I did get some e-mails from other racers about the 70 CES.
I thought I would post rather than e-mail several people and go back and forth.
I can only relate to my experience with the motor and how we would inspect any motor racing in T class in Ontario Canada.
First there were two UIM inspection sheets numbers 398 and 435 [I think there the numbers].
There are two different blocks. You can tell the later block because it has the mounting blocks for the newer style ignition. The one in this thread is the older block.
The original motor does not have 90 hp carbs. It has the older style 60 and 70 hp small carbs.
The crank, rods and pistons weight 1000 grams
Based on the original Specs from Japan the motor is 70 hp at 6400 RPM.
The compression is 150 psi.
The horsepower curve drops quickly after 6500 rpm. The motor will turn 8000 with very light load. The igniton is a weak link to run the motor a very high rpm over long periods of time.
The bell shaped short tuner helps to get higher rpm on a tunnel, but the stock tuner has more torgue and is equal or better on a V bottom.
The designers in Japan copied the OMC Stinger. The gear case is 1.71 ratio on the CES and 1.76 in the OMC. They both are 15 inch mids, off centre chamber heads, The horsepower curve is raised from 70 hp at 5500 to 70 in the yamaha at 6400 and 75 plus at 6000 in the OMC. Based in prop shaft HP the OMC is a little stronger. The big reason is the weight of the rotating assembly The yamaha is very heavy.
You pin or weld the crank on a CES or any modular crank in a performance application because they shift out of phrase. That changes the timing.
Racers in Europe motors pass inspection. That is their inspection and their business.
In T Class here we decided on a maximum compression rule of 160 psi. The motors are stock and run on pump gas, not super stock. Inspection is first fault, easiest first. Visual is first, next is compression. If it reads over 160 psi your out.
Can this motor run over 100 mph in the kilo on a F4 tunnel? Not in my opinion unless it was on a trailer pulled behind a car.
There is no problem with the T850 records
The T850 UIM records are fine in my view. The kilo is 66 to 67 mph and every few years a racer has tried to break the record. In Canada our yamahas run the same as the UIM boats speed wise. Modified Yamahas on our V hulls have not yet shown to have any advantage over a stock yamaha. They all run the same. Lots of mid range and then flatten out right at 65 mph. It is only on the tunnel where the mods appear to help. Fred's comment in the post above makes sense to T boat racers. Our motors in stock form run below 7000, so we do not have the problems the F4 racers get.
Now if you want to talk about a motor which you can really get to go on a tunnel. Think 60D. I bet most know little about them. They raced in Japan with close to mod 50 performance out of a small 2 cylinder 80 to 90 hp at 7500 rpm.
I had a few people message me about these motors
Now if you want to talk about a motor which you can really get to go on a tunnel. Think 60D. I bet most know little about them. They raced in Japan with close to mod 50 performance out of a small 2 cylinder 80 to 90 hp at 7500 rpm.[/QUOTE]
In early 90's they raced a mod class in Japan. Simple rules, motor had to be 2 cylinder mods unlimited. The boat was a tunnel about the size of a Sport C [13']. Boat, motor and driver approximately 500 to 550 lbs. They used 15 inch mids. Suzuki and Yamaha were strong in the class. Yamaha used a motor similar to the 48,55,60 mariner/yamahas.
The yamaha was a 60D.Great motor to mod, Steel crank, twin carbs, light weight etc. The motor is basically 2/3's of the 90 hp Yamaha. They we getting big horsepower and 100 mph speeds. Very dangerous in a 13 ft boat. Take a look at the exhaust chambers on a fishing model of this motor, you can see they likely made expansion chambers in the race version that fit inside the mid.
Yamaha did send me a spec sheet to modify my 90 yamaha and said the motor would make 120 hp and last. I gave the specs to Jon at Hydro Tec. He said there was no way the motor would make 120 hp by those specs and only 150 lbs compression. He built the motor and phoned me after having the motor on the dyno, he called to tell me it didn't make 120 hp. It only made 119.6 hp at 6500 and over 100 hp at 7500. He then asked if it was OK if they used the specs for other customer motors. He has and I still have my motor 10 years later and it still has not broke. I only use this as an example to show the knowledge yamaha had about these motors and Yamaha said they were not into outboard race motors.
If Yamaha and Suzuki ever decided to go and build race outboards, Mercury better move aside. Look what happened when they got into motorcycle racing.