Jacking a 640

[Mike Nelson]

Hi there.



I have a 2005 640lx with 90HP Opti running a 20p laser 2. Currently the engine sits on the 2nd highest hole and I can run 43mph at 5750rpm. The trim never seems to be ideal so I am considering a manual jackplate to get the engine sitting correctly. I am after some suggestions.



1. What amount of setback would suit best?

2. Would I loose holes hot or gain?

3. Would a jackplate be ok on the transom? Boat is in very good condition.

4. Is anyone running my setup currently?



Thanks guys, any suggestions would be much appreciated.



AUSNITRO

 

[fatrap]

Been there done that didn't help at all. With a 170 Ricky Clunn

fatrap

 

[byron cooley]

Something is very wrong with your set-up. My 04'640LX 05'75 Optimax is all over the limiter of 5850 with a 20" Laser II. My motor is also mounted 1 hole from the highest. I have more than enough bow lift as it will run up on the pad with 0 spray from the sides of the boat. Mine will run 46.3gps@the 5850 limiter with a balistic holeshot. With my 22" laser II it will run 50.6gps@5800 by myself with a decent holeshot. I don't know your elevation but I run at only about 400ft above sea level. Oh yeah - it's been tweaked to a 90.

 

[Gilbert Scales2]

AusNitro, I have a Nitro 640 with a 6" manual jackplate .. and a a 2002 90HP Mercury. It has a Laser 2.. 22 pitch prop. I have my motor up above the transom, about 2 inches. No cavation in the turns, good hole shot. WOT rpm's are 5600. Top speed with nothing in the boat except me, and a little gas.. is 45.6 mph... GPS. Most days it will only get 44.3 MPH. If I were you I would not spend the money. I tried everything to get my boat to 50 mph. Fatrap results were the same as mine, none of this helped me. If it did anything it was lower the balance in my checkbook.



Bubby

 

[Mike Nelson]

Hi Byron, my boat does have a sweet holeshot with half fuel and two people and well emtpy. Mine is also all over the limiter with the 20p laser 2. Sweet so i will have to look at getting a 22p laser 2 then. Do you guys reakon it would be worth getting a jack plate even if it does not produce any more speed. Will it give me better holeshot and stop its lower speed porpoising. ?

 

[fatrap]

Aus

I spent amost $400 on a HiJacker six inch and I tried it everyway possible even going to the dealer and having them twink it. I had a 90 Evinrude so maybe some difference there. The only benifit I had was there was a small amount less water over the transom when coming down off plane quickly.

I happened by a prop expert while in Missouri at one of the big resivoirs there. He told me that you needed at least a 150 hp or so to gain a about 6km/h from a jackplate. All in all between the ss prop and jackplate and a couple suggestion from Bass and Walleye Boat magazine I spent about $1000 and gained nothing in speed. I finally settled with a 19 pitch SS that was on it when I sold the boat.

My best ever with that setup was on a chilly day slight ripple cold water. I hit a wopping 77 km/h the same speed it ran on the first day I ran it brand new with the stock set up. That was with just me a light load little gas and empty livewell.

Good luck on your quest for speed keep us informed. PS I had a 170 DC Ricky Clunn. The best thing about it was the jackplate looked really cool:cool

fatrap

 

[Mike Nelson]

Thanks for the info. I am not really look in specifically just at the speed however in the near future my engine will be tuned to PRO XS 115 specs so I am guessing I will see a bit of speed gain then considering the PROXS 115 is prob about 120 or so HP. Reasons for wanting jack place.

1. Will look sweet.

2. Will allow me to trim the motor a bit nicer.

3. Will hopefully throw a bit of a rooster tail for showing off (currently can

 

[byron cooley]

Plate looks cool and you wan't a rooster tail. Maybe you should have bought a jet drive ski boat.:lol:

 

[Bill McElroy]

Aussie,...high Rooster tails may look cool...but they're a dead giveaway that you're trimmed too high and losing a LOT of speed.

 

[Mike Nelson]

Yeah guys i am aware of that thanks, to be serious though do you guys think i will gain the above improvements i mean its only gunna cost me about $400 to give it a go, i cant make my boat worse can i?

 

[byron cooley]

Hey Aussie - Check your Email.