Merhama 225 Four Stroke

[boscoe99]

Fairdeal, have you noticed that Mercury specifies a maximum voltage test and a current test for the subject motor? Same as your 3.3 liter F225 of course.

[99yam40]

just exactly what voltage and current are you writing about.
into or out of the RR maybe?

and what would cause too much voltage?

[fairdeal]

Fairdeal, have you noticed that Mercury specifies a maximum voltage test and a current test for the subject motor? Same as your 3.3 liter F225 of course.

you mean this?







much of it puzzles me;
#3 and #4,
and also I don't see why the 'ammeter test' would be showing full alternator output...

[boscoe99]

just exactly what voltage and current are you writing about.
into or out of the RR maybe?

and what would cause too much voltage?

I am addressing the output voltage from the R/R as well as the maximum available current from the electrical generation system.

The Yamaha SM only provides a minimum voltage (13) for the R/R. No mention is made of the R/R having to much voltage. The Mercury manual lists 14.0 ~ 15.0 volts as being excessive.

The Yamaha SM makes no mention about available current from the generation system. Whereas the Mercury SM does.

It was interesting to me (and maybe fairdeal since he has a 3.3 liter F225) that the Mercury manual provides more (better?) data about the Yamaha made motor than does the Yamaha manual.

Kind of a side issue but you may have read where many people complain about Yamaha R/R's having what they consider to be too much voltage. They change the R/R and the new one does the same. But since Yamaha does not provide a maximum output voltage there is no way to say that the voltage is truly excessive.

[boscoe99]

you mean this?






much of it puzzles me;
#3 and #4,
and also I don't see why the 'ammeter test' would be showing full alternator output...

Yes, that is the data I saw.

#3 makes sense in that a bad battery could result is the voltage being below the output specification. So they are saying that if the output voltage is too low, to fully charge the battery to see if the minimum voltage will become acceptable. In other words, don't be fooled into thinking the R/R is bad when it might be a battery issue. Could have been stated better IMO.

#4 seems to be just another test of the battery to see whether it is bad or not. If it fails a load test (which is what they seem to be doing, using the starter motor as the load) then to replace the battery before coming to the conclusion that the R/R is defective.

As noted in my tests, and based on what I have read, the R/R shunts most of the electrical power within itself. Such that it cannot normally be seen with an ammeter. But if the red output lead and the black ground leads of the R/R are shorted together, with an ammeter being in the circuit, then the full DC output capability of the system can be seen.

When I get my test rig back together I will perform this test on the Yam R/R that I have to see what can be seen.

[boscoe99]

voltage and amps depend on each other for actual power delivered. 500 amps with 12v is not the same as 500 amp at 5v. Ohms law.

Absolutely electrical power is dependent upon voltage and amperes. Which is why it is so very strange IMO that there is nary a check of amperes in any Yamaha SM that I have ever seen. I was quite surprised to see it in a Mercury Manual actually.

[99yam40]

I am addressing the output voltage from the R/R as well as the maximum available current from the electrical generation system.

The Yamaha SM only provides a minimum voltage (13) for the R/R. No mention is made of the R/R having to much voltage. The Mercury manual lists 14.0 ~ 15.0 volts as being excessive.

The Yamaha SM makes no mention about available current from the generation system. Whereas the Mercury SM does.

It was interesting to me (and maybe fairdeal since he has a 3.3 liter F225) that the Mercury manual provides more (better?) data about the Yamaha made motor than does the Yamaha manual.

Kind of a side issue but you may have read where many people complain about Yamaha R/R's having what they consider to be too much voltage. They change the R/R and the new one does the same. But since Yamaha does not provide a maximum output voltage there is no way to say that the voltage is truly excessive.

Strange that you say Merc says to replace RR if v too high, but then you state on some Yamahas replacing the RR did not help when Voltage was too high.
What did they find other than the RR caused the high voltage?

[boscoe99]

Strange that you say Merc says to replace RR if v too high, but then you state on some Yamahas replacing the RR did not help when Voltage was too high.
What did they find other than the RR caused the high voltage?

Only the R/R can cause the high voltage. The issue between Mercury and Yamaha is what is too high and what is not too high.

If the R/R output voltage is higher than X, Mercury says to replace the R/R. Voltage is too high.

If the R/R output voltage is above 13 volts Yamaha says life is fine. Apparently any voltage above 13 volts is not too high in the eyes of Yamaha.