Tohatsu 2stroke 30hp overreving

[WesNewell]

Yes, the exhaust gases are causing the prop to loose grip.

 

[Sea Rider]

Some issues :

Posted pic of the aerating prop shows more turbulence going on at 12 o'clock than a lower 6 o'clock, the prop thurst must be equal on both sides of prop for top effective thrust, trim the motor up one hole for AV plate, prop shaft to run parellel to water surface when on plane at wot.

Is water flow skmiing right under the upper small water deflector plate ? if not will need to rise/lower the motor on transom to chieve that. Must make a visual inspection of what is going on at back of lower leg when fine tuning the lower leg height.

My cousin forgot to install the prop washer, both mating surfaces has been shaved badly, there's a one centimeter gap between prop body and gear case assy, guess what same motor works top with 0 prop aeration whatsoever, the motor has been carefully tarsnsom height matched to perfection, your motor gap is nothing compared to.

Props are usually through hub exhaust ones, but there are over/through hub exgaust props, my cousing has dialed the latter without knowing anything about them. Report you findings with new trim setting. on a wot run on flat calm water cond and correct deck load evenly distribution.

BTW, OEM Tohatsu props are excellent performers, don't understand why the mayority of boaters likes swapping them for other prop brands with same pitch that can dial different wot rpm compared to same OEM props with same pitch.

NOTE : Don't go for a new drive shaft housing assy, test with proper trim and motor height as indicated before..

Happy Boating

 

[jimmbo]

Too bad you didn’t mention the operation without the Thrust washer in the original post... At least the repair is relatively cheap, just the bearing carrier, and a few seals to be replaced. Other gear case designs would require the entire housing to be replaced.

 

[bblagonic]

Too bad you didn’t mention the operation without the Thrust washer in the original post... At least the repair is relatively cheap, just the bearing carrier, and a few seals to be replaced. Other gear case designs would require the entire housing to be replaced.

I've realized it after the investigation, only. My bad.

 

[Faztbullet]

Just replace bearing carrier, install correct thrust washer for prop used.

 

[Faztbullet]

the prop thurst must be equal on both sides of prop for top effective thrust​

No it does not...These "theory's" you must dream up !!! . How does a surfacing prop work as it has 1/2 its blades above water surface. Notice this usage of trim at 1:16 and wake drops as boat airs out..1/2 of the prop is out of water
https://www.youtube.com/watch?v=Of1RY4M8VqM

 

[jimmbo]

He likes to bury the props about 5-6 inches too deep in the water as well

 

[Sea Rider]

No it does not...These "theory's" you must dream up !!! . How does a surfacing prop work as it has 1/2 its blades above water surface. Notice this usage of trim at 1:16 and wake drops as boat airs out..1/2 of the prop is out of water
https://www.youtube.com/watch?v=Of1RY4M8VqM

Hey Faz, when will you end your idiotic video comparisons, what does a manual trim 30 HP motor propped with a OEM standard alum prop has to do with a 40 HP motor running a surface prop whichever that prop model is on a different boat ? Tohatsu motors will aerate badly if prop works that way, the length of the upper to lower plate is much larger on those motors. You don't own nor work with such HP motor brand to know what works best and what doesn't and even dare to make out of this world comparisons against boats and motors, so cut the you know what...

BTW, stop fully or partially quoting my posts or will continue with this endless personal tech confrontation I'm getting tired off...

Happy Boating

 

[Faztbullet]

Che I posted the video to show you are WRONG that prop thrust doesn't not have to have equal on both sides to have thrust...I do this to correct some of the incorrect information you post. I use the videos/pictures as there are thousands of them that contradict the info you state as fact. Not picking on you but at least give a poster the correct information or suggestion..And yes I have worked with Nissans/Tohatsu's before as we was TN largest dealer!!

 

[bblagonic]

Have made a trials this morning.
Before buying the new bearing carrier I made a ring replacing the missing part of the bearing carrier...see attachment

In addition, I have noticed that the original trust washer had the outside diameter bigger than the prop housing by 2mm in radius. I have removed that excess of material. Doing this, the openings for exhaust gases thru the prop are without obstruction.

Everything is back to normal, now. The boat and the motor are performing great. Reached 15kts on rough sea.

Thanks to all of you. Especially to Jimmbo which detected the unusual gap between the lower unit and the prop with possibility of exhaust gases leakage.