2008 tohatsu 25hp to 30hp questions

[Filthyphil]

Hi I am new here and have read about a simple gasket upgrade as the standard gasket seems to be blocking off 50percent of inlet
anyone have part number
And is there anything else needed
I'm just after a bit more top end speed to get me up n going
Any help would be awesome

 

[pvanv]

What is your model?

 

[Filthyphil]

2008 Merc seapro 25hp tohatsu motor

 

[pvanv]

IF it is a Tohatsu M30A4 2-stroke carbed powerhead, use

346020111M

GASKET

$7.67

You also need to adjust timing. Sea Rider has done a few of these.

In the US, Tohatsu 30s were all 4-strokes by then.

 

[Filthyphil]

Would it cost much for a shop to adjust timing

 

[pvanv]

Do it yourself... Less than an hour for sure.

 

[Sea Rider]

Save the money DIY. Some dealers won't do upgrade conversions due to legal issues, Thst's running a 30 HP motor with a 25 HP cowl. When the gasket has been swapped. Need to know if the timing mark stopst at 20 or at 25 deg, and the distance amount the white roller has traveled on the cam. First pic is 25 HP, second one is 30 HP motors.

The adjustment is very simple :.

-Move the throttle grip to minimum (turtle side) move gear lever to forward. Full throttle the grip, check if the white carb roller stops on the groove of the cam or at the fardest end to know if at 25 oe 30 deg. Without releasing the throttle grip.



In reality it's a simple carb and timing synch adjustment...

Happy Boating

 

[Filthyphil]

Ok so as of now have 25hp carb gasket
full throttle is is open as per 2nd pic 30hp?
And timing set at 20 degrees

 

[Filthyphil]

Full throttle in neutral is first pic
full throttle in fwd is second pic

 

[Filthyphil]

Is the carb roller going to far for 20deg timing should I wind it back to sit in groove??

 

[Sea Rider]

Both posted pics on post 7 are for 25 and 30 HP motors, both geared forward and running at full throttle. If have matched the roller to rest as in second pic you're half of what needs to be done. Get the new 30HP carb gasket to continue with the new time advance setting.

BTW, which boat model, size, number of passengers is the combo transporting now or plan to transport. This is key to know to achieve the max water performance out of that converted 30 HP motor.

Happy Boating

 

[Filthyphil]

Ok will order new gasket asap.
boat is a 1975 DE HAVILLAND SEABIRD 14ft.
1 - 2 people depending on day
25lt fuel tank
Fishing gear

 

[Sea Rider]

This is the boat you currently have ? Seems light compared to a fiberglass one with same lenght.



Which prop number is stamped on prop body. Is it a 13 pitch ? confirm number before ordering the 30 HP gasket.

Happy Boating

 

[Filthyphil]

Yes that's it
it has wooden floor in middle n front also a 4x4 battery in front but in not too much extra

 

[Filthyphil]

Your all over it mate
9.9x13

 

[Sea Rider]

Your all over it mate
9.9x13

According to my experience as a dealer and boeter as well with those 30 HP motors would recommend to order a Tohatsu OEM 3 blade alum 9.9 x 11 pitch prop. Those motors are being factory delivered way over propped. The factory wot rpm range for said motor is 5200-5800. On a light boat with 2 up motor will lose about 800 wot revs. It's a night/day boating difference with a 11 pitch. Combo will plane much easier along handling extra loads.

Let me know when the carb's gasket and new 11 pitch prop has been installed to continue with the 30 HP time advance synch...

Happy Boating

 

[Filthyphil]

Ok will do thanks for the help

 

[Filthyphil]

Just wanted to ask

With just me in the boat I'm hitting 42kmph at wot.

How much top speed will I loose going to a 11pitch prop?

I'm quiet happy with how quick it gets on the plane just didn't want to loose to much top end.

I have the tachometer coming so I'll see what revs I'm at in wot as soon as it arrives
Also have the 30hp gasket ordered

 

[Sea Rider]

Impossible to know as right now is not known at which wot rpm is the motor revving at. A 30 HP well converted should run faster than just 42 Km/h. My 2 strokes 18 HP Tohatsu runs near 40 Km/h with 2 up at its max wot pm range of 5800.



Complete the entire 30 HP conversion, adjust the time advance, install the tach, make a wot run solo boating and check max wot rpm achieved on flat calm water cond. If current motor is running towards the min rpm range a 11 prop pitch will bump wot revs, increase top speed, need to throttle less optimizing fuel consumption, carry more passengers and motor revving up happily between midddle to upper wot rpm range depending on load.

If you haven't ordered the new 11 pitch prop yet, don't order it till the max wot revs achieved are known...

Happy Boating

 

[Filthyphil]

Thanks so much for your help
is there a link or instructions on how to perform the timing advance