First time out
 

took the new new toy out today for the first time since I test drove it in AZ.

picked up some 30p B1's out of the classifieds and ran a 95 on gps, 5000 rpm. First cat and I love it!

what small simple mods can I do with 500 efi's to pick up some speed? :readinghelp: boat has extension boxes.

looked great, congrats... your now infected the disease (known as never fast enough):drink: next step triple digits

what small simple mods can I do with 500 efi's to pick up some speed? :readinghelp: boat has extension boxes.[/QUOTE]

wipple chargers:eek:

arizona speed & marine makes a kit to bump the 500efi's up a bit

any of the below will work depending on your budget.

hp adds first...
raise x up.....
add prop blades to get the boat to bite when you raise x too high...

Don

nose cones or sportmaster lowers will gain some mph.

me..... I would get the shortest shorties I could find and put them on and start dinging with the props and get it as fast as I could that way FIRST..... Then some winter start modding the engines depending on just how fast you want to go.....because I like to relax at the lake, I don't have a team of guys around to change out extra motors when i pop them..... keep the engines as turn key as you are willing to for speed.

Don

:worthless_without_p

If I am running a 1:50 drive with a 30p @ 5000rpm would I gaing anything out of a 1:36 (mph)?

Im going to put a pair of shorties for this summer. What can I expect from this? 3-4 mph?? or I am I dreaming......:eek:

at this power, you will slow down by going to 1.36 gears... you don't want to change gears until you need to go higher than 34 props. depending on where your x is now i think you can get 3-4 or more by raising your x...
Don

what's the max hight for the X? the center of my prop shaft is about 1" higher than the bottom the sponson. If I put 2" shorties on that would bring me to 3" higher????? this is new to me....

Thanks


Phil

you will never get on plane with 4 blades & being 3" above the sponson, I believe you are at the optimal position 1" above, all you need now is more HP:lolhit:

I would try it with the 2" shorties.. and get some 5 blades... you may have to put in some 1" spacers in, but I would try it with the 3" and play with props... The nose cone on the shorties will help out too.

Don

Don, I think Randy is right about being too high. I can't spin my props over 5000 w/ 30p 4 blades, if I add a blade this will make things worse??

I'm going to leave the motors for the summer and possibly put some whipples on in the winter.

I have a serious case of "NFE"! :eek:

you are right about adding a blade at that height, but if you raise the x up, you will need the blade to get the bite and ultimately you will speed up.

there are boats out there running with 3" above and they are using 5 blades to make it work. I would not recommend that setting if you are running high hp... because the boat will get too loose, but with 500's you will optimize your speed by going that high and getting the props to work with you there......

good luck
Don

thanks for the input Don.


When are you going to get back into a cat? :boat:

The reason Don is saying to try shorties is because of the boxes. Most of us do not have have boxes and even or a little above is about perfect with that config.

i personally picked up 9 mph with -2 shorties with no boxes and absolutly no other changes. With that being said my boat really frees up around 95 mph which is where I was stuck prior to the shorties. Mine is a 98 so is probably similar in weight to yours.

Also 95 mph at 5000 rpm with 30 pitch props and 1.50 drives would be zero slip. This is not likely. Some number somewhere must be off.

Phil, The picture of your outdrive leaves me with the idea that those ext boxes are stellings. If so, they have a limited vertical movement/adjustment. In general terms (jump in here guys if my info needs correcting) the IMCO and Stelling in the neutral position will give you a 1" drop of your prop shaft vs. having the Bravo transom assembly mounted directly to the transom.

So, what is the common X dimension of an AO with a Bravo 1 with a standard lower? I am trying to figure out the -1" dimension with your standard lower. Did AO have a factory higher outdrive transom cutouts? Or, they are Stellings positioned in the upper location?

If you do stick with the standard lowers, (as others have suggested) you will need to install a nose cone. My recommendation is the Hydromotive unit.

I was also crunching the numbers and the 30P x 5000rpm didn't get it to 95 mph (with a common slip % thrown in). My boat using a standard Bravo 1 28P prop at exactly 5000 read 78.9mph on the Garmin.

Normal is roughly 2 down. His extension boxes are probably in the 3 up position giving it 1 above.

Brian, I was wondering that myself as I used that mercury prop caculator after I went out............ how accurate is a hand held GPS?

these cat are usally 6-8 maybe 10% slip???

Phil

Handhelds are accurate. Check your ratio first. Based on the bottom side of the hatch your boat may have had blowers at some point so the ratio may not be 1.50. If it is 1.36 then your slip is reasonable and your speed is reasonable based on the data you provided. If they are 1.50 then I question rpm.

Slip depends on the boat. A wise man once told me to work on slip first and the speed will come.

I also believe he has 1:36 ratio, My Buddy's 31 Awesome w/500efi's 1:36 with stock 30P (not labbed) no boxes, runs 92-93 @ 5100 ish , correct me is I'm wrong Bill.:drink:, so having labbed B1 & boxes netted him a couple MPH

my slip # is >10%

I will check that gear ratio. I think you are right. I ran it on the prop calc. and with 9% it puts me at 95.

Randy are you going in this weekend?

My slip at WFO is much less then 10% :)

I was out for a quick ride on Saturday, I buzzed by the pier @110 :eek: felt real nice, I'll be out this week end, hopefully the weather cooperates

Nice, wish I had another 15 at the throttles:angry-smiley-044: It's been a long winter.

my gear is a 1.36.

Phil, nice carpet cleaners.

haha, I guess I should have played them before I posted......:bong:

the center of your prop shaft should be 1.75 inches above the bottom of the sponson with 12 inch stand off boxes. also should be running a nose cone. all AO 3100s prior to 2000 were set up with the prop shaft 1" to 1.5" below the bottom of the sponson. 2000 and later with no extension boxes were set up with the prop shaft level with the bottom of the sponson and 1 to 1.75 above the bottom with 8 to 12 inch boxes..

Great information as I have been following the posts.... I have had several of these 3100's and different applications in each. The question currently is I have a 2002 where the x is a bit higher as you mentioned Quest in your post. Can I get away with imco boxes and -2 sportmaster shorties and 4 blade bravos? I have also heard and experienced in my past cutting off the ring defuser to help get on plane and cut some of the slip out. I care little about my past boats as they had been set up differently, but this one is an 02 and more than likely I am looking to put stock 500efi's or preferably 575sci's. I am putting together a stock application and may boost on the power a touch to gain a few extra hp's! I have a family now vs. the old days so running 130 is less likely than my recent past. Obvioulsy I am looking to maximize performance yet still have a safe application which equals.... (wife off my a$$ and me having more fun)

cutting 1/2 to 3/4 inches off the difusser ring will give you a little more bow lift at the same trim position. this will allow you to reduce the positive trim slightly and result in slightly more speed. it will make it slightly harder to get on plane not easier. I always cut off this much from my trim rings. the extension boxes will allow you to just barely get away with the 2 inch shorties but you might have to add a 1/2 inch spacer. had one boat with the prop shaft 2 1/4 inch above the sponsons and it just barely worked. thats why I recommend 1.75 inches. 5 blade herrings will cure the getting on plane problems and might even make the 2 inch shorties work perfectly well with the extension boxes.

[QUOTE=quest;3359160]cutting 1/2 to 3/4 inches off the difusser ring will give you a little more bow lift at the same trim position. this will allow you to reduce the positive trim slightly and result in slightly more speed. it will make it slightly harder to get on plane not easier. I always cut off this much from my trim rings.

I'm in the process sending my B1 labbed 32's to merc for a tune up. Is there anything else that should be done to the props to help performance while there?

I'm in the process sending my B1 labbed 32's to merc for a tune up. Is there anything else that should be done to the props to help performance while there?[/QUOTE]

I had 34 Labbed B1's on my 31 Awesome, & I had Brett @ Bblades put a bit of cupping on the tips to help carry the bow & helped planing as well, the more leverage you have to carry the bow, the sooner you will pack more air & get out of the porpoise range, hope this helps:drink:
(BTW mine had no boxes & -2 shorties)

I had 34 Labbed B1's on my 31 Awesome, & I had Brett @ Bblades put a bit of cupping on the tips to help carry the bow & helped planing as well, the more leverage you have to carry the bow, the sooner you will pack more air & get out of the porpoise range, hope this helps:drink:
(BTW mine had no boxes & -2 shorties)[/QUOTE]

Randy, are you turning props out or in? When turning out I had more stern lift with cupped blades. When turning in it seemed to suck the stern down thus creating more natural ow lift.

I was turning out, I tried in but the boat felt weird, & there was no difference in top speed

Prop rotation on a 31' Cat
 

Anytime I see a thread or post discussion on prop rotation on one our type of Cats, I re-read the following post from the "Great Moments of Cat History" by T2x (Rich Luhrs).

.--My thoughts on "spinning" in..... Simple physics.... Right hand rotation propellers,torque (lean) the boat to the left. Left hand rotation propellers torque the boat to the right. In a twin engine boat spinning outboard or , RH on right side, LH on left, the torque of the propellers tends to return the boat to level when one side or the other leans outward. When props are spun inboard RH on left, LH on right, or counter rotated the torque tends to make the lean worse. This occurs because as a boat(Cat or Vee) leans to one side, the prop on that side buries deeper and exerts more force, while the prop on the other side rises (in some cases out of the water) and exerts less force. So...... If a RH prop is spinning on the right side of a boat leaning to the right, the prop tends to push the hull back over to the left. (spinning Outboard). If, however, the left hand prop is on the right side in a right hand lean , the prop tends to continue to roll the boat over. I submit that this is why there has been such a dramatic increase in barrel rolls (even in straight-aways) in races in recent years. When I flew over races for 16 years, I could always spot the counter rotated boats, because they behaved very differently (and definitely not better)than their properly spun (outboard rotation) competitors.
The reason that many people spin them "backwards" is the fact that on some hulls the boat may gain a mile or two per hour at top speed....or..... the boat has a bottom tune that needs more bow lift. The speed can generally be achieved in other ways without using an unnatural rotation as a "bandaid" (This is particularly problematical on stepped bottom boats that skid first, then catch suddenly, then roll outward......get the picture?)
One can re-tune most bottoms to add rocker to provide bow lift without resorting to ill advised prop rotation changes.

Did you in fact notice the bow carry higher? I am very conscious of how my boat reacts to different running conditions; ie. weight distribution, fuel load, wind direction, etc. which is why I'm so curious to your results. I spoke with Scott at Mercury racing today about cup and prop rotation and he had little to no insight as to the effects they have on our boats. I guess we are kind of on our own when it comes to propellor results. I'll post results before and after the rework if anybody is interested.

I will add this bit of information. When I first met Jim Jones at Awesome, he had spoke of racing a 31 in the Great Lakes Series (don't remember the name). He was working with Hydromotive in Ohio on his prop set-up. That definately was a bravo 1 outdrive and I believe HP500 motors.

I know Randy has spoke of Brett's involvement with his 31 and the results from his handy work.

Simply from experience, appears that there are two prop companies to go to. I do agree that there are some many variables. Weight, weight bias/distribution, and lots more.