twin 03 250 evinrudes

[jserb]

Re: twin 03 250 evinrudes

DH im thinkin about running a 21 pitch, do you think itd be a bit to much knowing how your buddies boat preformed? Also, your comments about the trim tabs have not been forgotten, however i thought i would put the boat in the water and test run it, while having my buddy look over the transom and watch to see if at any time my water pick up comes out of the water, do you think if i have him watch it, while i do a few test runs and if the water flows between the AV plate and the water pick up, i will be ok? anything in particular i should have him look out for?

let me start by saying: I AM SORRY!!! I know how redundant this thread is for you, you just have to realize this is 8 months in the making and i dont wanna miss anything, i look at your profile and it seems like your the wizard when it comes to this so i am trying to get the most thorough answer from you. With that said; you previously said my lower units look "O.K." relative to the bottom of the hull, do you mean like "ehh they just look ok" or "they look fine, no worries"? Have you ever seen this where the hull falls right in the middle of your water pickups on your lower unit? I AM SORRY!!!

 

[Dhadley]

Re: twin 03 250 evinrudes

No need to be sorry, I know how these big projects go. I'm not concerned about the hull being in the middle of the pick ups at all. Even if it was an issue we could plug the top holes, or even the top 2 holes. I am concerned about the tabs.

 

[jserb]

Re: twin 03 250 evinrudes

DH- Just a quick question reguarding my Trim Tabs, i am going to cut them down tonight and it occurde to me that your words were "nothing should be 12'' from the lower unit". Now bow to stern the tabs are a good 14'' from the LL. Now port to Starb they clear them by an inch, i was planning on takin gthe 12X20'' tab down to 12X12'' tab= Thus giving me 7 inches port to starb from both LL to the tabs. Is is ok?

 

[jserb]

Re: twin 03 250 evinrudes

DH- i need your responce for before tomorrow!!

 

[hwsiii]

Re: twin 03 250 evinrudes

Jserb, if you haven't already cut the trim tabs I would hold off on doing that, I would put your props back on the boat and try some speed tests and see where you are at now. Do you have water pressure gauges on the boat to tell you if you have enough water pressure for the engines? If so send me your email address and I will send you some forms to fill out for boat weight and speed tests so we can see where you are now.

H

 

[jserb]

Re: twin 03 250 evinrudes

Ok here we go: I had the boat weighed and it was 7080lbs with the trailer, now it is a steel tri-axial trailer so I estimate it weighs 1200 lbs: which in return I just replaced with the weight of fuel : about 1000 lbs, we had 3 guys and one lady totaling 700 lbs, so if you all this all together you get a total weight of 8000LBS fully loaded when I ran her for the first time. Now we reached a top speed of 46 knots= 53MPH. The boat handled well, however the starboard motor wanted to jump up wayyyy high in RPM as we got on plane and im not sure why. The motors were in unison while at idle, and then at 2000 RPM and at 3000 just as we were getting on plane its like the port motor got a bunch of gas and wanted to take off, once on plane I had to back that motor down a bit and raise the starb motor. I THINK it?s a linkage issue, however I did find it wired that when they were below 2500 RPMs they were in unisen, then after getting out of the hole they separated. I am spinning 23 P props and the boat really seemed to get up and go when I trimmed up pretty well. So I guess the bracket is ok? I know when I turn I can see the opposite motor comes out of the water a bit and gains a small amount of RPM?s but nothing to drastic. I would like to get your opinions on how fast im going compared to weight and props and if you would suggest trying a smaller prop? They topped out are 5800 RPM, but I could have gotten them to 6000RMPS no problem if I trimmed out more, does this mean I need large pitch props? It almost seemed as if when I went in and out of gear that those props were so big that they stalled the motors a few times when they were in idle. Anyway that?s the shake down 53mph, 8000LBS, 5800 RPM, = I thought id at least hit 58MPH????? Do you work boyssss

 

[hwsiii]

Re: twin 03 250 evinrudes

Jserb, I ran your new numbers with the new weights you gave and here are the statistics. You have a Prop SLIP of 22% right now and that is NOT good, but if your motors will turn up a litlle more RPM like you said then I don't see a problem. You should be able to turn the right Diameter and Geometry of props at a very respectable RPM. I would like to know exactly what manufacturer and model as well as Diameter and Pitch of the props you are running now, and I am sure Dhadley will too. Dhadley is the expert on the high speed props as far as I am concerned, on manufacturer and models to use.
My opinion is that you either don't have enough Diameter or blade surface area or both. But the correct geometry would take care of this problem as well. With a Slip that high, I think if you increased the Diameter by 1" in the exact prop model you have now, you would lose some real RPM but you would still have a 23" prop turning very respectable RPM, but you would lose a lot of that 22% Slip and I believe possibly get down to around 10% or better and have more speed than you do now. But that is just my thoughts on the matter, listen to what Dhadley recommends.
My numbers show you should be turning a 21" prop with a top speed of between 57 and 60 MPH depending on SLIP.

Prop Slip

For some reason I cannot get the picture function to work, I will try again shortly.

H

 

[jserb]

Re: twin 03 250 evinrudes

H, just some OMC props a guy at the shop let me try. I didnt know you could get larger props for an outboard? I thought they all were the same size? hm i THINK its a 14 1/4? Do you know how much larger a 03 evinrude can go? Thanks H!!

 

[hwsiii]

Re: twin 03 250 evinrudes

No I don't I am sorry, but you know what ask the guys at the shop if they have a pair of 21" stainless props you can try. Preferably with good rake and some cupping if they have it. As long as it is free. LOL
And ask them exactly which props you are using now model number, Diameter and Pitch.

H

 

[hwsiii]

Re: twin 03 250 evinrudes

Jserb, do you have any new numbers.

H