Tohatsu anatomy 101.

[jeff55v]

Way back in '05, I dismantled my Bass/Tohatsu powerhead. I had the crankshaft pins welded as per manufacturer recommendations.
While I had the powerhead apart, I took a few photos of the inner workings. I thought maybe someone would like to see the inside of one of these. I had posted a few of these photos here at HR before. I now updated my website with a page dedicated to this photo shoot. Just in case folks wanted to study this sort of thing over the winter months.


http://jeff55v.tripod.com/id33.html

Let me know what you think. But go easy on me, I don't know anything about web page design etc.

[DougMc]

Way back in '05, I dismantled my Bass/Tohatsu powerhead. I had the crankshaft pins welded as per manufacturer recommendations.
While I had the powerhead apart, I took a few photos of the inner workings. I thought maybe someone would like to see the inside of one of these. I had posted a few of these photos here at HR before. I now updated my website with a page dedicated to this photo shoot. Just in case folks wanted to study this sort of thing over the winter months.


http://jeff55v.tripod.com/id33.html

Let me know what you think. But go easy on me, I don't know anything about web page design etc.

Why do the pins need to be welded?

[sam]

Why do the pins need to be welded?

Pressed together crank sections can rotate out of alignment and cause out of balance/vibration problems. Both the pins and holes they are pressed into are smooth.

Welding them locks them into position, they never come out of correct alignment.

[pro350hydro]

Pressed together crank sections can rotate out of alignment and cause out of balance/vibration problems. Both the pins and holes they are pressed into are smooth.

Welding them locks them into position, they never come out of correct alignment.

This is a standard practice on larger displacement motors with press togethor cranks such as the tohatsu and the Pro Motors to keep them from twisting. I have seen cranks twist in pro motors on the beach with no load applied to them at all.

[Jeff Akers]

I like the site Jeff, It looks great!

[nbass]

Nice Job

Jeff, thanks for buy a Bass Tohatsu and for providing a technical view, nice site. I wish there were more technical discussions and sharing of information on all engines and subjects.

Most of the Tohatsu racers choose not to weld the crank pins. I know of one racer that had a crank slip and it only cost him $150 to get it repaired and welded through our recommended supplier. I personally can go either way, try it and if needed weld it, or just take care of it before it becomes a race day problem. I understand from Fast Fred that the Tohatsu cranks have improved over the earlier versions and welding may not be as critical as before. We have one advantage over the rubber boat racers in that we are not trying to swing a large propeller that releases and grabs hard as the boat hops along. However, spin-outs and rough treatment still has its risks of twisting the crank.
Neil Bass

[Fast Fred]

Pressed together crank sections can rotate out of alignment and cause out of balance/vibration problems. Both the pins and holes they are pressed into are smooth.

Welding them locks them into position, they never come out of correct alignment.

No, what happens is the mains turn on the Hot-su's, and the crank loses it's timin. on the big Yama the top snout of the crank will lose it,s press and walks off the top wrist pin and cuts the case wide open that what happens

[nbass]

Enlightening

I think we should have a Fast Fred tech section. Fred has helped us with several issues when we began the Tohatsu project. Thanks Fred.
Neil Bass

[99R]

The crank on the Tohatsu magicaly gets longer trust me.

[jeff55v]

Pin welding

I opted to weld my crankshaft pins after careful consideration. I really didn't want to take my brand new engine apart. But, I invested in this motor because I plan to race it for a long time. I figured the effort invested in welding the crank pins would be well worth it. I kinda wanted to learn more about the insides of this motor anyway.
I found the engine was actually pretty easy to take apart and reassemble. By the way, after I bought this motor, I immediatly invested $50 in the Tohatsu service manual from my local Nissan dealer. Always a good thing to have on hand.
I was told by many that the water conditions at Top O' this past year were some of the most favorable conditions they'd seen in quite a while. Maybe they were pulling my leg, I dunno. But, I remember racing on Sunday thru what seemed to me like endless rough water. I wanted so badly to turn around just to look at my engine. I found it impossible to take my eyes off the water in front of my boat, even for an instant! I raced for what seemed like an eternity of pounding rough water not knowing if my engine was even still tightly attached to the boat!
My engine performed flawlessly! Thanks in part to Mike Ross's advice given to me telling me to "Locktite EVERYTHING!" I was also glad to have the piece of mind knowing that my crankshaft was welded.

[Richard K.C. Mo.]

Stock!!!?

Just doesn't sound like a stock class to me ,internal Mods. and all.
Stock mercs in d class turn about the same .

Would more internal mods help the stock mercs?
Maybe new motors outway the stock part of it?
Richard

[seanp3]

Is welding the crank a "mod" or just a fix to a problem?

[Richard K.C. Mo.]

Fix a new motor?

Anyways , seems to be a lot of old mercs out there, lot cheaper than $5K.
If nothing else rpm fix, eh.
Richard

Is welding the crank a "mod" or just a fix to a problem?

[Fast Fred]

think of it like fiber reeds, or cheap insurance

my self, on the pin vs the weld, i like the welded idea best, cuzz of some things,
did not like the idea of drillin the crank for pins, takin away crank meat to make it stronger just did not hold up against a weld, and it sure worked good for them Drag bike cranks, new is the best tine to get them done

look close, Dead on, less than .001 deflection
[img=http://img234.imageshack.us/img234/2025/crank2wp0.th.jpg]

[Fast Fred]

like a row of coins just like that seems to work best, ready for NitroMethane