500hps rebuild

[Thunderman98]

Thunderstruck,
Thanks for the info. I also have the LWP and a very high X-Dimension. I was also looking at putting the Imco Standard Lowers on if I can find a good price. I am just looking for the caseings if you happen to know anyone that has a pair. I would like to break the 100 mph mark this year. I dont think I will have a problem doing that with the power I have, Just need to get my slip numbers down about 6-7%.

[Thunderstruck]

OK here's a nose cone picture.

[Thunderstruck]

See the hole under the point for the water flow? You drill the front of the drive and there is a 1/2" piece of tubing that goes from the hole in the nose cone to the hole you drilled. You cover the openings in the tube with tape and epoxy it onto the drive. Don't let epoxy squish up through the existing LWP holes in the drive and block the water flow like I did.

Now the rest of the story. It looks like that when I trim the drive out the point deflects water away from the water inlet based on high oil temps at high speeds that I did not have before the nose cones. SO, since I have my drives up to Mr. Gadgets for rebuild so he is going to drill holes in the sides of the drive cases to make my drives DWP's. Not hard to DITY but since he has the drives anyway. Also, there is a thread on OSO discussing the nose cone water pickup. FYI the thread also discusses the IMCO lower having the same problem. Don't know the specifics but you may want to search the drive section of OSO.

[Thunderstruck]

One issue I had before the nose cones that seems to be the clue that the existing Bravo bullet is building a pressure wave and deflecting water away from the prop is that my speed did not change proportional to the prop pitch before I got the cones. I stayed about the same speed with 28s non labbed and 30s labbed (within 2 mph) just a little more rpm but not what the slip calculations predicted. Now the 28 Nonlabbed only gets to 86 or so while the labbed 30's get to 90-91.

Also, all this assumes that the drives are not being over trimmed?? Right??

[Thunderman98]

Thanks for the info and the pics. I wonder why they did not add the slots for the LWP so you would not have to drill the hole. With you drilling the holes in the side of the case, My concern would be once the drives are far enuff out of the water, you may not pick up any more water flow, but then start drawing air pockets between the the 2 pickup points and creating a overheating and possible impeller issue by not having a continuious water flow to the engine. What has Dick said about this, and is he drilling the holes farther down or are they being drilled in the same location as a factory Merc drive.

[Thunderstruck]

Thanks for the info and the pics. I wonder why they did not add the slots for the LWP so you would not have to drill the hole. With you drilling the holes in the side of the case, My concern would be once the drives are far enuff out of the water, you may not pick up any more water flow, but then start drawing air pockets between the the 2 pickup points and creating a overheating and possible impeller issue by not having a continuious water flow to the engine. What has Dick said about this, and is he drilling the holes farther down or are they being drilled in the same location as a factory Merc drive.

On OSO there are a couple of guys that have fixed oil temp issues with these holes. It's either that or transom pickups for me so I'm at least going to try the LWP modified to DWP.

[rssteiny]

So with 430 hours and springs done at 260 if my leakdown numbers are good like 10% or less and all the same give or take 1 or 2 % ,,what do you think about leaving them alone another year, these motors have always had royal purple oil and changed every 20 hours,, it still runs great with max oil pressure as it always had,, and uses about 1/2 quart oil between changes. if so i can focus on nose cones and my slippage problem and rebuild the way i really want to next fall and winter as spring is getting close.

thanks

[Griff]

I would run it again this year with those numbers. I would only do a refresh if you plan on keeping it for a least a few more years.

Figure this. If you put 10-12k into the engines now, you'll be lucky to recover any of it on the resale if you sell it next year. A potential buyer can use the engine hours as bargaining chip. Even if you came down 10k on your wanted sale price, you would still be even.

[Thunderstruck]

I agree with Griff.

BTW, why do you think you have lost the 87mph to 84 mph since you bought the boat?? 87 is probably the fastest 500HP 32 I have ever heard of so, A. I'd like to know what is different about your boat than mine. B. with 10% leak downs it isn't the motors. Did you change props?? I struggled to get over 87 with a lot more hp.

I heard my boat did 83/84 new from Clark and Chuck Beecher but it had a pitot tube speedo, not GPS. My boat did have labbed props that I had up to 82 (pitot speedo) but one of the blades cracked so bad I had to scrap the props so I never got above 81 with regular B1 28's.

[rssteiny]

the boat was origianly joe skrocki and he had done some carb work , msd boxes and really had it dialed in, the boat ran 87 on gps at 5500 rpms with 30 p b1s labed. it still rins 83 to 84 all day at the same rpm and props, the one prop needs redone as it has a chip in the edge all last year. so if im running 84 at 5500 rpm with 30 p labed b1s you say my slip is 17%, should i try a nose cone and a little prop work??? This boat ran over 90 new i have the article on it in performance boating and i spook to the guy at active thunder a few years ago that test ran it at 91.3 on gps.

ps
also i added a 4" wind screen that may of slowed me down a bit

thanks Rick

[Griff]

I'm pretty sure Joe did some work to the bottom on Audacity. Nothing major, but something close to blueprinting it. I remember he did a lot of work with tweaking and testing the props as well. If the props haven't been tuned up at all, that could be part of the reason for the 3 mph loss as well. I think Audacity has actually gone over 90mph with some other props.

It could be 1mph caused by the windscreen addition, 1 mph caused by the props needing a retune, and 1 mph due to a very slight loss in HP from the hours.