VP 5.7 Gxi hits rev limiter @ 4300

[doh13]

HI my buddy has a VP 5.7 Gxi in a 24 ft Grady white offshore 24 dual SS prop (not sure of pitch yet as she's in the water ). We noticed it wont hit the rated rpm of 5000-5200 when cruising and when revving the motor in neutral she seems to be bouncing on a rev limiter at 4200-4300 rpm (if the gauge is accurate) he gets a top speed of approx. 43-45 mph @ 4300 rpm , we changed the plugs out with fresh NGK TR55IX plugs (are these correct?) and a distributor cap/rotor The old plugs looked rich and sooty . Do you think the ecu has a lower rev limiter rpm set or could there be another issue?

 

[alldodge]

(if the gauge is accurate

Start by checking the boat Tach. Get a hand held Tach or scanner to compare

 

[BRICH1260]

Make sure your throttle plate is opening to 100%. Might need a throttle cable adjustment.

 

[doh13]

Make sure your throttle plate is opening to 100%. Might need a throttle cable adjustment.

throttle plate opens fully

 

[doh13]

Start by checking the boat Tach. Get a hand held Tach or scanner to compare thanks was thinking of that

Will have to check into that thanks.

 

[QBhoy]

Hi. Out with the likely explanation being the tacho being off the mark…it could be that you have one of many faults that can cause a 90% power guardian mode. But normally there is an alarm for such a thing I’d think.

 

[doh13]

Hi. Out with the likely explanation being the tacho being off the mark…it could be that you have one of many faults that can cause a 90% power guardian mode. But normally there is an alarm for such a thing I’d think.

There was no alarms it revs to approx 4200 in netural then hits a rev limiter and the same under load in gear , your right that it could be many things , I tested the fuel pump pressure and it was holding at 50 psi at high rpm . I need to get a rpm tester to see if the gauge is off , If it's not that then he will have to get a tech with the vp software to see if there's any error codes etc.

 

[QBhoy]

There was no alarms it revs to approx 4200 in netural then hits a rev limiter and the same under load in gear , your right that it could be many things , I tested the fuel pump pressure and it was holding at 50 psi at high rpm . I need to get a rpm tester to see if the gauge is off , If it's not that then he will have to get a tech with the vp software to see if there's any error codes etc.

Ok. Strange one. So is it seeming as if it’s actually hitting an electronically governed limiter and cutting ignition at those rpms ? Could be that the tacho is just off the mark and it’s actually more like early 5000’s in reality. You can get a thing called Volvo Penta easy connect or something like that. It can send exact info on data, rpms, P&t’s etc etc from the ecu. Reads out on your phone, tablet or some compatible chart plotters. That would tell you exactly what’s going on.

 

[doh13]

Ok. Strange one. So is it seeming as if it’s actually hitting an electronically governed limiter and cutting ignition at those rpms ? Could be that the tacho is just off the mark and it’s actually more like early 5000’s in reality.

Yea seems like it's hitting a rev limiter for sure, the tachometer seems to be the likely culprit . I will have to verify with an rpm reader or look into the vp adapter when I get the chance thanks for the info.