Yamaha pump question

NWRedside · 09-07-2005, 11:15 AM

Just posted this on the boat doc thread but wanted some other input as well....

I just purchased a 2000 150 yamaha vmax a few weeks ago and had a jet and tiller put on it. I've only put about two hours on it since everything was rigged. Should I be concerned that I'm only getting 5100 RMP out of it at full throttle? I checked all the obvious things I could think of like making sure I'm trimmed correctly, getting full throttle with the linkage in the tiller arm, and making sure my bucket is all the way in the down position. I've been told that these motors should run at 5500-6000 rmp WOT. What other things should I check or should I be concerned about potentially something wrong with my new to me engine?
Engine is mounted on a 20' open woolridge sled.
thanks!
Nathan

reelfine · 09-07-2005, 12:46 PM

One possibility may be that the motor has a stainless steel impeller. An SS impeller is a little heavier than a standard aluminum and you may lose some upper RPM's (although this does not mean you are losing speed/lift).

When I installed a SS impeller in my F115 Yamaha (granted, a 4-cyl instead of a V6, but maybe still applies), I lost about 300 RPM, but on-step, top-end, and load carrying at lower RPM's were all improved.

NWRedside · 09-07-2005, 12:54 PM

thanks for the reply. It does have a four bladed stainless in it. I hadn't thougt about that being an option for the loss of RPM's. I have no compliants from a speed perspective as I'm sure I'm mid to upper forties at WOT.

Boat Doc' · 09-07-2005, 01:06 PM

Max rpm is 5-6000, if you want it to be higher they do offer a cut back impeller that will increase the rpm, however cruise speed/rpm will change - less speed at same rpm.

Fish Fever · 09-08-2005, 03:25 PM

Nathan,

I wouldn't worry about it. My last 2 yamaha's were just over 5000 turned wide open. 200 Vmax with a stainless impeller was 5100 WOT. New 225 four stroke with pump or prop on only gives me about 5300. What I've found is I only run it there for a few seconds here and there as needed to get on step or around a hazard or of course when we are going to a hot bite. Otherwise we gallop along in the 4000's and save fuel.

Sounds like a nice setup.

Dave