Rpm surge

G

greenhabah

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I have a 1995 Yamaha 225.

First 2 trips of the year seemed to work normal on ride out (2-5 miles) and between drifts, but on ride in (running with the waves 2-3ft) seemed to get a rpm surge of about 300 - 500 rpm's (not the normal surfing down a wave).

Next couple of trips (1ft or less) it seems to happen in the 2500- 3500 rpm range. Seems fine running at 4000 rpm but takes more throttle than normal to get there (if memory is correct after winter). No issues at idle speeds.

The primer bulb is not deflated when it has an issue.

This winter I changed the gas line from the fuel separator to the primer bulb and replaced the primer bulb. Changed the fuel water separator, fuel filter and the plugs.

I'm thinking it is a fuel issue of some sort but open to any suggestions.
 
Is that motor an OX66 or carb?

Did you notice if squeeze bulb collapsed a bit during the exact time it happened?
 
Fuel pumps. 3 of them on the port side of the block. About $42 each to replace. If they've never been done, it's time.
 
BobP said:
Is that motor an OX66 or carb? ?
Click to expand...

Carb

BobP said:
Did you notice if squeeze bulb collapsed a bit during the exact time it happened?
Click to expand...

squeeze bulb was NOT collapsed

gw204 said:
Fuel pumps. 3 of them on the port side of the block. About $42 each to replace. If they've never been done, it's time.
Click to expand...

I have not changed them...I've had it since 2004.
 
I would also get yourself a small 3-gal external tank and run it directly to the motor. That will help you determine if the problem is with the engine or the fuel system.
 
gw204 said:
I would also get yourself a small 3-gal external tank and run it directly to the motor. That will help you determine if the problem is with the engine or the fuel system.
Click to expand...

The results of this test can be misleading. The motor may run fine on the external tank but the low pressure pumps could still be bad. The fact that the fuel level is a lot higher in the boat makes it easier for the motors to pump it.
 
When I've had bad low pressure pumps I've experienced a rough idle also. If I pumped the primer bulb it would run smooth until the fuel was burned.
 
gw204 said:
Fuel pumps. 3 of them on the port side of the block. About $42 each to replace. If they've never been done, it's time.
Click to expand...

On the money.!
 
you obvious have fueling issue

you need to get a pressure and vacuum gauge on there

bad fuel pumps will leave the spark plugs soaking wet, primer bulb can still get hard also

run on an aux tank will tell u if the fuel lines or tank or bulb is bad!
 
Looks like I got a bad primer bulb. I swapped it out for another new one and it has run fine since.


Thanks for the help.
 
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