2800 sx twin ob setup results

[2tonchevy]

hey people...just wanted to share the results after running the boat this weekend since there seems to be alot of conjecture and not much solid info/results on the propper setup of this hull. hope this helps

1987 2800sx ob

im running twin 225 promax 2.5 mercs. 20 inch mids, sportmaster 1.87 counter lowers. 26p 3 blade merc chopper props. latham hydro steering. at neutral trim the nose cones are 30 inches fro the transom.

they prop shaft center lines were dead even witht hte bottom of the boat (in front of each engine respectively) when i purchased the boat.

i raised the prop shaft center lines to 1.5 inches above the hull bottom. major improvement. top speed. acceleration. and handling were all notably improved. the low water pickups on the sportmasters are now dead even with hull in front of each motor respectively. porpoising was also reduced.

the change also drastically reduced the amount of positive trim required to achieve top speed.

overall it was just what this boat needed. i actually could use some 28p choppers now because i can hit 6300 rpm easily on top.

anybody wanna trade some 28 choppers for some 26 choppers??? lol

 

[RNGRDVE]

You forgot to mention what speeds you are seeing.

 

[2tonchevy]

lol yeah idk what he top speed is...but it hauls ass...ive had it in the 70s for sure without even pushing it all the way .... its noticeably faster (better all around) than when i bought the boat both by feel and by the conventional water pickup speedo.

i havnt gpsd the boat nor have i maxed the boat out all the way. i need some 28p choppers....i can hit the rev limiter with ease now....

 

[SCT]

2ton,
I was running more setback then you but with the sportmasters and 28' choppers, I was running a real high x dimension. I never did measure it but kept on raising the j/ps until I did not like the handling. Like you said, the handling improved the higher I went. The only part I did not like with the choppers was the high nose rise when coming on plane and the props breaking lose if not careful.

I still think you should try a set of Bravos with vent holes. They were my best all around prop and only a few mph slower then the choppers but a LOT more user friendly. The Bravos did like a lower X then the choppers, though. The speedo shot was with the Bravos.

I just got rid of a nice set of offshore cut 26 choppers that would have been perfect for you-

Good luck-

 

[2tonchevy]

2ton,
I was running more setback then you but with the sportmasters and 28' choppers, I was running a real high x dimension. I never did measure it but kept on raising the j/ps until I did not like the handling. Like you said, the handling improved the higher I went. The only part I did not like with the choppers was the high nose rise when coming on plane and the props breaking lose if not careful.

I still think you should try a set of Bravos with vent holes. They were my best all around prop and only a few mph slower then the choppers but a LOT more user friendly. The Bravos did like a lower X then the choppers, though. The speedo shot was with the Bravos.

I just got rid of a nice set of offshore cut 26 choppers that would have been perfect for you-

Good luck-

hey thanks for the reply!

i have a set of 26 bravos sittin in my shop to try next time out. they dont have the vent holes yet...but they should still work the same once on plane right? if i like em ima have the prop shop here drill em for me. i dont mind the planing and handling of the choppers......but then again i havnt tried anyhting else either. the choppers seem to give a "seat of the pants" type of feel when runing fast. but i have no comparison so that may be just the way the boat is.

what year was that boat?? thats a bad dude for sure.

 

[SCT]

It was an 06 bost. I agree the choppers are fast but a very "loose" feeling on the top end. I guarantee you will like the Bravos. Did you ever determine if your boat is the old Ocean Outboard race boat?

Good luck-

 

[2tonchevy]

It was an 06 bost. I agree the choppers are fast but a very "loose" feeling on the top end. I guarantee you will like the Bravos. Did you ever determine if your boat is the old Ocean Outboard race boat?

Good luck-

i will def be tryin the bravos i have. they are also 26 p but the extra blade should bring my rpms down.

my boat is no the ocean outboard boat..but acccording to lightspeed..a member that built/rigged it...it is a direct copy of the ocean outboard race boat. the only difference being the stainless marine floatation setback bracket instead of gil tubular brackets.

im very pleased with the improvements so far...i still feel that there is a few more tweaks that can help the overall package....

very fun boat and withthe addition of the cuddy couches and the rear swim pad over the splashwell its a pleasure to take tha ladies out for a spin on.

 

[illMATTic]

Did you ever get any photos of the cabin? How did it turn out?

 

[xsive]

hey people...just wanted to share the results after running the boat this weekend since there seems to be alot of conjecture and not much solid info/results on the propper setup of this hull. hope this helps

1987 2800sx ob

im running twin 225 promax 2.5 mercs. 20 inch mids, sportmaster 1.87 counter lowers. 26p 3 blade merc chopper props. latham hydro steering. at neutral trim the nose cones are 30 inches fro the transom.

they prop shaft center lines were dead even witht hte bottom of the boat (in front of each engine respectively) when i purchased the boat.

i raised the prop shaft center lines to 1.5 inches above the hull bottom. major improvement. top speed. acceleration. and handling were all notably improved. the low water pickups on the sportmasters are now dead even with hull in front of each motor respectively. porpoising was also reduced.

the change also drastically reduced the amount of positive trim required to achieve top speed.

overall it was just what this boat needed. i actually could use some 28p choppers now because i can hit 6300 rpm easily on top.anybody wanna trade some 28 choppers for some 26 choppers??? lol

I'm curious as to why you think you need new props? Promax 225's have a factrory 6750 Rev limiter and at 6300 RPM you are just getting into the sweet spot for those motors.

 

[2tonchevy]

I'm curious as to why you think you need new props? Promax 225's have a factrory 6750 Rev limiter and at 6300 RPM you are just getting into the sweet spot for those motors.

well hell... lol

i was told that they redline at 63-6400...

if they redline at 6750 ,.......and its safe to run themabove 6500 for extended periods (couple minutes at a time)...then i feel that i should just leave it alone.

do you agree??

the boat handles great...accelerates hard...planes out fast....and responds quickly now that the prop shafts are up a lil more...(1.5 inches above the bottom) theres really nothing else i would change at this point.

but it still hits the 6300-6400 mark very quickly....even with a nearly full tank of fuel.

i was just thinkin of tryin to get a better cruise speed....but after talkin to several people more learned than i....i think my bravo 26s are gnna be what i want for that....

 

[2tonchevy]

Did you ever get any photos of the cabin? How did it turn out?

hey!

cabin and rear deck turned out great! makes the lines of the boat flow very nicely and gives plenty of seating options.

the boat looks like a pleasure boat now instead of a race hull.

the couches in the cuddy are comfortable and can seat 3 on each side. havnt put in a berth yet and dont know if i will...i dont sleep on my boat.but we'll see. also the 85 ft of red LED rope light i hid in the cockpit and cuddy light it up very nicely...

ive got some pics but havnt figured out how to post em...any body wanna help??

 

[xsive]

well hell... lol

i was told that they redline at 63-6400...

if they redline at 6750 ,.......and its safe to run themabove 6500 for extended periods (couple minutes at a time)...then i feel that i should just leave it alone.

do you agree??

the boat handles great...accelerates hard...planes out fast....and responds quickly now that the prop shafts are up a lil more...(1.5 inches above the bottom) theres really nothing else i would change at this point.

but it still hits the 6300-6400 mark very quickly....even with a nearly full tank of fuel.

i was just thinkin of tryin to get a better cruise speed....but after talkin to several people more learned than i....i think my bravo 26s are gnna be what i want for that....

No worries on running them close to and tickling the limiter on occasion. If you prop them for 6500 RPM max under normal conditions that is about perfect.

 

[2tonchevy]

just wanted to update:

im switching to drilled mid sections with the exhaust liners removed and 28 merc 3 blade choppers this week. may raise the engines up another notch after testing if all goes well. as long as my water pressure is above 10 lbs im good right??

any idea how much my rpm should drop at WOT switching from 26p choppers to 28p choppers??

i still havent tested my bravos either....waitin to get my boat back together.

interior is totally redone and the hatch in the front has been installed. its comin along....

 

[JUPITER PULSARE]

just wanted to update:

im switching to drilled mid sections with the exhaust liners removed and 28 merc 3 blade choppers this week. may raise the engines up another notch after testing if all goes well. as long as my water pressure is above 10 lbs im good right??

any idea how much my rpm should drop at WOT switching from 26p choppers to 28p choppers??

i still havent tested my bravos either....waitin to get my boat back together.

interior is totally redone and the hatch in the front has been installed. its comin along....

Chevy, did you pick up Hemi's 28 Choppers?? I still haven't decided on props yet..I'm thinking 26's as the 28's are probably too much prop for stock 200's...

 

[2tonchevy]

hey man! nah i bought a set from a guy on oso.

and depending on your gearset..they may be too high.

 

[JUPITER PULSARE]

hey man! nah i bought a set from a guy on oso.

and depending on your gearset..they may be too high.

We should be fairly close in setup. From what I understand the Promax puts out more power upstairs while the 2.4 200 has more torque downstairs (I tend to question that logic but that's what I've been told). I'll probably settle on some 26 Choppers to start. I now have both my motors mounted. I haven't measured my centerlines yet but the boat was setup for racing..there is only about an inch of clearance between my motor cowls!!! Hopefully I'll get some more work done next wednesday..

 

[2tonchevy]

yea i dont know about any of the HP or torque ratings either. i know mine came out of the hole like a monster with 26s and would hit 6500 rpm in the blink of an eye. and that was before drilling my mids and modding my exhaust tuners as per Jay smiths recommendations. it should spin the 28s just fine when i get it back together this week.... i think but we'll see.

what is the distance between steering pins on your engines?? i read somewhere that 22.5 inches was the closest you can mount twins???

and with our set up being very similar i would put your propshafts about 1.5 inches above the bottom and try that. it made a huuuge difference in mine. keep in mind tho that your boat will be heavier by nature in the bow to a certain extent due to the added interior pieces and structure.......and this can cause the balance to be different...so you may not be able or required to run your engines as high as i have mine cus when the bow rides lower the stern rides higher..... im 90% sure i could raise mine up another hole (.750 INCH) and still be just fine. but instead i think i will try to add some weight in the nose first and see how that effects the flight of the boat.

my boat shines at wide open throttle. (just like LIGHTSPEED said it would) the faster you go the better it handles and flies. low speeds the nose gets a lil lighter. but still a great handling boat....and gettin better all the time!

PS: my new interior , hatch, carpet and controls look awesome! waaaay better than before. engines are off and totally disassembled. all the parts are in...new drilled mids are painted and the liners are removed. all new motor mounts , studs, gaskets and hardware are going back on this week. planning on bein in the water by friday!

i will get some pics asap!

 

[JUPITER PULSARE]

yea i dont know about any of the HP or torque ratings either. i know mine came out of the hole like a monster with 26s and would hit 6500 rpm in the blink of an eye. and that was before drilling my mids and modding my exhaust tuners as per Jay smiths recommendations. it should spin the 28s just fine when i get it back together this week.... i think but we'll see.

what is the distance between steering pins on your engines?? i read somewhere that 22.5 inches was the closest you can mount twins???

and with our set up being very similar i would put your propshafts about 1.5 inches above the bottom and try that. it made a huuuge difference in mine. keep in mind tho that your boat will be heavier by nature in the bow to a certain extent due to the added interior pieces and structure.......and this can cause the balance to be different...so you may not be able or required to run your engines as high as i have mine cus when the bow rides lower the stern rides higher..... im 90% sure i could raise mine up another hole (.750 INCH) and still be just fine. but instead i think i will try to add some weight in the nose first and see how that effects the flight of the boat.

my boat shines at wide open throttle. (just like LIGHTSPEED said it would) the faster you go the better it handles and flies. low speeds the nose gets a lil lighter. but still a great handling boat....and gettin better all the time!

PS: my new interior , hatch, carpet and controls look awesome! waaaay better than before. engines are off and totally disassembled. all the parts are in...new drilled mids are painted and the liners are removed. all new motor mounts , studs, gaskets and hardware are going back on this week. planning on bein in the water by friday!

i will get some pics asap!

Sounds great! Can't wait to see all the pictures! My mids are 25" one piece mids with the cans removed and I'm using one piece hi-performance exhaust adapters between the mid & powerhead. I have my motors mounted at the highest setting on the Gil Brackets. I'll have to measure the propshaft height this wednesday..the Gil Brackets have natural lift built into the bracket. My boat is very light..the boat was layed up with AME 4000 resin and the cabinets have been removed from the boat. The only structure in the cabin is the ply that forms the V-birth in the bow..I'll be working on my boat his wednesday! Can't wait!!

 

[2tonchevy]

yes id say with your cabin stripped...your boat is every bit aslight as mine (or lighter, i dont know if mine was layed up with the light resin or not)

cant wait for ya to get that thing on the water! its VERY hard to find solid info and results for setup and performance on this hull. bee cool to have some fellow owners to bounce ideas and results off of!

your makin good progress tho for sure! keep it up!