500hps rebuild

[rssteiny]

My 2000 500 hps carb motors have 430 hrs , still run flawless and strong but i want to refresh and power up a bit. what would be the best way to go.

[HolyMoses]

I had the same motors in my 36OL. As long as you keep the valve train fresh every 300hrs. and maintain the motors you should see 800 plus hours with no problems to the internals of the motors. If your looking to refresh them you could do new bearing upgrade the rods, heads and cam and make an easy 550hp to 600hp.

[Griff]

Bump comp ratio up to about 9.25, aluminum AFR heads and a cam change. I would guess about 575hp.

[rssteiny]

What about the bottom end

[Griff]

The rods and crank are fine to handle the HP increase. Just have them polished and reconditioned as needed. The comp ratio increase would be achieved with new pistons.

[Thunderstruck]

Deck the block or mill the heads to increase compression ratio with the stock pistons, rods and crank. Up the compression with your iron heads will gain some hp with little $. I think .01" off of the heads or the block will raise the compression by .1. Also, port and polish heads with new cams can help without expensive aluminum heads.

More $ but AFR heads and RMBuilder cams can make 600+ hp. I made 595 hp with stock rotating assembly. Need to bump compression to 9.6 with aluminum heads. The best I have heard with AFR heads and RMBuilder cams is 640 hp. Need to turn up to 5800 rpm to get >600 hp so you will need new ignitions due to the 500 hp rev limiter. I went with Crane that will work with the stock Merc hall effect distributor. Need to seriously consider closed loop cooling if you boat in brackish or salt water with aluminum heads.

My 1998 AT runs 91 with Gil Exhausts.

Basic freshen job would be new springs, lifters, rings, hone block and crank, new bearings, valve job. New roller rockers may be a good idea also.

We can discuss live if desired. Let me know.

[Offshoredrillin]

I have a set of heads off of my 500 efi that have already been milled to bump the compression up to 9.25. one set is fresh 0 hours, the other has 45 hours....1800.00 for both.

[Griff]

His boat is 100% dialed in with props and carb tweaks and ignition already. The valve springs were done about 200hrs ago.

[rssteiny]

His boat is 100% dialed in with props and carb tweaks and ignition already. The valve springs were done about 200hrs ago.


Yes as griff said it already has msd to override limiter, carbs have been worked, and with labbed 30 props i run 5500 at 84mph. would like to refresh due to hrs being 430 and would like to run 90 mph, and yes springs were done about 250 hrs ago so also time to renew them as well.

[Thunderstruck]

Yes as griff said it already has msd to override limiter, carbs have been worked, and with labbed 30 props i run 5500 at 84mph. would like to refresh due to hrs being 430 and would like to run 90 mph, and yes springs were done about 250 hrs ago so also time to renew them as well.

Your theoretical speed is 101.5 mph which makes your slip 17.3%. That is high. You could get more bang for the buck going after the slip ie making the hull/drives more efficient, than adding hp. I added nose cones to go from 87 to 91 mph. My stock 500 HPs pushed me to 82 mph best. Motor mods got me to 87 (5500 rpm) with 16% slip. Now I'm at 5450 rpm with labbed 30" props at 91 mph which is 9.5% slip with the nose cones. Big difference.

One guy with a 32 AT I talked to had his hull straightened and gained 3-4 mph. Have you checked your hull with a long straight edge to make sure you do not have a hook?

In my opinion, the more hp you throw at your hull/drives, the more slip you will get since you are already at 17%. My problem was that at 87 mph the pressure wave on the front of the nose of the drive case was pushing the water away from the props to the point that the slip went up and killed my hp increase. The faster you go the worse it will get with the Bravo outdrives. Nose cones fixed my issue. The hp to make 90 is therefore a moving target with a situation like you have. I will take much more hp to produce 90 mph at >20% slip than at 10% so take the easy speed and improve your efficiency before turning the hp up.

Based on my 1998 32' AT that runs 91, you will need 585 crankshaft hp on a dyno with no accessories, using dyno exhausts to make 90 mph low on fuel by yourself in the boat. (That assumes 10% slip.) Adding water pumps, power steering, alternator, marine exhausts and the drives consumes hp but my dyno did not have the capability to dyno a fully dressed marine motor. I would shoot for 93/94 to make 90 with a tank of gas, people and gear.

Ambusher, the guy on BoatFreaks has a set of stroked 454's, 496 ci motors that runs 92 or so. He probably has a good bit of hp than me but close so there you have two references with the same boat that indicates you will need close to 600 hp which will be difficult without some head work or new heads and new camshafts and some dyno time.

Nose cones were <$500 doing the work myself. Cheapest speed I ever got.

Once again, PM me and we can talk live. I've been there done that.

[Thunderstruck]

BTW call RMBuilder for the HP possibilities, he is the 502 NA guru for cam shaft/valve train improvements.

If you are interested in aluminum heads, my experience with AFR was/is great. They are some of the best heads out of the box to build a torque monster combined with RMBuilders cams. My acceleration is amazing, ask Clarkstar.

[rssteiny]

BTW call RMBuilder for the HP possibilities, he is the 502 NA guru for cam shaft/valve train improvements.

If you are interested in aluminum heads, my experience with AFR was/is great. They are some of the best heads out of the box to build a torque monster combined with RMBuilders cams. My acceleration is amazing, ask Clarkstar.

Is there a difference in the 1998 32 and the 2000 32 hull. nose cones that is interesting and makes me wonder if that would help me. thanks rick

[Thunderstruck]

Is there a difference in the 1998 32 and the 2000 32 hull. nose cones that is interesting and makes me wonder if that would help me. thanks rick

I don't know if there is any difference in the year models. I do have a notched transom with fairly high drive heights which I would imagine you have also.

Tom

[rssteiny]

I don't know if there is any difference in the year models. I do have a notched transom with fairly high drive heights which I would imagine you have also.

Tom

Yes i do as well, im just asking because if you have the same hull then i may want to try the nose cones, i was thinking that 1999 or 2000 there was a change in the hull but im not sure.

[Griff]

I don't think they ever changed the 32 bottom other than the notch. My '97 does not have a notch, but I have boxes instead. My slip is right around 12% and I do have nose cones as well. The only other difference I have seen in 32's is the slant on the deck at the stern that started in '98, I think.

[Thunderman98]

Tom,
What nose cones did you use. Right now my best speed is 93 radar and that's with 700hp dyno 572 motors at 6000 rpm. I was spinning 30's at 6000 which put me around 18% slip. I did try a set of stock 32's, but popped a drive at 3800 and roughly 70 mph. Im hoping to retry again this spring with the 32's to see what my top speed and slip is. I know we have talked before, but cant remember what you had said.

[Thunderstruck]

thunderman, guess I haven't been watching this board enough and missed your question. SORRY!

Background, I have LWP Bravos with a notched transom and fairly high drive height. In fact my 32 was supposedly the first 32 with the notch. Anyway I called Teague who recommended the "Leading Edge" nose cone that fit the LWP drive. It is pointy, not crescent shaped like a hydromotive cone. Look in the teague online catalog for the model. The drive height has a lot to do with the type of nose cone you need so ask around before plunging in. The sales person at Teague was very knowledgeable regarding nose cones and they let me talk to a shop guy who helped me with the installation issues.

[Thunderstruck]

I couldn't post a pic of my drives with the cones on but look on OSO or boatfreaks. Must have to pay to get pics on on SO or am I missing something?

OK I got it. Didn't scroll down far enough.

[Chris]

No- costs nothing to post pics. You do it exactly the same way as OSO or BF.

[Chris]

On this rebuild project, you can get SCAT kits for under $1800 that will turn those engines into 540's. ATECO is running a sale right now.

There's no substitute for cubic inches and in a boat, there's absolutely no substitute for the additional torque you get with a longer stroke. Stick a set of Dart 320's on them and the Dart manifold and you're set. I'll second calling Madara for the cam.

[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. :o

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.