t40 tohatsu 30hp pulling ringo - YouTube

[TomKat]

check the throttle is opening fully, I have a 30hp Mariner which I understand to be a Tohatsu. I have spent the last few evenings getting the throttle 100% open, tried it out today and easily get 35 knots (with just me in the boat!). The cable/rod did not have enough stroke to fully open the throttle so I bodged a fix and seems to work OK.

[Polwart]

It doesn't sound like its majorly off from what you might expect (I'd have thought you'd get a bit more in that I can get just manage 25 mph lightly loaded with a 20HP on a 4m boat). I'd be surprised if you get much over 30 mph easily. What speed were you expecting?

You might be able get better than you are doing by playing with props, trim, boat load and inflation pressures etc. Starting point for logical improvements is probably to know what RPM you are achieving though.

[C-NUMB]

The rig on this model is slightly longer than on most other engines, at least this was the case on the long rig model. Check the cavitation plate hight compared to lowest point on transom, maybe you need to lift the engine slightly?

[stevessub]

tried lifting the engine up a few notches and found the 3rd one from bottom is the best (25mph) Im starting to think it could be the prop, If i go for a 9.9x14.2 would i gain much. the prop i have at the moment is 9.6x13, and its its second.

[Polwart]

steve, I think C-NUMB is referring to the length rather than the angle. i.e. you could try moving the whole engine up the transom by an inch or so.

As for increasing the prop pitch this might actually make things worse. Without a tacho on there we are all just assuming you are achieving maximum revs. However if you are, the prop is slipping a lot more than I would expect. Before spending a £100 on a new prop I'd be spending £50 on a tiny tach.