I am currently looking at a boat with 2004 Mercury 225 Four-Strokes with less than 100 hours on them ..

I know nothing about blenders and would like to learn more about these engines..

I have heard they were built by Yamaha for Mercury...

Pros and Cons?

How many hours are they good for?

If you had a choice between these and Optimax'swhich would you pick? (Gas and go application..... Not Go-Fast)

Thanks

Frank

Opti's are lighter and less complicated. Word on the street is they do a bit better on gas than the 4 -strokes. Don't know if this is true or not, but I've heard this from people who've had both.

4 strokes are heavier, and a lot of the times quieter, especially at lower speeds.

I'd pick Opti's

It is true the Merc 4-strokes were builty by Yamaha?

Hmmm .... I am a little surprised you have never heard that.
Look here:
http://www.rbbi.com/links/outboard.htm#makes
It says:
2006 model Mercury four strokes from 2.5 through 30 HP are built by Tohatsu.
Before Yamaha entered the U.S. market, Mercury's Mariner line was built by Yamaha.

Last year (2005), Mercury four stroke powerheads from 25 through 225 HP (except the Verados) were built by Yamaha. Several of those models used Mercury drive legs, electronics and EFI systems (replacing carbs Yamaha used in similar sized engines).

In 2006 models, Mercury four stroke powerheads from 40 to 225 HP (except the Verados) are built by Yamaha.

Mercury's agreement with Yamaha ended in March 2006, at which time Mercury is expected to phase in more four cylinders (75 to 115 HP) based on the Verado engine block, but without supercharging or intercooling.

As for the reason I don't know. But may be because even though Mercury is a large company, my guess is that their research and development resources are limited. May be Mercury was busy working on the Verado line and needed large 4 strokes before the Verado line was ready. But I am only guessing.

the engines that were in fact built by yamaha and mercury was a joint venture. yamaha needed mercurys lost foam casting techonogly and mercury needed yamahas quality control.

What is lost foam casting?

Wow! now that was a quick response MarylandMark, thank you!

I think the General invented lost foam, OMC used it first ..( as far as I know) in the marine world on 3cyl V4 V6 V8 loopers in the 80's.
The reason for it is you can cast internal pipes and the foam goes to gas so it can escape the molds very easily.
In the old days the sand or your die had to get out and this limited what you could cast.

Its just a new version of lost wax...like the Egyptians used