03 225 honda with jet pump still only 4k rpm

Ok well I thought that the high altitude was the cause for my poor performance with my 225 honda jet outboard. I recently ran it back as sea level and the motor was not really crisp and snappy like it used to be and will only go up to about 4100 rpms. Motor seems to run fine and just has no umph for top end. I ran a load with 4 guys plus myself today and was a battle to get it up on plane. I stopped by a jet pump shop on my way home just to see if it was the pump but after a resharpening of the impeller and tighter spacing for the impeller it still would only obtain 4k rpms with just me in the boat and the jet pump at the right tollerences. Water fuel seperator has been done within the last 10 hours of run time. Boat is a 22.5 welded jet sled.

There could be a lot of causes. But the first thing I would look at are the throttle connections and cables.

First, with engine off, take off the cover, put in gear (gently), push throttle full open and inspect whether the throttle lever arm (at the cable cam wheel) is up against the stopper. It should be. If not, before adjusting, pull throttle back to idle speed, put shifter in neutral, and follow the cables to the throttle cam wheel (on top of the engine toward the rear) and make sure they are not damaged or kinked.

At the throttle cam wheel, make sure the adjustment nuts are tight. Measure the distance between the adjustment bracket and the end of the cable adjustment threads. The should be 9 mm on both. If not, adjust.

Back to the throttle cam where the lever is located - measure the length from the end of the threaded part back to the adjustment nut - the open side (to your left as you are facing it) should be 14 mm. The close side (to your right) should be 19mm. If not, adjust.

Put back in gear, and push throttle all the way forward. Throttle arm on the cable cam should be up against the stopper. If not, then you likely have a problem with the cable from your throttle control to your engine, which will need to be adjusted or replaced.

If the throttle arm is up against the stopper, then look at there the roller sits in the throttle cam. It looks like a fat inverted "L". The roller should be almost touching the top of the narrow part of the "L". Then pull the throttle lever at your control all the way back, and put the engine in neutral. The roller should now line up with the "V" mark on the foot of the "L." If not, adjust the linkages until the roller does what it is supposed to do - touch the stopper at full throttle and line up with the "V" mark at minimum throttle.

Hope this makes sense.

I pulled the plugs to check them out and the second one down on the port side was not even tight. Could this be part of the problem? I will clean all of the plugs and put them back (189 hrs on them) or should I just put some new ones? Thanks

Yep - that can sure cause your problem if you were loosing compression on that cylinder. The plugs are supposedly good for at least 400 hours. If the plugs are NKG's, and they look clean, continue to use them. If they are not NKG's, replace them with NKG's - IZFR6F-11. Carefully clean the loose plug with alcohol or acetone. When you replace each one, coat the threads with a light coat of anti-seize grease. That will keep them from seizing to the head the next time they are pulled.

salmonstriper said:

I pulled the plugs to check them out and the second one down on the port side was not even tight. Could this be part of the problem? I will clean all of the plugs and put them back (189 hrs on them) or should I just put some new ones? Thanks

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Test for spark, or just replace all the plugs...I would do the latter. Any brownish tinge at all...

I lost 2 plugs boat could only manage 3300 rpm with one person in it..

Also check if the throttle plate is wide open when in operation....

This can screw up the fuel supply system as well....

And "confuse " the computer.

Put six new plugs and I am out to the lake now to test it. The people that I had look at the plugs said that they did not look well and one was shot.

Back from the run on the high altitude lake and boat ran great and had no problem hitting the 52-5500 rpm range. I found some plugs that are much cheaper than the ngk plugs. Check into these if you are looking to save some dough. autolite xp xtreme performance xp5224. They were about 6.50 apiece. Let me know if they are ok for the honda application. On the outside of my honda motor it gives a couple of spark plug references and then also say or equivelent so I gave these a shot for the money.