Question for Joe / 225 Johnson Venom

[bobecke]

I've got a 97 225 Venom on a 96 Bullet (1200 lbs.) 4B 27" renegade prop at 2" below pad with 12" setback. Engine has fresh powerhead and runs great but won't get more than 5200-5400 RPM's. This rig in the past would easily turn 5900-6000 RPM's. Any suggestions of things to check?? Thanks in advance!!

[Joe Reeves]

Bob... I retired years before that engine came into existence, however what you're saying is that the engine has lost roughly 500 rpm. That would be (again roughly) the rpm loss if one cylinder ceased to function.Start troubleshooting with the basics ie compression (Approx 100 psi, even on all cyls), spark on all cylinders that will jump a 7/16" gap. S/plugs must be out for the spark test.

[Dhadley]

"New powerhead" -- did this new powerhead ever turn the r's? Or has it always been down on rpm?

[bobecke]

Thanks guys. Yes Dhadley, the powerhead did turn more RPM's but I rarely pushed it as the powerhead was/is still fairly new. When I was running double oil (VRO and 50:1), I became suspicious that the VRO stopped working as the oil didn't seem to go down in the res. as it should have (no alarm) so I unhooked it and premixed. It was since then that I noticed that it couldn't get much past 5,000 RPM. Could there be a connection?? Also.. if I'm losing a cylinder at high RPM, wouldn't I be able to hear it as the motor would be running less smoothly??Thanks. Bob

[Joe Reeves]

Bob.... Yes, the loss of one cylinder would no doubt be noticed at a low rpm, however should the engine be firing that cylinder at a low rpm but not at the higher rpms.... that might get by you.In doing away with the VRO setup, I assume that you are still using the VRO pump, but using it strictly as a fuel pump. Did you plug the oil line on the VRO? If not, that would allow it to draw air and would obviously create a problem.(VRO Changeover Judgement Call) (J. Reeves) The VROs first came out in 1984 and have been upgraded quite a few times. In my opinion, back around 1988, they had perfected them but I think that they were upgraded even more since then. As long as the warning system is operating as it should, I feel quite at ease with them.Some boaters have voiced their thoughts such as "What if that overpriced plastic horn should fail while I'm under way for some reason, and the VRO decides to fail five minutes later?" Obviously that would result in a big problem which really brings their fears into view.The word "ease" is the key word though. If one has the slightest feeling of being ill at ease with that setup, then they should take the route they feel more at ease with. A judgement call each individual would need to make on their own.********************(VRO Pump Conversion To Straight Fuel Pump)(J. Reeves)You can convert the VRO pump into a straight fuel pump, eliminating the oil tank and VRO pump warning system, but retain the overheat warning setup by doing the following:1 - Cut and plug the oil line at the engine so that the oil side of the VRO pump will not draw air into its system. Trace the wires from the back of the VRO to its rubber plug (electrical plug) and disconnect it.2 - Trace the two wires from the oil tank to the engine, disconnect those two wires, then remove them and the oil tank.3 - Mix the 50/1 oil in the proper amount with whatever quanity fuel you have. Disconnect the fuel line at the engine. Pump the fuel primer bulb until fuel exits that hose with the tint of whatever oil you used. Reconnect the fuel hose.That's it. If you want to test the heat warning system to ease your mind, have the key in the on position, then ground out the tan heat sensor wire that you'll find protruding from the cylinder head. The warning horn should sound off.Another thought..... If all of the above is okay. And if I can assume you're using Champion QL77JC4 spark plugs, and you have them gaped at .030, try gaping them at .040 .