Tohatsu 30hp 4-stroke

[doranj]

I'm using a 3-blade, Aluminum, 10x15 prop on a 2010, 30hp, 4-stroke Tohatsu, mounted on a 1962, 14ft Aluminum StarCraft. The engine weighs in at 172 lbs and I estimate the boat and equipment at 250 lbs. The boat use will be all purpose, including riding, fishing and maybe light skiing (if possible).

The engine at WOT should be turning 5250 - 6250 rpm. With a load of two adults, the current prop is turning 4800 rpm at WOT. The hole shot is very weak and top end trimmed speed is 27 mph. Since the current prop does not meet rpm specs, I'm going to change.

Let me know what you recommend to improve the hole shot and get the rpm in the specified range??? I would like to keep the top end up to at least what I've got now, if not a little better. I am figuring a 3-blade, SS, 10x13 might do it, but I'd like to hear from others with experience. Thanks, Doran

 

[DonHof]

Re: Tohatsu 30hp 4-stroke

Doran,

I have a 14.74 Lund, 30 Merc 4S. The dealer put a 11p on my motor.
With 2 adults full tank of gas, it will run 25 at 5800 rpm. The boat
weight about 540 lbs. It's a little slow to come up on plane.

Don

 

[steelespike]

Re: Tohatsu 30hp 4-stroke

For a 4 stroke to perform well you need to get the rpm closer to the 6,200.
You are technically 1400 rpm off.
I think your a little low on the boat weight Boat alone is probably about 250.
Check a few things. Is the throttle opening all the way at the carb/throttle body.
Is the antivent plate(just above the prop) visable on plane?
If all checks out I think you'll need to go to an 11" prop. to approach the 6200 area.

 

[doranj]

Re: Tohatsu 30hp 4-stroke

OK, I asked for advise and I appreciate your input. I am going to take you both seriously and buy an 11 pitch prop.

My boating experience, up to now, has been with higher horsepower engines and I'm having a hard time accepting that such short pitch props are right. However, not only your advise, but my own analysis tells me that you guys are correct.

I'm going to make an order now, and I'll post the new performance results when the prop comes in.

Thanks again,
Doran

 

[steelespike]

Re: Tohatsu 30hp 4-stroke

That will be interesting to see.

 

[doranj]

Re: Tohatsu 30hp 4-stroke

I installed a new SOLAS Amita-3, 10d x 11p (3 blade aluminum) prop today, and what a difference it made. The first thing I noticed was the much improved power out of the hole. Then, when the boat settled on plane at WOT, the GPS speed indicated 31 mph, an improvement of 4 mph. Finally, the RPM has improved from 4800 to 5900.

That 15p prop was way too much for the 30hp. Additionally, the engine had been quitting when I moved the shifter into forward idle with the 15p, and now with the 11p, that problem is gone also.

I appreciate your help in guiding me to the correct prop for this boat and motor.

Thanks, Doran

 

[steelespike]

Re: Tohatsu 30hp 4-stroke

Its allways great to see results like that.Also helpfull for those looking for prop feedback.