Lake Racer with MP drag setup questions

[RUNWME]

I am brand new to the world of drag boat racing. Last weekend was my first race (finished second in River boat class)

The bug ate at me all week, so this past weekend I went and purchased a 2000 Diamond Marine/JSRE Modified Production 300 drag with 15 offshore midsection.

August 9th is my second race and I want to be as prepared as can be. I will install faster trim pump and purchase a drag specific propeller.

MY setup.

I have a 1989 STV River Rocket 4 seater. I have to weigh in at 1800 lbs for Lake Racer Class.

I had to install a 10 in jackplate to mount this drag 15in midsection on my boat. Will this much setup help me or hurt me for 1/4 mile performance versus mounting the powerhead on my 20in midsection and putting it on a 3 inch jack plate?

What prop would be best for this application? I would like to set it up to turn 10k rpms at finish line. (engine made 362 hp at 10,200 rpms)

I have 3 sets of heads for this engine. 150, 185 and 220 compression heads. I want good performance, but only want to freshen engine once per season.

I am drag newbie and appreciate any help. I was thinking a 22 pitch yamaha drag prop would be best, but that is only a geuss.

I appreciate your help in advance
David

[RUNWME]

the boat...

[RUNWME]

out with the old 2.5 carb engine.. in with the new (to me) 300 drag

ALSO !! I need a extension for the tiller arm to mount my hydraulic steering. ANY one have one?

David Bunn
252-341-5126
[email protected]

[Raceman]

RunWMe, don't forget that the Merc SS mid section already has 2" more setback than your 20" mid had. Ad this to the 10" plate and you're getting into an awful lot of setback on an STV in my opinion. I've gone from a 20" motor mounted directly to the transom to a 15" on 2 of my STV's and didn't like the resulting change in handling. My yellow boat has a champ housing which is 5" shorter than the 15", but still has the same extra 2" of setback built in. Incidentally, the 15" will go on your boat with a 5" plate and a little work. That's the way my red boat is now and also the red/yellow/orange one that I sold to Half Fast, but made the change before he bought it.

[Raceman]

There's one more thing you might consider: You can cut the rear of the boat where the mid will go on the transom with no plate, or use any size plate you desire. I'll look for a side shot of my Yellow boat which had this done at the factory. It's not a hard modification.

[Raceman]

I don't know if you can see enough detail here, but if it interests you I can find some better pictures or either shoot em and post em later in the week. This boat does have a plate on it because the champ mid is so short, but a 15" mid would bolt directly to the transom and doesn't require quite as much depth in the cut. A die grinder will make a smooth line without butchering gel coat the way a sabre saw would and then a piece of plywood is glassed in from the inside to seal the hole, with the area in the cut painted black. I've also seen another one at the races in the past with a snap on vinyl cover made to cover this area instead of doing any glass work.

[RUNWME]

Raceman

I would have to cut my transom alot to allow room for the hydraulic steering :(

This boat is a River Family Boat 1st and a drag boat second. I can't afford a second boat right now and my plan is to run the carb 2.5 3 weeks a month and then mount this engine 1 weekend per month to run Lake Racer.

Would having the engine set back that far slow me down for drag racing? I will be carry 1800 lbs of weight. Do you think it would be faster with 20 in mid mounted on 3 in plate or 15ss mid mounted on this 10 in plate?

Thanks for your help
David

[Hot Shot Merc]

I know your directing your questions to raceman but just whant to say that the set back on the stv hull will make your nose rase to high out of the hole.This boat was designed for a 20 inch mid bolted to the transom. The hull has set back built in allready.I run mine without any plate,right to the transom.And have gotten a better hole shot as a result..I hope this helps you.:)

[Casey]

everybody i know that races lake racer run 22p yamaha's and 1.87's. if your running 2 to 1's you will need a 23p. i have tried my 24p and 2 to 1's and it was to lazy out of the hole. 22p and 2 to 1's work great up till 1000' and then just stops pulling (98mph @ 10,300). i'm not sure about the set back, but you might want to email "Russ" or "W. Tripp" they both post here and know alot about setting up STV's for lake racer.

[Raceman]

"Would having the engine set back that far slow me down for drag racing? "

I think you'll have a lot more mid range porpoise with that much setback and I personally wouldn't run it. Of course when you're drag racin', handling issues do in fact slow you down more than if you were just looking for top end numbers at the lake. Again, the difference between the two with the 3" plate or the 9" plate is actually 9 inches because of the two extra inches in the SS mid itself. If I were doing all this switching you're talking about, I'd get the boat set up right with one mid or the other, then switch drop ons (complete power heads) back and forth, especially since you've got hydraulic steering to fool with.

[Firestarter]

That boat looks like a sprint bottom to me and not the later Mod-vp / ski bottoms. I could be wrong, as it is hard to tell from that picture.

RT

[RUNWME]

Picture of the bottom... Sprint?? Is this faster or slower then later bottoms?

I ran the boat with a 10 in plate when I first purchased it. It would porpoise if I was cruising below 40 mph and deliver a refreshing mist off the front sponsons. (haha)

The reason I took that plate off was because when slowing down and people in the back seat, water would get into the boat via the race hood scoup just behind the rear seat. With 3 in plate problem solved.

I couldnt tell any difference in MPH between the 2 plates, but did feel with the short plate it runs flatter.

No one has said the 15 in mid would be faster or slower then the 20 in mid. Only the jackplates may be slower. If that is the case, then most likely I will do as you guys suggest, run the 3 in plate with 20 in mid and switch only the powerheads when racing.

The proceeds from selling the 15 in offshore mid can go to race gas money!

I will find a 22 pitch prop and then set off for the course!

THank you guys for the advice!
David

[Raceman]

There's no way that there can be any speed difference between a 15 & 20 inch mid except for maybe getting the cowl down out of the wind. The advantage is better handling from lower center of gravity.

[Raceman]

If you're considering running the 20, why don't you try it bolted directly to the transom with NO setback plate? A lot of people prefer STV's in that configuration.

[Firestarter]

I am really mixed on the setback vs. no setback on the STV for drag racing, I have always felt that they come out of the hole faster without, but after watching Robbie Lamkin last year in Jasper, I am really mixed.
Really all I can sugest is test test test. It has been so long since I have fooled with the sprint bottom, I am not a lot of help, but I do remember them accelerating very well, but had a top end that was a little flighty compared to the newer bottoms. With weight, you may find you need the setbact to get it aired out fast enough, and the small diamiter of the yamaha won't help with the weight.

Good luck

RT

[RUNWME]

I used the setback plate for adjustability. I wasn't sure which hole to mount in so figured if I put it on a plate then I could easily adjust the height at the river.

The difference in the midsections are this. The 20 in mid has a land and sea 1 piece tuner on it (big holes for exhaust)

The 15 in mid has diamond marine drag tuner, is dry stacked and has offshore exhaust (comes out the back of engine)

With the cowling I have behind the back seat I would imagine aerodynamics would be much of a factor as it breaks the wind before the engine and center of gravity isnt an issue as you know how well these boats handle.


If I mount the 20 directly on the transom, which holes would you use? What engine height would be best combination between drag and river riding?

Thanx
David

[LARRY D]

i know for a fact that 2 of the top running lake racer boats are running 2.1 gears & 22 yamaha drag props.

[Casey]

i have always run 1.87's with a 22p, but over the winter i switched to 2 to 1's. i was going to swap back to 1.87's before the DSRA race next weekend, but i just ran out of time. the problem i'm having with the 2 to 1's is i can't get enough mph out of them. to win a lake racer class you need to be at or near 100mph. the most i can get is 98mph and thats at 10,300 rpm's.

[Raceman]

Casey, just out of curiosity, have you tried a 24 with the 2:1 gears? Playing with the prop calculator, it looks like the drop off in top end numbers with a 22 on a 2:1 gearcase compared to a 1.87 is much more severe than the additional speed the 24 would add on the 2:1. I can't see a whole lot more than 2 MPH addition with the 24 on the 2:1, where it looks like the 22 on the 2:1 falls off about 7 or so from the same blade on the 1.87. I realize there's a lot more to it than that, but it might be worth the experiment if you haven't done it already. Seems like those run em down on the high end wins always felt a little better somehow anyway.

[G-Train]

You better use the 15", because if your runnin Mod Pro rules, you can't use the Land & Sea Exh plate. onlt OEM stuff. The Diamond Tuner better be a Merc modified one also, or you'll be disqualifies if you place.

Casey,
How are the Mod motors doing against the SS motors with heads in Lake Racer???

G

[RUNWME]

OK.. testing time is what I need. This saturday I am going to test props and setups. 22 23 24 pitch drag props. I will try both midsections and setbacks and see which works best for this combination. I will change engine heights.

Without a better way to do this, I am going to hook a digital stop watch to my foot throttle. There are marker bouys approx 1/4 mile apart. When I idle to the first one I will stomp the throttle and start the timer, when I reach the second one, I will lift the throttle and stop the timer. With a GPS in the passenger seat, I am hoping to come up with relative numbers so I can track my progress through the day. I will run with tank full to try and keep weight consistant will top off after ever couple runs.

Any other recomendations on how to tune my setup? The boat flys flat and no handling issues, so hoping I get good consistant runs.


What are competitive numbers for Lake racer class?

THANKS AGIAN FOR ALL YOUR HELP!!
David

you guys have really given me good information to work from to save me HOURS during setup

[WATERWINGS]

David,

How do you expect ME to RUNWYE now????

Are you gonna use the bouys by the old sand bar?

[Casey]

Raceman, i have tested my 24p and 2 to 1's, but it just seems to be a little lazy coming out at 1800lbs (ODBA weight), but at 1700lbs (DSRA weight) they work great and that's what i run.

G-train, all the weights are pretty close in speed. i can't say that one is much faster then the other.

[RUNWME]

Waterwings... we have spent many miles riding beside one another without ever squaring off in a race. I kinda like to keep it like that.

There is one who I would love to square off agianst, whom said Joes Allison was a POS because he couldn't drive it and that my STV was a dog.

Anyway, I plan on having a race motor and a River motor. He may decide to jump on me one day and not realise that I had "forgotten" to pull the race motor off!

The Buoys I am referring to are a set on the Neuse river. Bruce is going to let me experiment with some of his props and buy the ones that works the best. I got one of those 3000psi trim pumps from him and will wire it 24v up 12 down.

[RUNWME]

Raceman will you be at Jasper race? I wont be racing in it, but would like to come check out your ride. I have never watched a OBDA race, and thought I might ride down there and check out the action. I found a guy who does fiberglass work who said he can do a sano job of shortening my transom.

Casey 22 pitch with 2.1 gears is 98 mph? I bet that thing launches like a banshee!

Since owning my STV, it has always sported a 28-32 cleaver 1.87 and performance out of the hole has been lackluster. When I put a 24 pitch yammie drag I thought wow! now this is fun!! 22 pitch, 300+ hp I can't wait to try that combination out of the gate! Weather permitting, Saturday will be the day.

[Casey]

ya it comes out pretty good for a 1800lb boat

[Raceman]

RunWme, I go to Jasper every year and have a room at the Acuff. I don't ever take a boat. I just use my old stuff for ridin' up and down the lake.

[WATERWINGS]

David,

The bouys by the old sandbar, are very, very close to 1/4 mile, (if the tides have not moved them since last year)

But you may not get very clean water saturday, (its the summer festival this weekend)

[RUNWME]

Waterwings
advantages of that sandbar is that its close to your house (and toolbox) for changes.
Disadvantage
I think everyone sitting at the sandbar will quickly tire of hearing this offshore exhaust indi car sounding engine romping back and forth in front of them at 9-10k rpms.

conclusion... check distance with GPS and hand out earplugs!

John, at the race in Plymouth August 9th they will be having top end speed runs as well. Will you be coming for that? I sent the intake from my 2.5 carb motor off yesterday to CHUCK GOODMAN. I will slap on a 32 wheel add nitrous and see what it runs. I am looking for 400hp ballpark hp with my river motor on giggle juice. I know I won't come close to top numbers, but I hope to lay down some decent numbers.

[Hot Shot Merc]

Hey man sounds like we got somethin in common.I'm new at drag racing too for the most part,i've raced a couple times in the last 3 years with my V-KING and like you have a drag motor on an stv.mines a copy though however they run the same set up it sounds like.I RU A 20 INCH OFFSHORE with 1.87:01 sportmaster witha 22 and a 24 yammy,mostly the 24 so far.It turns my 1650 lb.rig at 100 to 102 mph in the 1/4 @ 9500 r.p.m's.I just got my 22 back from Tillmans and have'nt try'd it yet but hope to in a couple of weeks after I break her in.I sent my 24 to him and should get it back soon as well.I use 24 volt trim on the floor for up only and have a 12 volt button on the wheel for fine tuning,I feel safer doing that.Tach and speedos with recall have helped me with my testing more than i can tell you also.I've run jack plates and ive run withoutand feel the 20 inch solid to the transom works best for me.The engine hight testing for me was easy.I started a little low and moved up one noch at a time till I found the right spot,the boat will porpus at 1/2 track if its too low.Bring it up till this goes away.Any way I liked to see this kind of exitement that it looks like you have.I had it too and still do.Be safe during your test sesion and try to allways have another boat there with you incase somthing happens.good luck and have fun:) :)

[Hot Shot Merc]

http://home.comcast.net/~hotshotmerc/boat14.jpg

[RUNWME]

Cool Picture Rob! Thanks for sharing your setup with me. Yes, the bug has bitten into me hard. Just a couple weeks ago I remember having money in my bank account and was perfectly contented thinking I had one of fastest boats in the area.
The I went to Plymouth and realized I had NOTHING!! Got
B%^ ch slapped and by the winner (even though I got runner up) and I started thinking.. hmmmmmm what to do what to do

I suppose I pouted a couple of hours when my wonderful wife answered that for me by asking me what I needed. Ofcourse my answer was A 300 DRAG MERC engine. That evening she agian proved to me that I was the luckiest man in the world when she said to pick one out, and that would be my birthday present from her.

[G-Train]

I'd like to propose to your wife.....

G

[RUNWME]

G-Train
Not that long ago, I tried to trade her for a 2.5 engine....

http://forums.screamandfly.com/forums/showthread.php?s=&threadid=34510&highlight=trade+corvette

None of the offers I got materialized and ended up losing my girlfriend in the process to Talon2.5

Alls well that ends well! I got to keep my wonderful wife AND get a drag engine!

David

[Raceman]

Seems like I remember offering 2 drag motors in trade and you saying somethin' about her not likin' old fat guys.

[RUNWME]

Yes you did Raceman! I think you were even offering 2 engines and some 2 stroke oil in the deal. I should have traded ya, got the motors and when you decided you couldnt keep up with her anymore, I would have had her back AND kept the 2 engines. lol
That would be very close to what Talon2.5 did to me over Terry.

Sheesh.. what was I thinking??

btw... I don't think I ever said she didn't like old fat guys. If so she would have kicked me to the curb when I broke 220lbs

[RUNWME]

OK, got it mounted and steering hooked up. Will install the fuel pump tonight and fire on the hose. Tomorrow start testing props, mids and setback. One change at a time.....

Another question though..what 2 stroke oil should I run and at what ratio?

Thanks
David

[RUNWME]

another... I am like a kid in the candy store!! I hope it puts down some respectable numbers tomorrow.

[Casey]

i think that most people will agree that Klotz R-50 is a very good oil and if you plan on racing it in the ODBA you have to use it anyway, so why not start now.

[RUNWME]

Do you mix same for drag racing as you do for River Ridding? I mix my other engines 40.1 not sure if I should go heavier or lighter on the oil when drag racing

[Raceman]

I like the Klotz also. Jay Smith likes the Pennzoil full synthetic and it's hard to argue with him as much as he's got his nose in powerheads.

I run my stuff at 32:1. I like the little extra protection and haven't ever seen any performance penalty for being a little heavier. Merc used to recommend 18:1 on the race stuff back in the dark ages.