Propping for a heavy guy that wants to ski

[JustJason]

Anybody know of the best ones? I need to pick out a prop for a guy and it's going to be an oddball. Merc wasn't much help on the matter.

Anyone here 300+ lbs... Like linebacker size... water ski?

 

[Silvertip]

Re: Prop selector/prop calculator websites.... Any big guy or prop gurus around here?

Re: Prop selector/prop calculator websites.... Any big guy or prop gurus around here?

I use this one but you can google or yahoo search for "Boat Prop Calculator" and find many others.

http://www.rbbi.com/folders/prop/propcalc.htm

 

[steelespike]

Re: Prop selector/prop calculator websites.... Any big guy or prop gurus around here?

Re: Prop selector/prop calculator websites.... Any big guy or prop gurus around here?

As far as a prop calculator pick it.
your results are only as good as your input.And they do tend to be optimistic on the high side.
There are lots of folks here that can help if you can supply the info we need in the stickies at the top of the page and the helps on the prop store page.

 

[180shabah]

Re: Prop selector/prop calculator websites.... Any big guy or prop gurus around here?

Re: Prop selector/prop calculator websites.... Any big guy or prop gurus around here?

Do you have any baseline info from the current setup?

 

[JustJason]

Re: Prop selector/prop calculator websites.... Any big guy or prop gurus around here?

Re: Prop selector/prop calculator websites.... Any big guy or prop gurus around here?

Unfortunately no.

Here's the deal. Late 1970's something Baja 19 foot bowrider with a GM V8.
Owner said it was an 01, ran rough, wants me to come out and look.
01 turned into 91, which turned into 81, which going by the manifolds on the thing, looks like 77-79.
Normally I would have punted the job, but the boat belongs to a guy whose dad owns 3 newer boats, all of which I service.

Got out to the boat, doesn't start, no tags/serials on the engine etc. Could be a boat motor, could be a junk yard dog. Again, I really should have punted the thing but the guy agreed to some work with no garantees on overall performance because of all the unknowns.
Started with a comp test, the on to a full tune up, R&R'd the fuel line and fittings, along with a couple of knick knacks. Engine runs great now. WOT RPMS unknown at this point, (bad tach) and I'll have to sell him one before I can pick a prop. By feel only, it feels like it's probably a 5.0. Pulls hard but not hard enough to be a 350 in a 19 footer, and I know i'll need a tach, but sounds like it's hitting WOT.
Like everybody else up here, owner doesn't "want to sink a bunch of money into this thing". But he's going to need a tach.
Prop on it is dinged up pretty good, no markings on prop or outer inner hub for dimensions, haven't pulled the prop yet, wasn't going to bother with needless things unless I had her up and running.

So right now i'm calling this thing a 19 bowrider, 5.0 4BBL (Merc 898 I think) I'm thinking it's 220ish HP. It has a 1.32 (somewhat uncommon) gearcase on it (or so it's stamped) and a 3 bladed tin prop. Guy wants to water ski, guy is the size of a linebacker, 300+ pounds.
Any ideas of where I should start, 4 blade prop of appropriate dimensoins, or should I stay with a 3 as a ski prop only (that would obviously over rev the engine if allowed to)
Thanks

 

[180shabah]

Re: Prop selector/prop calculator websites.... Any big guy or prop gurus around here?

Re: Prop selector/prop calculator websites.... Any big guy or prop gurus around here?

Lots of ifs here, but if the engine is getting to the proper WOT range, and the top of the range is preferable, and IF he's not adding a bunch of gear and 800lbs of spectators then stick with the same pitch Amita4.

If he is serious about watersports, and is even remotely thinking about try to get up on a single ski, then he needs to drop pitch, or even better would be a high-five with PVS.

Like you said though, without a tach, this is all just waggy....

 

[JustJason]

Propping for a heavy guy that wants to ski

I know... way to many if's on this one. Which is why I turned here.

1/2 the problem is even with a good tach, the old prop is digned up so the engine may hit WOT only because the prop is slipping so much.

If I can get dimensions on the old prop, and replace it with a new identicle one, the rpms will go down, only a question of how much. It may be enough that the engine is now under rpms. If that happens then I have to figure out if its still a prop problem, or a fuel problem, or an engine problem (ie- car engine, cammed wrong).

But if I underprop it for skiing, the engine will obviously over rev. Unfortuneately i'm not a dealer and I can't be switching props left and right.

 

[trendsetter240]

Re: Prop selector/prop calculator websites.... Any big guy or prop gurus around here?

Re: Prop selector/prop calculator websites.... Any big guy or prop gurus around here?

Too many unknowns to make an accurate prop selection. Without knowing the current prop pitch and WOT RPM it's going to be a guessing game.

1.32:1 gears means that prop will likely need to be in the 15p range, perhaps even a 13p to pull a 300+lbs skiier.

Can you take a shop tach or one of your own on a test run just to get the numbers with the current prop? You need to know what the WOT RPMs are with an average load to determine what prop will work best for skiing as well.

Definitely a 4 blade, solas amitas are the least expensive and are very good overal props.

HTH

Cheers