too much pitch?

[truax42]

i am running an 89 stratos fs279 with a 120 evinrude. just replaced the prop with a 14 x 21 3 blade. boat had a 13 3/4 x 21 3 blade when i bought it. i tried to get the exact same size but after an hour arguing with the salesman ( he was convinced i did not have a 13 3/4 x 21 on an 89 120) i bought the prop anyway , the old one spun and i needed one pronto. <br /><br /> it seems it takes forever to get upon plane, i have to actually move people or gear to the front to get it up on the water i am running with an average load of gear and passengers.<br /><br /> i cant tell you what the rpms were with the other prop. i just bought the boat this spring and it took this long to get the bugs worked out of it. after getting eveything replaced or repaired (boat sat dry for 8 yrs) i finally got it up on plane and discovered the spun hub<br /><br /> after i get up on plane it goes great up to 4700 rpm's then has a slight miss in it. not sure whats causing this. sppedometer dont work so i dont know my top speed but am certain i should be getting more rpm's. any tips here??<br /><br />many thanks!!!

 

[Hooty]

Re: too much pitch?

With that "slight miss", we can't tell if you're over-proped or not. If the engine was running 100%, you had trouble getting up and then the engine only spun 4700 rpm, I say you were over-proped but like it is, you can't be sure. I'd get the engine cookin' first, then start on the prop.<br /><br />c/6<br />Hooty

 

[LubeDude]

Re: too much pitch?

I believe Hooty is right, How about letting us know what all you have done to the engine. Im sure it will be long, (or should be), and we will see if we can get ya cookin first. If thats all shes got, then you might even have to go clear down to a 17P to get the Rs back up.<br /><br />Man it ticks me off when people will not listen and sell you something else because probably thats what he had in stock.

 

[walleyehed]

Re: too much pitch?

If this is an OMC prop, SS or Aluminum, it's either 12-3/4", 13-7/8" or 14". That's all that is/was available in 21" pitch.<br />The 12-3/4X21 pulls about 300 more RPM than the 14X21, but has about the same speed.<br />Just some prop low-down.....Hope ya get your engine up to par, then we can fine-tune'r.

 

[truax42]

Re: too much pitch?

after carb rebuilds, i had a new water pump installed and i replaced the vro with a standard replacement pump (vro too expensive) mechanic done a compression check. all four around 150. spark test was good. new fuel lines from the tanks to the carbs were installed and the tanks were cleaned the best i could. damn things were too big to remove from the boat. never seen anything like it!! <br /><br />new plugs were installed then i hit the water, thats when i learned the hub was spun. <br />walleye you were right. it was a 12 3/4 not a 13 3/4. my mistake. <br />i wish i could tell more to help fine tune the problem but thats all i can think of right now. feel free to ask anything and i'll let you know

 

[Dhadley]

Re: too much pitch?

If you replaced the fuel pump with a "standard" one (single) and mean like the ones on a V4 crossflow, that may be the cause of your "miss".<br /><br />Or do you mean the one that looks like a fuel/oil pump but has no oil side?

 

[truax42]

Re: too much pitch?

one that looks identical to the fuel/oil but no oil side

 

[Dhadley]

Re: too much pitch?

Good pump. That should be OK.

 

[truax42]

Re: too much pitch?

maybe this will help explain the miss a little better. all rmp's up to 4700 are smooth and great, when it hits 4700 it acts as if i hit a rev limiter or something, back it down to 42-4300 and it is fine. is it possible the timing may need reset at wot?

 

[Dhadley]

Re: too much pitch?

I dont think the timing itself would do that. It can be off a bunch in either direction and still be smooth until it sticks a piston.<br /><br />I have seen a power pack do that or a coil. I would test it under a load on the trailer and watch the ignition with a timing light. If you mark each cylinder on the flywheel you can watch each one. The ignition may be going into a double firing situation.

 

[truax42]

Re: too much pitch?

what are the max rpm's i should be getting with this setup?

 

[Dhadley]

Re: too much pitch?

The rev limiter is either at 6200 or 6700 depending on which pack you have.

 

[truax42]

Re: too much pitch?

looks like i am a long way from that. you advised to testit under load. can you explain how i do what you suggested?

 

[Dhadley]

Re: too much pitch?

We do it by leaving the boat secured to the trailer and backing down the ramp until the water pump is covered completely. You may have to adjust the trailer position forward or back. <br /><br />Start the motor and after its warmed up you can have someone put it in gear and SLOWLY increase rpms. While your throttleman is doing that you can check each cylinder with a timing light. If one is missing you will hear it and see it on the light.