So just how fast am I going?
Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Boat Maintenance
Forum Discription: Discuss maintenance of your Correct Craft
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=13848
Printed Date: November-17-2024 at 5:14pm
Topic: So just how fast am I going?
Posted By: MdFooter
Subject: So just how fast am I going?
Date Posted: June-01-2009 at 4:51pm
Replies:
Posted By: JoeinNY
Date Posted: June-01-2009 at 5:03pm
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Sounds like she is running pretty good one way or another. With that much weight the OJ might start flexing pretty good at those RPM's and really effect your top speed, or not if you happen to have a boat that naturally runs a bit highter. I think what you should do is bring it up here next weekend and take me wakeboarding, skiing, and maybe hydrofoiling and I will bring along my GPS and we will see what shes really doing. Something seems cruddy about those speedos or tach either way so we do some swapping and get it figured out. My 83's speedos really arent that far off in most situations. ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1477 - 1983 Ski Nautique 2001 1967 Mustang 302 "Decoy" http://www.youtube.com/watch?v=cO5MkcBXBBs - Holeshot Video |
Posted By: GottaSki
Date Posted: June-01-2009 at 5:13pm
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Looks like a nice Mallory dist too.
Well done. ------------- "There is nothing, absolutely nothing, half so much worthwhile as messing around with boats...simply messing." River Rat to Mole |
Posted By: 81nautique
Date Posted: June-01-2009 at 9:26pm
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If your truly turning the 13x13 to 5500 then I'd say you done good but I think something is not right here. A true GPS top speed will tell us if the prop is biting or slipping. Also make sure you check your trans fluid and all is well there. My prop calculator tells me that with an average of 20% slip your boat is running 53.9 mph, Joe knows what it takes to do that so I still think somethings up. The gps will tell.
Those are some great improvements for that boat though , you won't regret it. ------------- You can’t change the wind but you can adjust your sails |
Posted By: Fl Inboards
Date Posted: June-01-2009 at 9:48pm
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Hi. Please do not take this as an insult but more as advise.
I see in your photo a braided line going into the carb fuel inlet fitting and what looks like a hose clamp. If this is so hopefully it is only temporary and you plan on installing a correct fuel supply tube. I see many a older PCM motor where someone thought that the fuel supply inlet tube needed replaced with such as set up as a "cool" braided line and a hose clamp. This set up is a very dangerous situation in a inclosed motor and when they come into my shop this way they get changed at the expense of the owner. Again only observation and advise. Ill get off my soap box now!! ------------- Hobby Boats can be expensive when the hobbyist is limited on their own skill and expertise. 1993 Shamrock "fat" 20. 2008 Nautique 196 5.0 |
Posted By: SN206
Date Posted: June-02-2009 at 1:24am
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Jody,
Could you or someone else please explain why? I am not that mechanically inclined. ------------- ...those who have fallen and those who will. |
Posted By: 05 210
Date Posted: June-02-2009 at 1:27am
It's a fire hazard. It's supposed to be a steel line from the pump to the carb with a threaded fitting. Mike ------------- http:/diaries/details.asp?ID=2219" rel="nofollow - Air Nautique 210 Team 640 hours, not 1 regret |
SN206 wrote:Posted By: 8122pbrainard
Date Posted: June-02-2009 at 10:24am
It's actually a double flare fitting on the ends. 1/4" pre flared brake line and a good tubing bender are needed here!! There are some detailed USCG specs on the high pressure side of the fuel lines. Yes, some hose can be used but it is very specific with specific connections. ------------- /diaries/details.asp?ID=1622" rel="nofollow - 54 Atom /diaries/details.asp?ID=2179" rel="nofollow - 77 Tique 64 X55 Dunphy Keep it original, Pete < |
Posted By: MdFooter
Date Posted: June-02-2009 at 1:53pm
Posted By: MdFooter
Date Posted: June-02-2009 at 1:56pm
That's the magnetic trigger version which I installed last year due to the original prestolite being beyond help. After troubleshooting some coil issues, it has been trouble free. ------------- KP 1st http://www.correctcraftfan.com/diaries/details.asp?ID=2723&yrstart=1981&yrend=1985" rel="nofollow - 85 Nautique 2nd |
Posted By: MdFooter
Date Posted: June-02-2009 at 2:03pm
Al, I was told the tranny only had 40 hrs on it when I bought it last year and I put another 40 on it last season. Fluid level is good and prop is freshly rebuilt from Delta. Like I mentioned to Joe, as I power past 4500 to 5500, there isn't the corresponding huge change in speed, so my guess is maybe high 40's but probably not past 50. Definite GPS check this weekend. You're right about the improvements. About $1500 total cost but an awesome holeshot now and a NASCAR-like sound at the higher RPMs. Just want to be able to surprise those bass boats once-in-a-while.  ------------- KP 1st http://www.correctcraftfan.com/diaries/details.asp?ID=2723&yrstart=1981&yrend=1985" rel="nofollow - 85 Nautique 2nd |
Posted By: MdFooter
Date Posted: June-02-2009 at 2:15pm
Thanks for the advice Jody. The picture is of my garage test setup. You'll also notice the coil is just sitting on the manifold since the Edlebrock switches sides with a mounting bolt hole. I fabricated a new coil bracket and reran the solid steel line from the fuel pump to the carb inlet before I went on the water. I have retained all the USCG required features of the fuel system. All good info to remind everyone about.  ------------- KP 1st http://www.correctcraftfan.com/diaries/details.asp?ID=2723&yrstart=1981&yrend=1985" rel="nofollow - 85 Nautique 2nd |
Posted By: 81nautique
Date Posted: June-02-2009 at 2:26pm
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Kevin, Hardest thing now is tuning the prop, no need to spin it that high if it's not doing any good. I think a step up in pitch would be too much so it might be time for some more cup or borrow a few props from your buds and test em out.
They do sing a sweet tune at 5500 though don't they. I still run mufflers on mine and the tone this year with my mods is much more throaty than last year. The jump in Compression ratio is the balls in my book. ------------- You can’t change the wind but you can adjust your sails |
Posted By: TRBenj
Date Posted: June-02-2009 at 3:21pm
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I would be suspicious of all your readings as well- Id verify speed with GPS and check the RPM's with a shop tach.
Like Joe, Ive found my Airguides to be very accurate once dialed in. You may need to adjust yours (I would guess theyre registering a few MPH low), but a 4mph difference in top speed is certainly in the ballpark for those mods. ------------- |
Posted By: MdFooter
Date Posted: June-02-2009 at 3:39pm
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Al, I couldn't agree more with the need for more cup.......
Seriously, the prop is probably my limiting factor (limfac) right now. It does seem that the prop is just churning the water more above 4500rpm. As long as I can get a solid 42mph for footin' I'm pretty happy. I noticed you post 300hp for your current setup. Is that dyno'd or a wag? Since you have a few more motor upgrades than I do, I am probably overstating my hp at 300, so maybe I'm closer to 275? 285? BTW, your rig is CHERRY, hope to approach that level of quality some day. I do have a video of the run with good audio, but it's tape and I don't have good video capture software. Will try to post something soon. ------------- KP 1st http://www.correctcraftfan.com/diaries/details.asp?ID=2723&yrstart=1981&yrend=1985" rel="nofollow - 85 Nautique 2nd |
Posted By: MdFooter
Date Posted: June-02-2009 at 3:48pm
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If only I had Airguides....
I've been looking for a solid 0-50 speedo to replace my Telex's since they too have seen better days and the internal movements are a bit corroded. Any suggestions? ------------- KP 1st http://www.correctcraftfan.com/diaries/details.asp?ID=2723&yrstart=1981&yrend=1985" rel="nofollow - 85 Nautique 2nd |
Posted By: JoeinNY
Date Posted: June-02-2009 at 4:31pm
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Turning that prop 5500 whether the boat is moving or not is an indication of pretty good power. Actual Horsepower is hard to guess at, and doesnt mean all that much anyway since you have to get the boat perfectly propped to have your actual max rpm equal the rpm where your HP hits its peak. I think I have had 6 props on my 83 and I only got there once.
My guess is your running just below 50 which is pretty good. If you had that boat running in the 50's you would probably know it. I kinda doubt the transmission is slipping, it would be hard for it to contiually slip a little, it would most likely degrade pretty quickly and your rpm would continue to increase. I just dont think the oj 3 blade is a great prop for the bigger boats past about 4500. All the resistance of the boat to going faster increases the forces on the blades, it is 20% more stress on the prop to go 50 on a big boat with 300 hp than it is to go 60 on a smaller boat with 300 hp. That stress increases the flex which exacerbates the cavitation. More cup will slow it down keeping the engine from making its max hp thereby reducing the flexing, but still keeping you from the theoretical max speed. The cnc 3 blade props tend to hold thier shape better and perform better all around but they are not available in higher pitches in general, the cnc 4 blades are less efficient as a rule than the CNC 3 blades but have more blades to spread the forces out upon... You need a stainless CNC 3 blade in just the right pitch... good luck ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1477 - 1983 Ski Nautique 2001 1967 Mustang 302 "Decoy" http://www.youtube.com/watch?v=cO5MkcBXBBs - Holeshot Video |
Posted By: 81nautique
Date Posted: June-02-2009 at 6:30pm
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Good points from Joe as always.
If he's only running 50 at 5500rpm he's got over 26% of slip and would add some validity to Joe's flexing scenario. With that sort of movement going on it's a matter of time before a blade fatigues off. I had a similar conversation with Bill Weeks of ACME yesterday. He said adding enough cup to my 540 would probably end in a stress fracture at the tip of the blade. His only option for me is the 1598 which is a 13x14 designed for the big blocks and I doubt I could jump 2" in pitch and have good results. May be time to look at another brand of CNC prop. ------------- You can’t change the wind but you can adjust your sails |
Posted By: JoeinNY
Date Posted: June-02-2009 at 6:40pm
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Yeah alan I still have been attempting to comment on your thread but its long and involved and I never actually get the time to send it. The short story is the best cnc prop I ever ran on 83 when it was a 1:1 was the Acme 431. 13x13x1... problem is it is a LH and they dont make the right.. dont know why not. Best prop I ever ran on my 67 is a OJ xmp 3 blade, also a LH not available in RH. Why these guys are against us CC guys is anyones guess... Alan's situation is different then here, his boat is faster but he is starting to see the same limits. I dont know how much of the loss up high is flexing and how much is slippage, either way the problem remains too much water force on the same blade area. Makes a guy kinda want to run a well built and balanced engine with a single plane manifold and let it turn a bunch of rpm with a smaller prop pitch.
Sure is disapointing when 600 rpm gets you another 1.2 mph but I have seen it. ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1477 - 1983 Ski Nautique 2001 1967 Mustang 302 "Decoy" http://www.youtube.com/watch?v=cO5MkcBXBBs - Holeshot Video |
Posted By: Luchog
Date Posted: June-02-2009 at 9:17pm
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I'm not sure that current prop manufacturers are really designing their props to be fast... I guess pulling power is what they are all about and not top end speed, I'd not bet surprised if you tested another blade design and have completely different performances.
Another issue with your props cavitating is that once the cavitation starts you get more rpms that a non cavitating prop. So a better bitting prop the same size may turn fewer rpms that one wich does. ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=2095" rel="nofollow - 1980 Ski Nautique Commander 351W |
Posted By: MdFooter
Date Posted: June-10-2009 at 1:57am
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Well the weather held for a while on Sunday but I only had a GPS unit to verify actual speed, no shop tach to verify actual RPMs. I added a youtube link for a crude video, but decent audio.
Here are the results: 3000RPM = 30MPH 4000RPM = 38MPH 5000RPM = 42MPH 5500?RPM = 45MPH From this data, it would appear that the stock OJ 3 blade prop is definitely cavitating proportionally more as the rpm increases, since the speed increase dramatically drops off after about 4000rpm. Questions: Would increasing the cup enable better bite at the higher rpms? Would a better quality prop at 13 pitch hold the water better also? I'm not looking to push past 50, but I would like the prop to be efficient in the low 40's for footin' once in a while. Thanks for all the great advice so far, the forums are great for helping each other out. ------------- KP 1st http://www.correctcraftfan.com/diaries/details.asp?ID=2723&yrstart=1981&yrend=1985" rel="nofollow - 85 Nautique 2nd |
Posted By: Luchog
Date Posted: June-10-2009 at 4:46am
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I think you could either try a slightly larger pitch prop or a cupped one as well. ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=2095" rel="nofollow - 1980 Ski Nautique Commander 351W |
Posted By: JoeinNY
Date Posted: June-10-2009 at 11:52am
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Definitely sounds like you could see some benefit with a better prop. I have the same hull and would see 50.2 at 5300 with the LH version of a 540. I would verify actual rpms first then save up some money for a new prop. ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1477 - 1983 Ski Nautique 2001 1967 Mustang 302 "Decoy" http://www.youtube.com/watch?v=cO5MkcBXBBs - Holeshot Video |
Posted By: MdFooter
Date Posted: June-11-2009 at 1:16am
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Well as luck would have it, I do have an ACME 542 RH prop that came with the boat. 13X11.5, .080 cup. I had it redone by Delta last year since one blade had a beautiful parking lot bend in it but I never used it because I thought 1.5 inches shorter in pitch would over-rev the motor. (Too many years with outboards) But Joe, if you're swinging a 540 (13X12) with 400HP, then surely I'll be fine with 11.5 on my 285ish? motor. I'm going to go put in on right now!
BTW, your motor build story was my inspiration to start building new life into my motor, until I realized you made a std rotation! I'm stuck with RH.  Any good sources for RH parts like camshafts and cranks?------------- KP 1st http://www.correctcraftfan.com/diaries/details.asp?ID=2723&yrstart=1981&yrend=1985" rel="nofollow - 85 Nautique 2nd |
Posted By: Luchog
Date Posted: June-11-2009 at 1:30am
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Md, you could try the 542 to see how the different blade shape/prop construction behaves on the RPM range.
Anyway it's not apples to apples since the Acme might cavitate less, creating more load and decreasing rpms, but it's 1 1/2'' shorter than what you have now. It will set the bar to guess for the Acme props. ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=2095" rel="nofollow - 1980 Ski Nautique Commander 351W |
Posted By: JoeinNY
Date Posted: June-11-2009 at 1:48am
I was at one point swinging a 541 which is the lh version of the 540 and the numbers were as above, I included them as reference for speed to rpm with that prop. I then made some changes so my secondaries would open all the way and switched to a 431 which was a 13 x 13 cnc prop, that was the best runner I had as a direct drive prop and would see an occasional 52.8 at 5100 rpm. Since then I switched transmissions and have been pretty much left to 4 blade props. RH parts are available, with the exception of a reasonable price roller cam. I dont see why any local machine shop couldnt polish the crank backards for you polishing is that complicated. I think you have a runner now you just got to have a better prop, try the 542 and keep your eye on the rpm but at 5500 you should be better than 45mph even the 542. ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1477 - 1983 Ski Nautique 2001 1967 Mustang 302 "Decoy" http://www.youtube.com/watch?v=cO5MkcBXBBs - Holeshot Video |
Posted By: MdFooter
Date Posted: June-11-2009 at 2:07am
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Well less cavitation should mean there's a more consistent load on the motor hopefully translating into better efficiency?
One more motor question Joe. Hopefully this is a short answer. Besides the obvious in water pumps and fuel systems, what are the big differences in a marinized motor? Specifically are the pistion wall and ring clearances different for a marine application? Will fitting a std. block with automotive pistons be just fine in a boat? I can't remember if you mentioned that in your engine build post. Thanks again for all the help! ------------- KP 1st http://www.correctcraftfan.com/diaries/details.asp?ID=2723&yrstart=1981&yrend=1985" rel="nofollow - 85 Nautique 2nd |
Posted By: JoeinNY
Date Posted: June-11-2009 at 4:14am
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water pump, fuel system, marinized dist, and alternator, other than that ... yeah no short answer, same exact block just prepped a bit differently. Piston to wall clearance depends somewhat on the piston but in general marine is always more, same with ring gap in particular on the top rings again there quite a few factors. A good machine shop will bore and hone the cylinder walls to whatever size you tell them and you can file the end of the rings to get you where you need to be. After all that use some brass freeze plugs and run it. Everything is discussed in detail on this site somewhere, but if you have specific questions when your getting into it just holler, or call.
------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1477 - 1983 Ski Nautique 2001 1967 Mustang 302 "Decoy" http://www.youtube.com/watch?v=cO5MkcBXBBs - Holeshot Video |
Posted By: Luchog
Date Posted: June-11-2009 at 1:55pm
If the prop is cavitating then it's working on air, therefore spinning easier. If it's pushing through water then it's working on load. ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=2095" rel="nofollow - 1980 Ski Nautique Commander 351W |
Posted By: MdFooter
Date Posted: June-16-2009 at 12:27am
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OK, so I get the n@@bie of the year award, seems all this time I had my best prop sitting on the damn shelf! What a difference with the ACME 542! Smooth, vibration-free pull from idle all the way up through 40mph.
The results are the same for less than 4000RPM, interesting with 1.5in less pitch. But after that is where the 542 makes the money. 3000RPM = 30MPH 4000RPM = 38MPH 5000RPM = 45MPH 5300RPM = 48.5MPH! I could definitely feel much less cavitation at the higher rpms. Even though I still had plenty of throttle left at 5000, when I punched it the rest of the way, the speed and rpms built more slowly, translating into a real speed increase and the GPS verified that. So even though max rpms are less, it means the prop is staying hooked up at that speed and the rpms are conveying into real speed. I would say a solid 48mph isn't too shabby will a full tank of gas, 4 people, ski gear and the rear seat in the boat! Thanks guys! ------------- KP 1st http://www.correctcraftfan.com/diaries/details.asp?ID=2723&yrstart=1981&yrend=1985" rel="nofollow - 85 Nautique 2nd |
Posted By: 81nautique
Date Posted: June-16-2009 at 1:46am
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Haha, yes but the Noobie of the year award is a traveling tribute to the trials and tribulations of those willing to venture out with nothing but faith in the experiences of others and the hope that they will step up and confess their darkest secrets(mistakes)..
You won't hold on to it for long so enjoy. Now 2 comments, if you ever get your hands on a 540 please throw it on. Second,what thrill it will be to foot behind such a responsive boat. Nothing like a quick throttle burst to get you to 40+ in the blink of an eye. enjoy ------------- You can’t change the wind but you can adjust your sails |
Posted By: JoeinNY
Date Posted: June-16-2009 at 2:05am
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I agree with Alan on all accounts, I only add that in hindsite reading the post the fact that the original OJ had been reworked should have been a giveaway that it was not quite right. A good legend 13x13 should not have been that far off. Thats a strong running 2001. ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1477 - 1983 Ski Nautique 2001 1967 Mustang 302 "Decoy" http://www.youtube.com/watch?v=cO5MkcBXBBs - Holeshot Video |
Posted By: Luchog
Date Posted: June-16-2009 at 2:10am
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It's always interesting to get the results for this comparations, It's pretty impressive how efficient this ACMEs are.
My 542 also performs 1-1 between 2600-3500rpms, it seems the prop likes that running angle/altittude to work best. I also believe the 540 is the ticket for you. ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=2095" rel="nofollow - 1980 Ski Nautique Commander 351W |
Posted By: MdFooter
Date Posted: June-16-2009 at 9:33pm
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I agree Al, having a whole fist full of throttle left after getting to and maintaining 41mph (my preferred bf speed) was one of my goals. Wasn't sure if I'd get there with just heads and a manifold.
I'll keep my eyes open for a 540, but I'd rather have a new boom first. 
I've had Delta propeller refinish both props but it was mostly just cleaning up the edges. Is there a better place to send props? ------------- KP 1st http://www.correctcraftfan.com/diaries/details.asp?ID=2723&yrstart=1981&yrend=1985" rel="nofollow - 85 Nautique 2nd |