not running WOT

[dennis352]

I purchased my boat not running and just recently repaired it. I have no history to compare it to so this could be entirely in my head but it seems incorrect. At WOT my 90 GT 150 is only running 4300 rpm. I have a 14.5 x 20 raker prop. The boat is a 90 javelin 19' f&S and from everything i ve read the motor should turn this combo about 5500. Im getting 52 mph on my gps but my rpms dont match. I have a installed a new pack and stator. Any ideas? My tach works seems to work fine. Could this be carb related? Thanks

 

[JB]

Re: not running WOT

Could be your tach calibration, Dennis, or you could be a bit overpropped.<br /><br />I doubt that a sick engine would get you to 52mph with that boat.<br /><br />I would verify the tach calibration first, then look at the prop.<br /><br />Good luck.

 

[rickdb1boat]

Re: not running WOT

I think JB is on this one. Are the pole settings "6" on the back of the Tach? 20" prop sounds a little high for your rig. You may want to drop down to a 17" and see how it does. Also, if you are friendly with your dealer, he may let you borrow a shop Tach to verify your readings possibly with a small deposit. That would be the first thing to do, before messing with the prop...

 

[Dhadley]

Re: not running WOT

Assuming your GPS is correct, I would agree that the tach is somewhat off. <br /><br />The 20 Raker should be just about right for that hull. If we use a 10% slip factor, you would have to be turning right at 5800 to get 52 mph.<br /><br />Still assuming your GPS is correct, your motor would have to be running correctly to get that speed and true rpm.<br /><br />However if your GPS is remembering what your truck speed was on the way to the ramp.......<br /><br />Seriously, I would look at the tach, as mentioned, to verify a setting of 6. What brand tach is it anyway?