Thanks for all your help with my repower video of the high speed runs

[krisnowicki]

I went out this morning and did a wot run to get some number now that I am at about 16 hours.
I swapped the 454 omc king cobra to a 350 alpha merc magnum and so far I have a wot around 4900-5100 depending on conditions with a 19inch prop and a speed of 54 ish. So I think I will move up in pitch to a 21 and try get it in the 4600 area per manual #15. Spec is 4200-4600 this is a non roller cam

Is it better to run the top or low end of the recommended spec?
Also check out the steam. it was a cold Florida morning ( low to mid 50's)

heres the video and thanks to every one for helping.

http://www.youtube.com/watch?v=kEqh-oN1e6M

 

[dragtuners]

Re: Thanks for all your help with my repower video of the high speed runs

really nice video

 

[Don S]

Re: Thanks for all your help with my repower video of the high speed runs

It's best to be proped to the top end of the range with a NORMAL load on the boat.
Then with more load, you will still be ok, and real light (probably unlikely on most boats) you just have to pay attention when going WOT.

 

[krisnowicki]

Re: Thanks for all your help with my repower video of the high speed runs

dons does that steam look typical to you?

 

[Don S]

Re: Thanks for all your help with my repower video of the high speed runs

dons does that steam look typical to you?

Engine under high load and rpm = very hot exhaust gasses. Passed through water when it's 50 some degrees outside and humid ??? Sounds normal to me.

 

[CheapboatKev]

Re: Thanks for all your help with my repower video of the high speed runs

Engine under high load and rpm = very hot exhaust gasses. Passed through water when it's 50 some degrees outside and humid ??? Sounds normal to me.

boat contrails!

 

[HT32BSX115]

Re: Thanks for all your help with my repower video of the high speed runs

Hey! Nice job.....great video! It didn't appear that exceeded about 4800 or so.



Sounds good too! I'll second the top rpm suggestion. You want to be at the upper range when at WOT loaded where you will run it most of the.

Make sure that your tach is accurate and you're using GPS for before you do any "propping"


I think it unlikely that you'll hurt the engine by going a little high on the RPM....and the 21 may be a little tall for it.....You might consider getting the 19 cupped/pitched to 20. It's a SS prop?


I would take 4700/4800 over 4500 as the top RPM.

 

[krisnowicki]

Re: Thanks for all your help with my repower video of the high speed runs

the cupped 20 is what I am think or maybe a four blade. I know spec is 42-4600 but I would like to keep it 46ish maybe 47. It did get to 5100 ( the rooster tail was huge at that point)and I am gettin 15% slip so I figured the tach is right or really close. I didn't tape it at 5100 because my wife was taping then. It was 8 in the morning we had spent the night on the water. Ans she was cold so we went in after this run. But, I am happy with the results I am going to get my buddy's 21 and try it this next weekend. Also, I will keep my 19 for heavy lads and wakeboarding.

thanks again guys

 

[krisnowicki]

Re: Thanks for all your help with my repower video of the high speed runs

and yes I am only using stainless props.

 

[HT32BSX115]

Re: Thanks for all your help with my repower video of the high speed runs

the rooster tail was huge at that point

Is this "on purpose"?

If not, you may be trimming the drive too far out (up) that'll kill top end .... Also, I have found that I can improve my holeshot by trimming all the way IN (down) and right as it planes, I trim it out until it runs the best speed....It's very sensitive and has a pretty small range of settings that works...

A 4 blade (20p) might be the best balance between 19 and 21. It may cause a tad more (prop) drag at top speed but will improve your hole shot a little ...

Absolutely try the 21 if you have someone that will loan it to you. Do another video too.....that was pretty cool!


Cheers,


Rick

 

[krisnowicki]

Re: Thanks for all your help with my repower video of the high speed runs

my standard op is to trim all the way down. Wait till I get close to plan the start bringing it up until both sholders are out of the water I have the lest amount of drag. The rooster happened but the prop never slipped or cav'ed and my speed and rpms kept rising . I only had it there for about 30 seconds. you can see some of it in the video, it never got bigger than what you see in the video. I have never had a boat that would launch water in the air without cavitating first. I will take it out on friday and do it all over.