1995 mercruiser 454 inboard rpm goes up and down

[German lopez]

hi i have sea ray 330 sundancer 1995 with 454 inboard on it one of the engine after 40 min running when im at 4000 rpm goes down to 3500 rpm then up to 4000 rpm then down again i replace the rotor the cap the oil oil filter fuel/water separator i tried using the other side fuel tank and keep doing the same . can someone help me please thanks in advance

 

[hottoddie]

Please confirm that you were running your 454 at 4000 rpm for 40 minutes. If so do you do that on a regular basis?

 

[German lopez]

No i usually run it at 3200 to 3500 rpm but after 40 min to an hr even at 3500 rpm the engine goes down to like 3000 rpm then up again to 3500 so i move up to 4000 to try but was the same it goes up and down and today after 30 min runing didnt want to pass 3000 rpm

 

[rwvw415]

I’m having the same issue on my 1987 454 Pachanga I keep the engine speed the same and the tach moves form 3000 to 4500 then settles back down for a while and starts it all over again. It must be electrical but I have not figured it out as of yet.

 

[German lopez]

I’m having the same issue on my 1987 454 Pachanga I keep the engine speed the same and the tach moves form 3000 to 4500 then settles back down for a while and starts it all over again. It must be electrical but I have not figured it out as of yet.

Ok thank