Wide full open..

[centrefire]

G'day,
The other afternooon returning from open water, I decided to clear the cobwebs from the manifold of the trust old 30 horse 3 pot Yam.
Holding the throttle wide open for the 5 km river return run to the ramp, I noticed that with the throttle on the stop or 3/4 open produced the same result. The engine sounds the same, boat speed is identical ...nothing changes.
I have a new standard prop and the carbs all open fully.
On a bike, any throttle increase results in additional revs etc.
Is this normal or am I missing something?

[FishHunter]

What rpm is it hitting?
if the carb butterflys open fully are they opening fully at the 3/4 mark or only when the throttle hits the stop?

[propdinger]

there is normally not that much gain in horse power or speed for me with the 40hp or 25hp i have had from 3/4 to full open just abit more noise on the 40hp but no gain in speed just fuel burn but in the 60 hp i get a little bit faster.

[Roughasguts]

Yup that's normal if you wan't to get more revs lose some weight EG: pasengers eskys fuel tanks what you need to do to get more rev's is put weight up forward to get the back of the boat further out the water Or you could sit further forward, raise the motor a notch, play with some trim angles ETC.

Cheers.

[nick-o83]

sorry fishunter, didn't mean to "dislike"!!! finger slipped while scrolling down.

Nick

[centrefire]

Thanks for all the responses, appreciate it.
The butterflys all open fully at the WFO position on the throttle twistgrip.
I guess it's doing the best it can, which is fine for an old grey beard and an equally old Savage 4.3.

Cheers.

[MudRiverDan]

Not knowing much about boats but a little about small engines..

All carbs fully open is full throttle, if full open occurs before the throttle itself it on full it would just be a cable adjustment.

Would be a little different on a boat especially full throttle for 5km of water, the conditions would obviously limit the engine a little, and as mentioned above weight etc.

I have owned a few small motors and usually once moving top speed you are asking for more power from the engine in regards to throttle response.

2c
cheers

[FishHunter]

sorry fishunter, didn't mean to "dislike"!!! finger slipped while scrolling down.

Nick

I was just about to abuse you till I read this :)

[winston]

Centrefire, change the prop to 1" less. I had the same motor on a previous combo and changed to an 11" pitch prop (stainless) and it made a large difference. I have the same motor now and will change to an 11" pitcch unless my fishing buddy looses 50 kg. Cheers Winston.

[centrefire]

Ahh...less pitch,less resistance in the water = more selective reving through to redline . Logical, makes sense to me.
Thanks Winston.