MAX RPM'S ON A 1992 5.OL OMC/COBRA OUT DRIVE

[Chuck Rowe]

I have a 1992 190 Horizon by FourWinns. It has the 5.0l OMC with a Cobra King out drive and I am running a AL prop that is 14 1/2 X 21. It will not turn more than 3900 RPMS. Is that normal for the type of motor/out drive and prop that I have. Is there a way to turn more RPM's to go faster than it's top speed of 37 MPH.<br /><br />Thank You <br />Chuck

 

[motox6]

Re: MAX RPM'S ON A 1992 5.OL OMC/COBRA OUT DRIVE

my 93 horizon peaks at 46-4700

 

[motox6]

Re: MAX RPM'S ON A 1992 5.OL OMC/COBRA OUT DRIVE

Chuck my 93 190 horizon was doing 45MPH with a cracked block 15X19 prop. You should be doing better than 39MPH. Also check tune-up (cap, rotor, plugs)because when I first got that boat it too would only run 35-39MPH and when I tuned it up even with cracked block she was doing 43-45MPH

 

[Cobra SX]

Re: MAX RPM'S ON A 1992 5.OL OMC/COBRA OUT DRIVE

LOSE THAT 21 pitch!!!!<br /><br />You are running a 5.0 is it carb or Injected ?<br />you have a little more power on a injected.....<br /><br />Now OMC cobras are good drives , they have coffee spilling Hole shots on a 17 pitch , the have the best performace of both hole/top end on a 19 pitch<br />and crappy hole shots and more crusing above plane with a 21 pitch.....<br /><br />NOW check this out you boat is made to run at about 4200-4600 WOT rpm you are OFF(running lower)by between 600-800 rpm. That is alot my friend.<br /><br />You may ask.... why is that bad?<br /><br />Well to answer that, you are kind of okay....<br /><br />BUT listen to this, WOT throttle is design'd to give the boat the MOST HP(ponys) through out the entire RPM as well as at the TOP. Not only that but very harmful carbon build-up starts to slowly take place, when the engine is not able to meet its WOT. This will lead to "lug" on the engine,higher running temps, and detinaiton.<br />Which harm engine performace....<br /><br />So you could say your boat isnt running to its<br />-" full "-<br /><br />I would Go to a 19 for best cobra performace ALL around. (hole/load/top)<br /><br />But you can spend some $$$ and deck out the engine<br />(I would) I tell you your boat will love you for it But at this point your 21 is lug'n that boat...<br /><br />think if it was full of peeps , tow'n somthing<br />it has to struggle to get up to plane right?<br /><br />By the way are you alum or stain prop ?

 

[butchsmoke]

Re: MAX RPM'S ON A 1992 5.OL OMC/COBRA OUT DRIVE

When you say lose the 14 1/2 x 21 pitch isn't that the 4 Winns spec on this boat? I had that prop on mine and ran fine but not sure what top RPM was ... maybe 4900. The prop is pretty beat up and there was a much better one in the boat but it does not look nearly as used. So I put it on and the boat was
pulling 5400 rpm or better. I did not let it wind right out for fear of a problem (you know used boats). This prop is a Michigan prop but the number does not seem to come up anywhere. You are saying optimum rpm is 4700 or 4800? I seemed to be getting that on the factory spec prop - think it is a Michigan Vortex aluminum.