OK I just got my props back from being lab finished and got no increase in rpm's or speed. I don't know where to turn next. The boat is a 1999 eliminator daytona cat twin HP500's carb. Bravo1 30 pitch 4 blades turning in. I tried them turning out and were a little slower. The boat runs to 94 mph on gps and turning 5000 rpms. This is exactly what it ran with the props brand new out of the box. I called eliminator boats and they told me they use John York from York propeller for all of their race boats and said he is the best. I called him & he felt he could get 200 more rpms easily maybe get 300. Well after the labing I got the exact same results. Other guys on this site with same rig claim 97+ at 5300 rpms. The former owner claims that the boat ran 100 at 5350 rpms? The boat has 300 hours on the motors and the are both spinning the same rpms so it leads me to think that one is not down on power and I would find it hard to believe they both would equally be down on power due to some sort of failure.Could it be timing? The boat was purchased in California and the fuel out there is different I think? I am running on a lake in NJ at 900 feet above sea level. Could this be the reason. The people I bought the boat from never ran it in slat water so I know that is not reason. I am going to run it at the jersey shore aug 14th for a week and I will see if see level makes that big of a difference. I am so frustrated and don't know were to look. Any help would be appreciated. Especially from the eliminator dyatona owners.

Have you had the motors scanned for codes? I know it is not likely that both would have a problem at the same time, but who knows.

I have not had that done. The engines are not efi's they are carbs and I think the computer does very little on these motors.

You are right, it was just a thought. Sorry.

At 300 hours I would think the valve springs could be getting tired. They can be a great rev limiter. Do you know if they have ever been changed?

I do not think they have ever been changed. Is this a big job changing the valve springs? Do the heads have the come off? If so I will live with it until I need to rebuild the motors. I just find it odd that previous owners only put about 50 hours on the boat and they were getting more revs and mph. Do valve springs slowly weaken? I know they were prone to breaking on these motors but they were checked out by Teague custom marine and were not broken.

Not that I think that it's urgent, but valve springs and lifters are regular maintanence items in an engine like yours. After the mess I had when a roller lifter broke in one of my engines, I will never neglect them again. Over the winter I would get a valve job and replace lifters and valve springs.

200 or 300 rpms... I've seen that much difference between a nice mild day and a hot humid day. 900 feet altitude will make a difference too. Where did the last guy get his 100 mph? That too will make a difference

Your valve spring DEFINATELY need changed. Do a search on Valve Springs and HP500 here on OSO. This has been discussed about 1200 times.

The last owners ran the boat in lake havasu and lakes around Los Angeles. I do not know the altitude out there. When I flew out to California to see the boat the lake the owner took me to seemed like it was up in the mountains but I do not know the altitude. Does it seem odd to get no difference in any thing like RPMS or Speed from labing props. I would of thought something would change. The boat feels as if nothing was done. Also do you guys think Hydromotive 4 blade labed 29 pitch would run better the the bravo 4 blades? Any suggestion's are greatly appreciated.