321 Motors in non-sealed classes overheating

[Harold8]

So, an Un shaped foot, with a two blade prop, run at 1 3/8 in the 300 class, has no overheating problem, but a shaped foot with a three blade prop at 3/4 has an overheating problem in CSH. Do I have this right or am I missing something?

[Ericwienczak]

Yes you have it correct. We ran shaved foot or 20 and c and we were overheating (running almost an inch deeper than max height trying to keep the motor cool)

No issues with stock foot at max 300 height

[Harold8]

So rather than an internal tower problem, wouldn't you think that changing the contour of the foot is changing the water flow to the pick up? Just wondering.

[GrandpaRacer]

I think it is time to solve the Yamato cooling problems for all versions of the engine. The SORC should consider a rule change to fix this only weakness Yamatos have. Every other motor we race cools just fine and those owners are not spending money each year because their engine over heated. The rule should allow cooling with water anyway you want but the Billy hole must remain open.

[stockc]

AMEN... lets chat next race

[Ram4x4]

Looking at various pictures of the 302 and the 321, it looks like the stock foot is shaped the same. Unless the intake hole has been moved or changed, it doesn't make sense that the 321 overheats because of the foot.

Will a 302 foot fit a 321? If so, maybe someone could mount a shaped 302 foot to a 321 and see what happens?

[Ram4x4]

So if the foot is the same, then it has to be something in the tower. The 302 runs fine with the shaped foot, so something in the tower is preventing good flow.

[GrandpaRacer]

Or heating the water before it gets to the power head.

[Ram4x4]

But then wouldn't it do the same with the stock shaped foot?

Since the water is pressure fed by forward movement, does shaping the foot lower the pressure of the incoming water? Something in the tower is restricting or slowing the flow. Is the water passage through the new tower larger in volume and needs more pressure to get the water through?

[65R]

Who cares why, Just change the rules to allow any Yamato to cool anyway you want. We are restricted by height anyways

[Ram4x4]

Well, knowing why is kind of important for figuring out the best fix don't ya think?

[HydroKyle93R]

Just in example, I was running a 302 at Cullaby Lake last weekend. It was just under 70 degrees air temperature, sea level, mile course with long chutes, CSH at 3/4" below the bottom of the boat. My cylinder head temperature sensor was reading over 420 degrees by the last lap. It makes me a little nervous to run that hot, when I've stuck a motor at 430. Several times.

Piston - (oversized) $130
Rings - (oversized) $32 each
Gaskets - $30

Potential to not overheat - Priceless.
For everything else, there's hard earned money.

[65R]

I've been racing for three years with a 302. I constantly watch engine temp and change setup if needed. In three years I've had to rebuild my motor, probably 8 times because of over heating.

[Lee Sutter]

I'm looking for some logic on this issue. We race water cooled engines on water and they overheat. All the other stock engines have water pumps - not Yamato. Why, because they run the Yamato's in Japan buried in the water and they cool just fine. However, if you want to run the Yamato engine higher on the transom to go faster, like we do, they might overheat and damage the engine. Everybody loses except the people involved in the fix.
Can this be fixed? Yes! What would you do? Fix the 321 and 302 so it cools and submit a proposal to APBA SORC for consideration. How much would it cost the racer? Zero to $50.00. Would you lower the engine? No .Do I need new props? No. Who Wins? THE RACER!!!!
JUST COOL IT!

[Ram4x4]

Well, then I'm going to chalk it up to me being a second year noob. Until the 321 came on the scene here recently I don't recall seeing any discussions here about any of the Yamatos overheating while running at less than an inch or with a shaped foot, especially not someone complaining about burning up engines a couple times a year.

If the 102 or 302 is also overheating at less than an inch depth, then it seems this isn't a 321 problem, but an overall Yamato problem in general.

If it is due to running too shallow of depth, then that's the issue. If the engine wasn't designed to do that and we're doing it, well, there ya go.

So, if this is indeed the case, what then is the best fix? Increase the intake hole diameter? Install a pump? What?

[GrandpaRacer]

Yes, this has been an issue with 102 and 302s, maybe less than the current 321 but an issue for sure. It can be very frustrating and very expensive. We don't know the best fix ( cheap and easy) but there are many options to test.
John Adams

[Adams52R]

Run a water pickup line straight to the back of the block just the guys in 500CCH do. Easy and inexpensive fix.

[Ram4x4]

That does sound easy and inexpensive. Why would something like that be made "illegal" to begin with?

[Team B&H]

Back in the day when I was serious about beating the 102s with the slower 302, it took some doing and a number of pistons but I did eventually get the 302 to run and survive with the center of the propshaft level with the bottom of the boat. And it complied explicitly with the rule book and inspection manual. We could race and finish with top cylinder head temps of 417 but would stick at 420. But then the authorities couldn't figure out how we could do that and nobody else could so they embarked on the forever lower pattern as a non-voteable "safety" rule when it was clearly intended to be a performance limiter.

I have only a couple hours recently with a 321 and two 302s that were aimed at the 300 class height. The motors all did run OK on the boat but the 321 did run hot on the test wheel. We figured the water pump was just picking up cavitated water from the test wheel but it seemed to do the same thing even when moved away but the carb was pretty well set by then. It did seem that it got hot but had solid streams of water from both water outlets. But we just moved on to actual runs on the boat. All this makes me more inquisitive! More questions than answers right now.

[pav225]

Have people tried running the 321 lower? How much lower do you need to go to have it cool enough?

[daveracerdsh]

I agree with John Adam's post. CSH, 20sshe, 300ssh are SUPPOSED to be stock classes.....minimal money required to keep motors running etc. What are we telling new people getting into the sport when motors they purchase, thinking they will not have to rebuild them for a while, burn a piston after first race. I could go on.....but I do not run a Yamato. Dave

[Ram4x4]

All I can say is that since driver school, driving borrowed boats and the school's boats last year and now my own with a 102, no one has ever pointed out that Yamatos are prone to overheat and that care needs to be taken to watch them closely. I was fully under the impression that the new 321 was the only one having issues.

Not pointing any fingers are trying to blame anyone, but if this has been an issue since Yamatos came on the scene, it would certainly be good info to discuss with newbies to make them aware. Cylinder head temp gauges aren't terribly expensive.

[hydroracer25]

Dane,
While there has been issues in the past with the Y80, Y102 and Y302 pumping it is typically at the 1/2" propshaft below the bottom of the boat. With the 3/4" limit on the CSH class there have been very few (if any issues) that I have heard of. You still run the chance in the 20SSH class with any engine of over heating once you get close to that 1/2" area. The 321 is new to Stock Outboard this year and issues appear to be in the "non-300" classes. As for letting you know of any issues with regards to cooling, when you purchased your CSH/102 rig last fall I wouldn't have thought to tell you about any cooling issues since the CSH at 3/4" doesn't have any. See you soon.

[Ram4x4]

Understood, but I did run it twice at Franklin in 20, fortunately I left it at 3/4". I've since decided to enter 500 mod with it instead of 20 until I have time and money to play with different props and tuning to run 20 with the restrictor. As it is now, just popping in the restrictor and leaving the C prop on dogs it down too much to think about being competitive at all.

Still going to add a temp gauge if for no other reason than to see what it is actually running at. I'd rather spend $50 for that than the costs of a rebuild, just in case.

[mrlou40]

Well John, for years I have been waiting for someone to come out and say it, it is quite simple though Ric and the other suppliers of Yamato parts might not be happy it is time for the SORC to enlarge the water pick up on the tower. They need to do testing with the 102-202-302 and now the 321. The heights seem to be safe but when at any given race they have to pull off during the race just to cool and not hurt the motor something needs to change as it has needed to for years now. We seem to be at a point that our "new" motor has issues and to go forward this needs to be addressed.

My 2 cents

[crfabbro2F]

I have a 302 tower I will donate to anyone wanting to experiment.

[Ram4x4]

Well, this has all certainly put some things into perspective. Being that I just bought my first boat end of last year and have run it in its first two races this year, I am now concerned about over heating! If I burn a motor, I'll definitely be out for a while as I'm not in a position to afford rebuilding an engine right now.

I think I'm going to go invest in a head temp gauge just to get an idea of what my 102 is doing.