Yamato Cooling

[Flatiron]

11 years later, newest model Yamato same problem, very very Discouraging to a new guy just getting into the sport

[Big Don]

would not a more simpler solution to the "cooling problems" related to the 302's, to just allow the inlet hole in the exhaust snout to be opened up more, versus adding a pickup, which will slow you down? Just amend the dimensions for the hole.........

I agree....but someone need to do just that, drill theirs bigger and test. Than get the test data to the SORC or come to LA with it so the SORC has facts to make decisions on. What if drilling the hole bigger leads to some other problem....Don't know what... but that is the problem with the SORC, most of the time they don't have the data so they are not willing to just make decisions.

[mercguy]

cooling modification...........

would not a more simpler solution to the "cooling problems" related to the 302's, to just allow the inlet hole in the exhaust snout to be opened up more, versus adding a pickup, which will slow you down? Just amend the dimensions for the hole.........

[bill boyes]

Matt. Very true. We use a Digatron head temp meter on the hydro. If it gets to 425 degrees you are in the RED zone. Fact is we have not stuck a motor since we started using one.

[Matt Dagostino]

Rich O.

A little advice..........Testing and racing conditions vary greatly. Chances are you will be able to raise the Yamato 102,80,or 302 to a height that may be fine testing but not work under race conditions. You have to keep an eye on the water pumping at a race and possibly have to lower the motor to be 'raceable' in rough race water. A lot of guys burn motors up by not making the adjustment at the races!

J-Dad

[bill boyes]

I sent a BIG thank you to all who responded,But somehow screwed up,it never appeared.
I now understand the dynamics of whats going on,and why.If it wasn't for YAMATO,we would be where?I guess my remaining question would be,what was the factory YAMATO prop specs?I guess it was all the same for all the racers...What was the Diameter and pitch?
After all these years,it looks like the 302 is a turkey?What makes it an also ran?
Many thanks to all who responded...this is really interesting too!
Anybody like to discuss the black art of propellors?


Thanks guys!
Rich Oliver

The 302 is NOT a turkey.

[jsilvestri]

I'll agree that there are many ways to make the 302 pump water better. Look at how the exhaust cover routes the water, and how you have you discharge hoses routed. Also, take a look at the inside diameter of your discharge hoses. Bigger inside diameter discharge hoses helps keep the motor from creating a vapor lock when the engine isn't pumping that well.

I do think that a lot of guys look at the height of the propeller shaft correctly. You should think about the height of the propeller shaft when you are racing. If you have a boat that airs out really well from front to back then your propeller shaft height is higher than when racing a boat that does not air out well at the transom. This makes a big difference when wanting to pump water all of the time.

[Rich Oliver]

Yamato cooling

I sent a BIG thank you to all who responded,But somehow screwed up,it never appeared.
I now understand the dynamics of whats going on,and why.If it wasn't for YAMATO,we would be where?I guess my remaining question would be,what was the factory YAMATO prop specs?I guess it was all the same for all the racers...What was the Diameter and pitch?
After all these years,it looks like the 302 is a turkey?What makes it an also ran?
Many thanks to all who responded...this is really interesting too!
Anybody like to discuss the black art of propellors?


Thanks guys!
Rich Oliver

[Al Peffley]

Side Note

As a side note about propellers, cooling, and Yamatos. The second year I went to Depue the Yamato team brought a pro Pugh "replica" boat to the Nationals race and a professional factory driver (with rising sun ascot and all new driving equipment!). The factory team of engineers and crew technicians knew their motors better than we did, with the exception of our "special modifications" to gearboxes, blueprinting, balancing, some shaved heads to APBA minimum "specs" on the 102's and new 302's, ...and our wide variety of props. They were amazed at the speed we got out of their motors, and how high we run them. They spent days trying to get propeller information out of the US racers, with no success, crashed in testing (driver error) , and did not place in the final heat. A few years later they learned about the setup changes we made and our high performance prop sources, and they came back with a new driver to place (I think second) in 350 ccH! I didn't ask them if they had cooling problems in testing... All I know is my 250cc engine steams worse than my 102's, and I have gone to moly-coated pistons to reduce the over-heating effects!

Semper Fi!
Al Peffley
15-R/R-25

Look at how the exhaust cover routes the water, and how you have you discharge hoses routed. Also, take a look at the inside diameter of your discharge hoses. Bigger inside diameter discharge hoses helps keep the motor from creating a vapor lock when the engine isn't pumping that well.

What do you mean by the inside diameter? Which size hose should be used?

[Rich Oliver]

Yamato cooling

Ok,Now I get it..and thank you all for your response.I really appreciate it!
Rich

[HYDRO21Z]

never tried

Dennis,
After the height restriction... Did you have to lower the prop to stay legal? Or are you able to pump/cool at less than 1/2" deep?
Larry

Larry,
I have never tested above the 1/2" height.
Always ran the telltale hoses up to the cockpit so I could see the amount of
water being pumped.
Its been a long time so I don't recall if I ever tested higher than the 1/2".
Was more concerned with speed than water pumping, so I really only paid attention that water was coming out at different set ups.
Dennis 21Z

[Jack Stotts]

The last few posts on this subject have been superb. Thanks to both posters for sharing their knowledge on the 302 cooling issue. This just confirms that boat racers are for real when it comes to helping each other. Thanks for some really informative facts.

[reed28n]

prop

The height and prop going together is excellent point, we have had wheels that don't like the 1/2" you need to run them lower and they are excellent performers. I also believe Joel Wiegel has won many races and does not challenge the height limit.

[hydroplay]

The only major APBA CSH race won with a Yamato 302 was a Winternationals victory in Bakersfield CA by Brian Palmquist. It was my rig and was set with the propshaft center level with the bottom and with a fuel pump instead of the gravity system. I don't know the exact year- maybe 2000 or 2001. I also won an AOF CSH Nationals, beating all their 102s and 202s, with that set up. Yamatos can run high if you do your homework and pay attention to all the rules. We found a heat gauge was indespensible to get to this extreme. We ran a temp probe under the top spark plug and watched it during racing. The motor gets hotter each lap and it is much more critical on the 3rd lap to watch it. We also laugh at guys who run fast before the start. We found the 302 will tolerate 400+ degrees at the end of the race but then you have to immediately come off plane and plane off again to get cool water back into the motor. We have finished heats at 417 but started to scuff or stick pistons at 420. Good oil probably gives some additional cushion here. A lightly scuffed piston can be sanded and reused but a stuck one is junk. A lot of 302s have minor exhaust leaks which can limit water pumping when the available water pressure is low.

Running at 1/2 inch is child's play. We run our 20H and CSH at that height all the time, even starting at that height with a new boat first time out. We'd go higher with OSY but the clubs we race with always have CSH and OSY very close together so there is only time to screw around with weights but not heights too. We did have one thermal failure this year but that was when we put a 302 on at the 102 height

However, this is not to say that this is something everyone else can do with a factory stock motor, a brand X boat, a prop someone let them borrow and a driver who doesn't sit in the boat correctly. It is critical to keep the boat at the same attitude going upwind or downwind.

But running at the maximum height is only a benefit if you have props that work that high. I know a number of guys who can run at 1/2 inch but run lower because they go any faster at 5/8 or 11/16 inch. Its usually not a good idea to pull one factor out of a set up equation and say that's why that guy is so fast. Its generally more a matter of him having all the factors as optimized as possible.