Tohatsu 30hp top speed

[Steverob1983]

Local marine shop I have been dealing with has recommended I go for a 10 pitch prop with same diameter and will ship next to to where I am currently on holiday. Trying to get it sorted out while I am here as I have easy access to launch to sea straight across the road. I'll try and check the timing tomorrow before ordering the prop.
Thanks for everyone's help, Really appreciate it.

 

[Sea Rider]

Local Marine Shops can and will sell you anything they want to, the only way to know 100% if a 10 pitch prop will achieve at least middle wot rpm range is by duplicating testing a exact same HP/combo as yours. Other than this is pure speculation.

Assume tach was correctly installed and set to : 2P,1R, to read just 4300 wot revs, right ?

With a 10 prop expect way more than middle wot rpm range, would dare say that OB will rev high. Anyway if going for a OEM 10 prop have seller know that if the prop he blindly recommends revs high he will change it for more pitch, say 11 prop. Post 10 prop results as loaded.

Happy Boating

 

[Steverob1983]

Would it be wise to go for an 11 pitch prop instead then to be safe? Looking to change the prop anyway as it looks very old and has a few dings in it.

 

[Sea Rider]

Can't possibly know without a water trial with any of both pitches. A 11 pitch should put OB closer to middle wot revs than a 10 pitch powering a light Rib which has less hull drag than a Sib.

Personally would go for a OEM 11 pitch powering a light Rib. I have a 450 Mtr Rib, powered with a 2 strokes Tohatsu 18 HP, 3 alum blade 9 pitch prop, Solo boating with 430 Kg. achieved 5600 wot revs from max 5800 factory stated. Changed it to a 8 pitch and the OB over revved + 500 wot revs to 6300.

Tested a 430 Sib with a 30 HP and achieved 4850 wot rpm with 2 up with a 13 pitch prop, ordered a 11 pitch which should increase 800-1000 wot revs to it's max wot rpm range, have not tested it yet though.

Anyway check the possibility with dealer to swap props if in need. Have not answered if tach was set to 2P,1R ?

Happy Boating

 

[Steverob1983]

Sorry. Yes the tech was set right and the OB is on a 3.85m sib. Iv ordered a 10 pitch which will be delivered next day to where we are currently on holiday and will arrive Thursday and if delivered early enough will test Thursday.

 

[Sea Rider]

Did you checked timing advance plate to stop at 25? right at middle of mating surface ? check, adjust before changing new prop.

Happy Boating

 

[Steverob1983]

Yea checked timing. Been for a test run today with 10 pitch on and it sits at 5500 rpm wot. Could only test for about 10 seconds at wot though as it was really choppy. Topped out at 28 mph with me, 2 kids and full kit.

 

[pvanv]

Sounds like you have it dialed-in about perfectly.

 

[Sea Rider]

As loaded, at 5500 wot rpm OB is at middle of the wot range which is good. OB has achieved + 400 wot revs per one less pitch (+1200 wot revs total with 3 less) If OB was not at full grip when tested on choppy water cond expect slight more wot rpm and max speed.

So timing advance was correct at 25?, right ?Just for the record, was that 10 pitch prop a Tohatsu OEM one or any other brand prop ?

Happy Boating

 

[Steverob1983]

No it's not tohatsu oem. It's a solas amita3 prop which seems to have really good reviews.

 

[Sea Rider]

Really doesn't matter which brand you choose, if you test different prop brands with same diam and pitch, all will achieve different wot rpm. Report max wot rpm and speed on flat calm water cond as loaded, will be interesting to see if OB pulls revs bit higher and close to 5850 max wot rpm range.

Happy Boating

 

[Steverob1983]

Bit calmer today. Max rpm I saw was 5550 and max speed 33 mph. Had some fun today with the kids on a ringo which it pulled with no effort at all. Pretty happy with the results from changing the prop as it has nearly doubled my top speed and it's pretty much instant onto plane. Put about 4 hrs on the engine today and about 40-50 mile which has made me realise I really need a centre console as have serious arm ache from tiller control.

 

[Sea Rider]

Personally don't like centre consoles, takes too much needed deck space which is a must have.

If being a 2 piece hull/deck Rib, an excellent idea is to install just a seat & locker aft transom, that way will tiller drive more comfy seated.





Driving seated on tubes while throttling with extended arm on long cruises is really arm & butt tiring.

Happy Boating