When I purchased the new engine I moved the old prop to the new motor. It was a 15 1/4 X 19 three blade. It was obviously too much prop and given that the lower unit ratio is higher geared than the old one I wasn't surprised. It would only turn it about 5200 rpm/WOT. I bought a 15 1/4 X 17 three blade and the rpm at WOT only came up to about 5400. Approx. same load. The engine just didn't seem like it was going all out.
I was looking over the engine a few days ago about a different issue and decided to take a look at the throttle linkage and make sure the throttle plate was going full throttle. I have the mechanical model called XB. I thought the "mechanical" designation meant that it was like the old 3.3L in that it was a mechanical linkage all the way to the throttle plate but that is not the case. It is only mechanical to the end of the cable from the binnacle, where it is connected to the actuating arm of a potentiometer. From there it is "fly by wire" to a slave potentiometer which positions the throttle plate. To test whether it was going full throttle, I turned on the master switch.....turned the key to the "ON" position....pushed in the shifter disconnect and advanced the throttle lever on the binnacle to "FULL". When I looked down the throat of the intake I could see that the butterfly lacked quite a lot reaching the proper full throttle setting. That being, the plate aligning perfectly parallel with the air stream in the throat of the intake. There is additional travel available on the potentiometer arm where the control cable is attached so I manually advanced that arm to full stop while watching the butterfly. No change. If any of you guys are up on the workings of this system I would sure like to hear your thoughts on why that throttle butterfly isn't opening completely. I do wonder if the computer won't open it fully unless it senses the engine is running. I haven't had a chance to observe it at full throttle on the water. Here is a picture looking straight down the throat. I know if this was your drag car you wouldn't take it to the strip like this. Ideas??
I was looking over the engine a few days ago about a different issue and decided to take a look at the throttle linkage and make sure the throttle plate was going full throttle. I have the mechanical model called XB. I thought the "mechanical" designation meant that it was like the old 3.3L in that it was a mechanical linkage all the way to the throttle plate but that is not the case. It is only mechanical to the end of the cable from the binnacle, where it is connected to the actuating arm of a potentiometer. From there it is "fly by wire" to a slave potentiometer which positions the throttle plate. To test whether it was going full throttle, I turned on the master switch.....turned the key to the "ON" position....pushed in the shifter disconnect and advanced the throttle lever on the binnacle to "FULL". When I looked down the throat of the intake I could see that the butterfly lacked quite a lot reaching the proper full throttle setting. That being, the plate aligning perfectly parallel with the air stream in the throat of the intake. There is additional travel available on the potentiometer arm where the control cable is attached so I manually advanced that arm to full stop while watching the butterfly. No change. If any of you guys are up on the workings of this system I would sure like to hear your thoughts on why that throttle butterfly isn't opening completely. I do wonder if the computer won't open it fully unless it senses the engine is running. I haven't had a chance to observe it at full throttle on the water. Here is a picture looking straight down the throat. I know if this was your drag car you wouldn't take it to the strip like this. Ideas??