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38kv performance questions
I just picked up a 85 38kv it has twin EFI500’s and TRS drives, I took it to a local lake and ran it around to see what I need to do for props. She ran 55mph on gps and wouldn’t push past 4,300rpm at 5,300ft elevation 3 people on the boat and 3/4 of a tank. I have Bravo1 4 blade 26p props on it now, so I figured I needed to drop to a 22p. Over memorial weekend I went to a different lake at 6,100ft elevation same props 3/4 tank but 10 people on the boat this time and exact same numbers and no noticeable difference in plane time or power... I’m not great with how much props change the performance overall other than changing rmp‘s but this seems like it’s maybe some other issue holding the boat back. Any advice?
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never had a 38 scarab but i would think 26 are too big props... i had a 357 formula twin 485 dyno hp and 23 was the biggest prop i could swing max wot. so your hull is not lighter than my 357 was, similar hp, same TRS...
i would start 21 and go up if needed |
i would think a stepped 38 could swing those 26, or 25
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I probably need to go to a 22 it just doesn’t make sense to me that with an extra 1700lbs worth of people it didn’t change anything. It jumps on plane fast and doesn’t seem to power out just hits a wall. Just looking for more experienced opinions before I drop 2k on props
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I had an 82 KV - the notched transom model - running 23 p three blades at 5000 rpm it would just crack 60 mph. That was the best performance I could get out of the boat; that was with 450 hp a side. I found the boat liked the older three blade Mirage better than a Bravo 1.
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I would run a 3 blade Mirage instead of the 4 blades because your TRS drives are mounted very low and it will be hard to make a 4 blade work properly. Regards Dan
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Thank you Team Archer!
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i am running 4 blade quad 4 hydro motives, 26 pitch,
was mentioned to me , i should be running a bravo prop, but .. running 82mph, 5600 rpm, 10% prop shipage ,"" hard to argue with."" i talked to bbblades and that was there comment. straight vee bottom here |
That's because the Hydromotive props have smaller blade area than a bravo prop. They try to lift the back of the boat to much with a low X
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How much HP does it take to make a 38KV run 82?
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I would guess... 700's? To 800's?
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What were they running back in the day with the kaama boat? I seem to remember reading they were in the 80’s but I don’t think I ever heard what they were pushing power wise. There would be a substantial weight difference but would be cool to know. I saw there is a Kevlar 377 with the twin turbo 454’s for sale on Ohio right now🤤
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Wait just looked again it’s in Oklahoma
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My 377 ran 70 mph with amybe 500 HP/side with TRS drives and spinning 24" bravo 1's I know Randy Otts' 38 KV would run 70 with the same props with 500 EFI and Bravo drives.
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I have a good pair of 23 pitch mirage plus with removable hubs, i will sell you for 350 dollars plus shipping if your interested.
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Outonsafari sent you a pm
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https://cimg5.ibsrv.net/gimg/www.off...9e5f2183e0.jpg
https://cimg9.ibsrv.net/gimg/www.off...dcf7ce61dd.jpg https://cimg2.ibsrv.net/gimg/www.off...73c4ecf413.jpg https://cimg7.ibsrv.net/gimg/www.off...f494537a48.jpg https://cimg4.ibsrv.net/gimg/www.off...f261496499.jpg https://cimg1.ibsrv.net/gimg/www.off...b199c7c431.jpg https://cimg5.ibsrv.net/gimg/www.off...2d6780a85f.jpg as mentioned in the text let me know and i will box them up on monday. at that time i'll make sure customer service counter is open at ups. Once shipped i will text a picture of the shipping label the shipping costs and trackings numbers, and you can paypal me the shipping cost. paypal has to be friends and family so there isn't a charge. thank you |
Done deal, txt me your info and I’ll get some money headed your way
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Ok thank you, call/text ya monday
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Originally Posted by Team Archer
(Post 4741143)
That's because the Hydromotive props have smaller blade area than a bravo prop. They try to lift the back of the boat to much with a low X
so ,,you think i would still run better with bravo style prop???? i talked to bblades,,,said 10% slippage is pretty good. just curious thanks |
Your slip number is good I am just saying that the lower X dimentions don't work as well with 4 and 5 blade props.
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Got the new props on, ended up going with a lab set of bravo1 3 blade 21p. I’ll post up the numbers once I get it on the water. Since my last post my trailer had a major come apart so I’ve been replacing brakes, bearings, all 6 leaf packs, a spindle and the hitch. Needless to say my last trip home from the lake was an adventure. I’ll put up some pictures as soon as offshore allows me to
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the real question that needs to be answered is how did you get 10 people into the cockpit of a KV??????
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Hahaha lots of booze😂 and the cuddy
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Should be done rebuilding the trailer this week and have an update with the new props. I have been seeing posts that the KV tends to do a little better on the top end with the props turning in (mine currently turn out) has anybody tried it and checked the numbers? While we're on the subject how do you turn TRS drives the other direction, is it just flipping the linkage on the trans? That was my original assumption but I see there is a left and right hand drive
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No you have to swap drives they are right and left hand rotation. Regards Dan
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Thanks Archer Is there any real gains to turning in?
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Ok finally got the trailer wrapped up and hit the water. Now running a 21p 3 blade bravo prop and got 56.6mph at 4,500ish rpm... almost no change from the 24p 4 blades... I was blowing out the left prop easily
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Your rpms are very low for 21p props; 470 hp with three blades should easily rev to 5000 rpm. The RPMs should definitely vary depending on number of blades and the pitch of the blades, whereas it seems they are staying constant for you. I'm pretty sure the mercury 330 motors normally rev to 4600 with the 21p three blade mirages.
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I want to turn the props in on my TRS drives, I've read that you need to swap the drives side to side, or you can just swap the lowers. Does anyone have any input in which is easiest?
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The easiest way to switch rotation is to switch the whole drive. Disconnect your tie bar, remove the trim rams at the outboard end. loosen the trim rams on the transom assembly. and then remove the 6 bolts holding the drive to the helmet. make sure you have new gaskets for the drives. beforehand. I use gaskets off ebay like $6 each.
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Originally Posted by phughes69
(Post 4778861)
The easiest way to switch rotation is to switch the whole drive. Disconnect your tie bar, remove the trim rams at the outboard end. loosen the trim rams on the transom assembly. and then remove the 6 bolts holding the drive to the helmet. make sure you have new gaskets for the drives. beforehand. I use gaskets off ebay like $6 each.
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I can finally post pics so that is the boat. I'll post as I do stuff but it is more of a long term project. This years plan is to blueprint the bottom, get rid of the graphics and fix a glass issues in the cuddy, I think I am going to gut the front and ditch every bit of wood in favor of composite. The long term plan is to have a wood free boat hopefully shedding 1k lbs or so, quad turbo the 500's since it was an option back in the day, drop the floor a few inches so you sit further in the boat and do the betty cook 89 kaama paint job. I am far from being a knowledgeable boat guy I have had a few but my background is in building hot rods and fabrication so any input along the way will be greatly appreciated!
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Boat looks nice! I also pondered going composite when I started into mine. My reasoning was that the boat is never going to be fast by modern standards, so I opted to put it together with plywood and do a better job sealing it.
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If it runs an honest 75mph I’ll be more than happy, I’m more doing it for efficiency towing, cruising around and to never have to worry about rot again. I’ve replaced wood on every boat I’ve ever had and it sucks. This era of boat just looks fast and bad ass just cruising lol. Btw hb this project is about 78.5% your fault! I’ve always drooled over the flat decks and your build was the nail in the coffin
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Sorry. 😁 When I was considering buying my boat I called up glassdave to try to get him to talk me out of it. He said something like “I’m the last guy to call for that”. So we all kinda spread this unhealthy addiction around.
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Drug the boat out to my big shop so I can use the overhead cranes over Easter to yank the motors and reseal them. My plan is to sandblast and paint the gimbles drives and trannys while everything is apart. I plan on painting the transom black as well. Pulled all the hydraulic cylinders and had them rebuilt (lift cylinders were leaking like crazy) and hopefully have it back together by Monday night. My question is do I use the rear water intakes or the bottom pick up? The rears have been plugged off since I got the boat.
https://cimg1.ibsrv.net/gimg/www.off...76c67c153.jpeg https://cimg3.ibsrv.net/gimg/www.off...51788917e.jpeg https://cimg5.ibsrv.net/gimg/www.off...fad47af4e.jpeg https://cimg6.ibsrv.net/gimg/www.off...e9cee20cd.jpeg |
From what we have found the transom mounted pickups work better at the higher speeds. If you need some I make the ones that Heath is using on his project. Regards Dan
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Decided to stick with the water pickups in the bottom of the boat for now, the rear pickups are in pretty poor shape. My old lady stopped by yesterday and peeled the wrap off so I’m down to a blank canvas now. The transom and rear stringers are solid so that is a huge relief 😅
https://cimg7.ibsrv.net/gimg/www.off...8d37082dd.jpeg https://cimg0.ibsrv.net/gimg/www.off...d0c594712.jpeg https://cimg7.ibsrv.net/gimg/www.off...e854657b7.jpeg https://cimg8.ibsrv.net/gimg/www.off...bbeda079b.jpeg |
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