2003 25hp 4 stroke yamaha F25ELHB

[rageingcajun67]

I bought this motor used it had been overheated and sitting up for a while. Head gasket was blown, resurfaced head and replaced gasket, replaced water pump assy, flushed all the sand from lower unit and cylinder head that caused overheat to start with. Cleaned carb engine cranks and idles great, cooling system does well will idle all day but will only rev to about 1500 rpm, it acts like its in some kind of limp mode. It has 135lbs compression on each cylinder and is firing on both cylinders was wondering if there is a test for the CDI module or a wiring schematic that I can get to be sure its getting all the right inputs for the CDI module. Or can the module be reset or flashed to bring it back on line. Any help would be appreciated thanks

[rodbolt17]

about the only other test than inputs and outputs is does the ign timing advance with RPM.

[rageingcajun67]

25 hp yamaha

No the timing will not advance with increased throttle

[rodbolt17]

if pulser coil and charge coil inputs are good, most likely the CDI died.
the ign advance is electronically con*****ed by the CDI based on pulser coil inputs.

no timing advance and the engine starts breaking up about 1500-2000 RPM.

[rageingcajun67]

Yamaha F25ELHB

Thanks for the info since it will run all day at idle so I'm gona assume the pulser coil is fine or it would'nt idle or crank as good as it does guess I'm gona order a CDI thanks again

[99yam40]

pick up a Yamaha service manual for your motor and follow the steps for testing ignition system.
Do not just guess some things are in spec , test them.
Or take it to someone that can test

Did you read what Rod wrote?
He put an if in that post

if pulser coil and charge coil inputs are good, most likely the CDI died.
the ign advance is electronically con*****ed by the CDI based on pulser coil inputs.

[rageingcajun67]

25hp 4 stroke

checked pulser coil and running at idle its about 17.5 Volts and raises with idle to 32 volts until its starts bogging because its not advancing the timming

[99yam40]

what did you measure with?
Sounds way high for a pulsar coil voltage

[rageingcajun67]

2003 yamaha 25hp 4 stroke

fluke 78 back probed at the pluser coil it ohmed at 311

[rageingcajun67]

25hp yamaha 4 stroke

I checked it running at idle and as fast as it would rev, I set the meter on ac and hit the peak button to check pickup coils, don't know what the spec is so don't know if its to high or to low

[99yam40]

get a Yamaha service manual for your motor to get the specs and procedures and use the correct meter or a DVA adapter with your meter to read the DC voltage like the manual calls for

[rodbolt17]

a fluke 78 without a DVA adapter wont correctly read DC voltage peak.
it does an average voltage.

you should see a minimum peak voltage of 6V cranking and a minimum peak of about 18V at 1500.
minimum of about 35V at 3500.

my guess if its not advancing the CDI is faulty.
it is a merc motorala ign system.