250cc Engine Questions

[leehome9602]

Hi everyone

I'm new to the sport and trying to get set up. Looking for some advice on my engine. I bought the engine with a 13ft hydro and don't really know much about it.
I was told its a twin Yamaha 250 that runs on methanol. My main problem is trying to figure out the best lower unit/gear ratio to use. I understand everyone has there own set up and preference, but any help would be greatly appreciated.

I attached some pics of the engine for additional reference.

Thanks
Lee

http://images.craigslist.org/5N75I35...f0805a1875.jpg
http://images.craigslist.org/5E35T15...4ca5561d9d.jpg
http://images.craigslist.org/5Nb5Ib5...28d8871cd9.jpg

[David Weaver]

2 Primary Choices

11:15 - VRP, GRM (Rossi) or Konny

12:16 - Yamato (if you can find) and maybe GRM.

Suggest that you begin with 11:15. Be diligent on changing oil and checking condition of gears and bearings.

Could not see photo's.

[DiGia54D]

I was able to see the photo's... Thats a Yamato 250cc not yamaha. There are a couple of people oh here that have Parts for those or can get them on this site. What part of the country are you in? if you post a photo of the boat also..the guys on here probably can give you all the history on it.
I wish you luck, I brought a 250 rig and will be starting this class next season.

[nicf14]

It is a Yamaha, it was mine. 12:15 is what you need.

Call me 407-947-8692

[JBM]

Did Yamaha factory build racing motors? Or, is this a custom job?

[leehome9602]

Thanks for all the help guys...like i said i really know nothing about this type of motor

[bill van steenwyk]

What you have is...........

Did Yamaha factory build racing motors? Or, is this a custom job?

........ a custom built engine using Yamaha cylinders from probably a motocross or road racing bike, and a crank built up from probably Yamaha parts put together so as to allow both cylinders to fire at the same time instead of alternately as it was originally designed. These type engines have been built for many, many years, by folks who have the talent and equipment to do so. They have generally been built, as is the case with your engine, by using components from high performance engines of other types, making from scratch a crankcase, usually by machining from a billet of aluminum, and then assembling the parts into a very competitive piece of racing equipment.

Reasons for this type of effort have gone from economic reasons, i.e. purpose built for racing engines by others too expensive, or other reasons such as wanting to compete with something no one else has, the satisfaction of building something competitive with your own hands, and sometimes the profit motive or selling them in quantity to other racers. The last reason very seldom happens, or as the saying goes, "if you want to be a millionaire, start building racing engines with five million dollars".

Among them have been members of the Eldridge family, of which the person who replied to your post with the information it was his engine, is one. Among others who have done this in the past with not only cylinders from other applications but other components and even complete engines from scratch are Kay Harrison, his Father Milly with the Harrison Anzani's in the 60's, Joe Michaletti (SP?) with I think Yamaha cylinders on the Evinrude 4-60 racing motor built prior and during WWII from Chicago, Don Nichols and Bruce Nicholson who probably started the trend with the Yamaha cylinders in the late 70;s/early 80's, and Michael Schmidt from New England with Kawasaki cylinders also in the 1980 and possibly before time frame. Jack Kugler and his son Jeff from Hamilton, Illinois took over the last models of the Quincy engines built for racing, although using Yamaha crankshafts with cylinders of their own design, instead of basing the motors on Mercury crankshafts as O.F. Christner did when starting Quincy Welding in the 50's. I am sure I have missed some, but not for any reason other than my memory is not as good as it once was.

Add to that the fact that the most famous of the PRO motors after WWII to the present have been designed, built, and in the case of the Konig and GRM motors, even campaigned/raced successfully to start and later on also by the builders, and the PRO category is probably one of the few places anymore in motor sports of any kind that the small backyard builder can compete on a level playing field with a larger factory operation.

There is and has been much of this type of innovation in the PRO Category for many, many years now, and is just one of the things I have loved and appreciated about it and the reason I competed there for the entirety of my racing career.

[David_L6]

Good run down there Bill. Thanks for another history lesson. I (and I'm sure others here do also) appreciate it.

When I think of those kind of motors I think of Quincy (naturally) and Mike Schmidt. If there were any others more successful than those two, I don't know who they were.

[fbref5269]

great rundown

that was a blast from the past with all those pro engine makers. i am lucky enough to have one of kay harrison's 250 engine and several quincy z engines( 125cc, 175cc and rb) in my collection. it is amazing to see what quincy did with a block of aluminum. all this before the cnc machines!

frank
52-E

[Mike Schmidt]

12:15 lower unit

I have a real nice Yamato unit here that I built for a customer years ago that has never been run. New gears, shafts, bearings and seals. The only used parts in it are the case and the screws.

Give me a call at 860-349-9310 or E mail me at teammsr@comcast.net

Mike Schmidt