high altitude props
 

I just bought my first big boat - a 1995 31 ft warlock sxt cat with two paul phaff 600 hp 502's in it. It has 4 blade bravo one 28 p props on it. At sea level it does a gps of 100mph at 5600 rpm. But, at lake tahoe - 6250 elevation I would be un neccessarly pushing it to get past 4500 rpm. I was not paying close attention but it looked like I was doing 75 to 80 mph. The previous owner told me I needed 24 p 4 blades. He also told me he grenaded drives with 3 blades when they came out of the water and then re entered it so he replaced the drive shafts with special steel shafts and the 3 blades with 4 blades and has not had any problem since. My question is that there are so many types of blades out there, lab finished, stock, 5 blade, larger and smaller, and I have no knowledge of props. Any suggestions or companys I can contact for advice? What kind of performance enhancement can I gain with a lab finish vs stock?

Yes


There are many options and many tales. Usually the tales come from the seller........(especially when it involves top speed capacity HahHA)

Anyway, 4 blades create more load on drives than 3 blades but I don't think that is a issue here.

Call us and we will answer all the questions you have to the best of our ability.

Brett

Rick, Call Brett, he is a great guy and will answer all your questions with no B,S. He does all my prop work. Doug

I was impressed with the previous owner, with his honesty and candor. So much so that I didn't even test ride the boat - just started the engines in the driveway! Neither of us wanted to freeze in the ocean breeze that morning and I had a 10 hr + drive back home in front of me.

He told me that the boat would do 100 at sea level, at 5600 rpm, from his GPS ( Which he is sending me). At Tahoe, elevation 6250 ft I got what appeared to be an indicated 75 or 80 mph at 4500 rpm in 3 to 4 ft chop from the liquid filled speedo on the dash. It didn't seem to want to go past 4500 rpm and I didn't want to push it - knowing full well it has props that have way too much pitch for this elevation. The previous owner said I should not take it past 5600 and that the rev limiter will cut in at 6000. Additionally, he said to NOT push it at this elevation with the current props.

I should have a GPS in a week - waiting for it to show up. Now the question is, just how long do I have to wait for warm weather at one of the surrounding lakes? I know Tahoe will not warm up until July, June if it is a warm spring....

Brett, I will call you next week after Christmas!

Rick

Thats a lot of chop:eek:

I would think there are still some nice days to get your props dialed in this winter. I'm @ 5' myself & will pull the boat out in February on the occasional nice day. Once your used to draining your blocks, etc you can knock it out in no time.

I normally run a labbed 26p, but In Tahoe I run a reg B-1 24p .I'm not getting max performance with it, but it runs good for the change in altitude.

I have done this twice so I am getting better. The local boat shop here suggested that I put in Sierra antifreeze ($16 a gal!) down all four hoses going to the top of the thermostat housing until it spilled out. I did, a total of 5-6 gallons, after draining all the water from the blocks by removing the water pressure sensors. I also blew a lot of air through the exhaust hoses to clear the exhaust of as much water as possible before adding the antifreeze. If I get a nice day, I am going to travel to Folsom lake - a 2 hr drive, and see what this boat will do at sea level.

Well, if you are going from a 26 to a 24 and it helps but you need a little more, then my going from a 28 to a 24 should be about right? I will wait for Brett to call me!

Rick, The motors will make more h.p. with the cold dense air than they will on a 95 degree summer day or even an 80 degree Tahoe day. Find some props that are close and go from there. I would test at sea level to get a baseline speed verse rpm with the 28's. My previous boat was a 1989 27 daytona with twins, about 500 h.p. each? With 1.50 gears and 30 pitch bravo 1s my top speed was 82mph. The boat bottoms I think are pretty similar as are the weights. I ran 26 bravo's at Tahoe but had 1.50 gears. Top speed is not really where you boat. I run different props for different runs. I may run tall props for a run to San Francisco and smaller props for a delta run. More starting and stopping. Brett will steer you in the right direction. Doug

Thanks Doug! This boat has 1.38 gears in it with 28 bravo ones. The motors are supposed to have 600 hp each. They certainly have a lumpy cam in them. I have the dyno sheets from Paul Phaff saying they they have 606 and 597 hp/ over 600 ft lbs at 3000 rpm and the receipts for oversize valves and for the new valves and seats, cam followers, and about $3000 worth of porting on the heads and intake manifolds. There are also receipts for the recent top end rebuild (about 20 hrs ago) for new valves and valve seats, etc.

All I can say is that even knowing that typical boat speedos are inaccurate, the one in this boat is oil filled and said we were doing about 75 to 80 mph in what appeared to be fairly decent chop - I estimate it was 3 or 4 ft - we were going pretty fast - we were in the middle of lake tahoe at about 1:30 pm and the wind had come up as it usually does. It felt as if we were driving my 2500HD on a rough stretch of I 80! Not to bad. The tachs said we were at 4500 rpm and it would be pushing it to hold it to see if we could get any more rpm out of them when they were obviously straining due to the high gearing of the props.

With my very limited experience of about an hour an a half of run time with this boat, the previous owners claim of 100 mph at sea level still seems in range. I say this thinking that even if I was doing 75 mph, that if I had another 1100 rpm and was at sea level, how much more MPH could I get? Another 25 mph? Maybe? Also, the air being denser at sea level means I would get much better lift! This too would improve this boats performance.

Tell you what, lets wait until we get some warmer weather in Folsom and meet at Folsom Lake dike 8 and put this in the water and find out! Folsom is at 400 ft elevation I think so that should be great. By then the GPS should arrive in the mail too.

In fact, the previous owner is a member on this forum I will contact him and see if we can get some more info from him and his open ocean experience with this boat! Just google "31 ft warlock cat" and you can see pictures of this boat completely out of the water coming out of a swell.