225 (03) honda with jet pump at altitude

[salmonstriper]

I have a 2003 honda 225 with a jet pump and at the high altitude lakes the boat will not always reach over 4k rpms. This is a fuel injected model and every so often when I am plowing water going from one fishing spot to the other at 3800 rpms w.o.t it will all of a sudden get a little burst of rpms and seem to clean itself out or breath or something and jump up about 1000 rpms and get on plane and run like a champ. I cant get it to do this all of the time and it is very frustrating. At sea level the boat has no problems at all and will hit 6k rpms at any time. I have recently put a new water fuel seperator, attempted to drain the vst?? (the clear tube on the back of the motor that requires the little screw to be backed out a few turns) when I did this only a little fluid would come about 5" out of the tube and just stay. I tried a few more turns and that did not make a difference. Any other advice? Thanks Brad

 

[chawk_man]

Your VST drain port is clogged, which is an indicator that you probably have some junk in there.Try opening and closing several times. If that doesn't work, close it tightly, and with the screwdriver still in the slot, tap the top of the screwdriver several times with a small hammer, and try again. If that fails, turn on the key to activate the HP fuel pump. The little bit of extra pressure, may loosen the blockage.

If that fails, it's time to remove the VST and tank, and clean them thoroughly. While your in there, remove the HP filter and inspect or replace. However, that is not likely your problem since your engine is running fine at sea level.

3800 rpm's is not WOT, so you do have a problem. The ECM in the 225 is supposed to adjust for changes in barometric pressure. It is possible that the sensor has failed, or you have a loose wire. Check the wires from the ECM to the barometric sensor. It is a 3-prong connector. The barometric sensor is located on the front of the engine, straight across from the oil filter and directly below the oil filler tube.

If you know how to pull MIL codes using the service connector, the MIL will blink a "13" - one long blink and three short blinks. That indicates a bad wire to the sensor, or that the sensor has failed.

 

[bvs]

I'm 99.999% you DON'T have any problems with any VST port draining issue, bad sensor, fuel problem, or any other problem with your motor. Your only problem is altitude. You are lacking air pressure and oxygen.

Every 1000ft above sea level you loose 3% of your horsepower. At 5000ft your motor is a 190hp motor. At 9000ft it's only 164hp. Fuel injection will keep you from running too rich at high altitude, loosing even more hp, and fouling your plugs but that's it. The ONLY way to avoid the HP loss is supercharge or turbocharge your engine, which isn't going to happen on your motor.

However, you can compensate for it by "gearing down", but with a jet pump than if you had a prop.

I also have a Honda 225 on my boat. I own a 19" pitch prop, a 17" prop, and a 15" prop. I use the 19 at sea level up to 1000ft, the 17" for 1000-3000ft, and the 15" from 3000ft up.

If I forget and leave the 19" prop on my boat at 5000ft, I can't get my RPM's over 3000, nor will the boat ever get up on plane. I gear down with the 15" and I can almost hit the rev limiter up to 6000ft and can still barely hit 5000rpm at 8000ft. However, my 50mph boat is only a 42mph boat at 4000ft and a 38mph boat at 8000ft.

I don't know about jets, but the only way you are going to get decent performance at altitude is to either gear down or change your impeller pump. The good news is that you will save gas. By boat burns 20gph at WOT at sea level but only burns about 15gph at 8000ft.

Things are even a bit worse with a jet pump because they are less efficient to begin with. Maybe you could swap the lower end out with a prop for the high-altitude lakes and then go back to the pump for running the rivers. Good luck.