Got 2005 150vmax hpdi yamaha, round 700 hours...compression is a little low and top end dropped avg 58 to 52...anybody got experience with those indicators???

How low? Have all the fuel filters been replaced lately, including the screen in the vst?

First thing to check is throttle linkage going to full throttle. Second thing to do is change the manual fuel pump diaphrams. You can get a higher % of ethanol and cause a reduction in power.

thanks guys for the advice....

Have you verified the low compression? Normally it will start with one cylinder and you notice a rough idle or will not idle at all. With that kind of MPH drop and barring other factors I would think you are low across all and not making full power. If you are lucky it is just some carbon build up and sticking rings. If you have not done the de-carbon treatment then try it.

Stump jumper is on to something you should try too. Put Ring Free in the fuel. Have seen that make a lot of difference on Yamahas.

had it checked, (105,107,110,110,110,113)yamaha guy said it's not bad for 150...guess i will try changing gas and adding ringfree.

Compression sounds fine to me for a high hour motor. Have all the fuel filters been replaced in the last year?

Don't just add ring free to gas. Get a can of powertune and follow instructions on can. I use Quicksilver.