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View Full Version : 24' Sonic w/twin 250 OMC Ocean Pro's



Instigator
10-23-2001, 10:07 AM
Kinda big for this site but still O/B.
Bought 3 1/2 years ago as a complete 1985 package.
Came with two R.H. rotation 200 HP Merc 2.4's.
I stripped to bare hull and re-rigged with two new '99 250 3 liter loopers on a new O/B transom bracket/platform.
The damn thing ran 80 MPH's out of the box, w/26" Choppers at 6400 RPM.
I was shocked at that good of performance and decided if I got that much that easy, I could "fine tune it" and see 90!!
NOT!
Everything I've done since then has either slowed it down or hurt handling!
Started with a bracket giving me 20" set back.
So I did the smart thing an added 6" set back (manual jack plates) and promptly lost 2 MPH's!
Also added Bobs nose cones over the winter since I was right at 80 MPH's which seems to be everybodies magic number for cones working.
Lost 3 MPH's and had to run almost full positive trim to get the bow in the air like before!!
The best one was being stupid enough to pull the air box and add Bob's exhaust snouts to open the exhaust ( I knew better) and frying a motor!!
Boat runs about 78 right now after dumping the plates and jetting up two sizes.
Will knock off the nose cones this winter and hopefully be back at 80 GPS next Spring and leave the damn thing alone!!
Not!
Over all, the boat is a blast to drive, does great in rough water, and is big enough to sleep two!

Flat Out
10-23-2001, 10:28 AM
Seen pictures of it and it looks great. I'm an OMC fan myself. I run a 95 Venom on my flat bottom J-Craft w/CMC ss lift for a total of 27 in. trans height. NO nose cone or low water pick up. At 6000+ w 28 Raker I still get 30 psi after 300+ hrs. With an OMC you only need a cone and lwp in the most extreme cases. OMCs pump way more water than Mercs and the stock cases are a couple of inches longer, so cones are not neccessary at 80 ish. I've been very happy with the big looper. Have thought about 225 carbs but it runs so well why mess with a good thing.
I hope you get your 80 back, some times they run great right out of the box.What props do you run, what oil and fuel. I've always used OMC oil and premium fuel as well as OMC HPF gear case oil.
Look forward to seeing your rig and meeting you and the S&F gang some time soon.

Instigator
10-23-2001, 10:56 AM
Yep, I did a bunch of testing last fall with the jack plates before I installed the cones.
Had the motors jacked to the moon before they ran out of water.
The wheels were slipping way before then anyhow.
I'm running OMC oil and crap gas right now.
When I rebuilt the scatterd motor this Spring it was killing me not messing with its inards!!
But when you use 90 gallons of gas at a time, 87 octane is pretty nice!!
The boat ran as good as it did out of the box due to the suggestions and advice I got from people at Sonic and then was lucky enough to hook up with a guy at one of the bracket manufactures who used to work at Sonic and was involved in testing the set back on the 24 O/B's !!.
He also told me that my hull used to be an old Donzi!!
I knew he was right because I then remeber seeing one for sale years earlier that was I think a '74 or 5 with twin small block Corvette motors and Volvo Duo Props.
That boat was Virgin!! Always kicked myself for not buying it!!
What part of Ontario are you in??
We were in Canadian water (Pelee Island) of Lake Erie last weekend.
We spend a lot of weekends at Leamington Ontario (by boat) also.
You should try to make next years "Rumble on the River".
Jeff Williamson and his broither Jamie both came down from Ontario this year.
Had several other Canadians planning ther trip but had conflicts come up at the last minute.
Jeff W. says he will have 2 or 3 other boat loads following him down next year.
http://www.essbasetools.com/rumble/index.html

Flat Out
10-23-2001, 11:30 AM
I'm north of Toronto. I know Jeff(good guy). Our club had our Muskoka poker run that weekend. Maybe we can schedule things different next year. Do you have a date set for 2002? Let us know as soon as its a go. You Americans would love some of our runs. The lakes are big, clean and not too crowded and your American money is worth 5X our Canadian and our beer is better.

Instigator
10-23-2001, 11:41 AM
Funny, Jeff said the same thing about our beer?
He brought me down a bottle of Canadian Club whiskey as a gift.
Took me 3 months to get the stones to attack it!!
Cracked it at a small party I had and that damn bottle made three of us sick that night!! LOL (yes, it was the whiskey's fault!)
Next years Rumble is looking to be first weekend in August.
Me and the little woman want to do a Canadian get away next summer too.
AnthonySS invited us to his this summer but we could'nt make it.
Last time I spoke to Jeff W. he said that he and the PBCC were planning an event for Mid July for next summer also.

Toffen
10-23-2001, 12:16 PM
Hi!

Did almost the same experience with my Phantom 25 & Promax 300.

1999:
Top speed 72 mph at 5.900 with a Raker 24. Setback 5.5 inches. CMC powerlift. Cruisespeed 48 mph at 4.000 rpms.

2000:
Bluprint of hull and rebalancing. Setback still 5.5 inches. Added Bobs Nose Cone. Top speed 75 mph at 6.000 rpms with a Raker 24. Best speed 76 mph with a Chopper II 26 inch at 6.000 rpms. However, gearfailure, and no warranty. Bought a Torquemaster lower unit, and top speed the same. No changes, only 200 more rpms. Experiment costs USD 4.000,-.... Cruisespeed at 50 mph at 4.000 rpms.

2001:
Added setback to total 12 inches. Top speed 78 mph / 67,8 knots with a stock Tempest 25 at 6.250 rpms. Top speed Chopper II 26 approx. 77 mph at 6.200 rpms. Still Torquemaster lower unit. Cruisespeed at 53 mph at 4.000 rpms.

Due to handling problems at high sea, back to 5.5 inches of setback. Top speed now 76 mph at 6.100 rpms with a Chopper II, and 76 mph with a Tempest 26 (blueprinted) at 6.000 rpms.

Added speedrails to give more bowlift. Should give 5% boost in speed. Total failure. Lost 3 mph... Top speed 73 mph at 5.800 rpms with Tempest 26....

Removed aft speedrails, speed now 75 mph at 5.900 rpms with Tempest 26. Front speedrails to be removed this winter.

Conclusion:
More setback on my hull = more speed, but to tail heavy at high seas despite bowtank. No more speed with Bobs Nosecone. Lost one gearunit due to adding nose cone on standard lowerunit. No warranty. Speedrails do not work. Bluprint of bottom and rebalancing hull (less weight in bow) a must.

Next year: adding 2# spacer to total 7,5 inches. A compromize between speed and handling. Watersand and blueprint bottom again. Will test out a blueprinted Trophy 25, although I feel the Chopper II and Tempest will be faster still. More proptests.

For serious speed, buying another boat as well: Skater 24 with twin Promax 2.5 offshores = 118 - 122 mph ... Phantom for offshore racing and cruising.

Cheers and good luck, Toffen - Norway

Instigator
10-23-2001, 12:35 PM
How yah doin??
Yours is the first real experience I've seen on the speed rails.
Remember looking at them when they first came out, years ago.
Looks like they should work??
Kinda like set back and nose cones I guess.
Wow, big jump to the cat huh?
When do you get it??
Good luck

Toffen
10-23-2001, 02:45 PM
Hi!

The 12 inch setback did work, however, the boat was a handful to drive in high seas depsite a trimtank in front. So, I expect to gain 0,5-1,0 mph with 2 inches more (total 7,5). With 12 inches the boat looked like a Fountain, the transom almost under water!

I was suprised also that the speedrails did not work. I tried with borth 4 and 2. It seem to me that they lock the bottom to the water. Difficult to free the hull.

The previous owner of my Phantom had Johnson V8 4 litre mounted direct on the transom. The shaft was 20 inch on a 25 inch transom. So they had in fact 5 inch lift. I used approx. 400 meters to get on plane, but the boat ran a honest 75 mph with a Raker 22! With 5.5 inches of setback, the total weight with my Promax 300 should approx. be the same as with the old giant.

According to Phantom in UK, they do not like setback at all. They reccommend to mount the engine direct on the transom with a 20 inch shaft. I have not tried it with my Promax 300. Maybe I should?

I am working on a project including a Skater 24 and twin 2.5's. Each engine has dynoed in excess of 300 HP. The engines are ok, but we are still waiting for a confirmation for the Skater. A friend of mine is a vital part of this. He is a professional F1, F2 and Offshore racer (Skater 28 w/twin 2.5's), and he is organizing the engines and boat.

Our plan is to set the world record from Norway to Denmark return in 2002. The record is 21 years old. Average speed is only 51 knots, but the area is really offshore. So you need to pick the right day and time. Start off early in the morning, and call the press when we have done it. Too many tried already, and too many television teams involved!

I would prefer a 28 Skater, but if the Skater 24 is what we can get for a reasonable price. Thats will be it. I will keep you updated. Great service from DouglasMarine. Got rigging advice in no time.

Cheers, Toffen G

Instigator
11-02-2001, 11:07 AM
Are you serious about your Norway to Denmark record attempt??
If so, tell me about it.
How far, what kind of water conditions etc???
If its ruff, open water are you sure you want to do it in a cat??
I'll let you borrow a Vee Bottom, if you pay shipping!! (course it comes with the driver) ;)

Toffen
11-02-2001, 01:00 PM
Hi!

The distance from Tvedestrand in Norway to Hirtshals in Denmark is approx. 70 nautical miles. The UIM record is Norway - Denmark - Norway. The distance is really OFFSHORE, and if you are unlucky the waves can be nasty 30-40 feet in the wintertime.

However, I know several people who are travelling over in their 20-25 feet boats during summertime. To be able to hold fast enough speed it has to be flat water. Sometimes during the spring and late summer, the weather conditions are perfect. No wind for several days, and no rollers whatsoever.

Many people have tried to beat the 21 years record, but they have been very PR orientated, waiting for the press and media to come, before starting off. Bad idea. Normally the wind blows up around 1100 in the morning, and then you have to be back home celebrating with a pint of beer!

The sun rise in the summer approx. 0230. Then you have to be ready. If you have a average speed of 70-80 mph, you will be in Denmark within one hour. You have one hour pit stop for fuel and service. Then its back home!

20 years ago they staged one of the roughest offshore worldchampionships in Tvedestrand. Tvedestrand is some few miles away from Arendal where they stage Offshore Class One (Victory Team, Spirit Of Norway, etc). The old races were Norway - Denmark - Norway, not those inshore "offshore" races they do now. So you looked at the 20 boats leaving, and waited some hours, and there(!) one - three came home in one piece!

The attempt to beat the UIM record is very low key. We will call the press when we have 30 mins left to be inshore back home. Frode is a professional offshore (Skater 28 w/twin 2.5's) and Formula 1 driver, and mad (and skilled) enough to do it! Then its up to me to be tough enough to steer the rig....

I will keep you guys updated.

Cheers, Toffen

PS! How close do you have your Johnson Rudes? I may mount twin Promax 300 on my Phantom 25, but they have to be only 20 inches from eachother centerline to cenerline. How will this affect propbite (if any) ?

Instigator
11-02-2001, 02:40 PM
I agree on the inshore/offshore racing over here.
Pretty much a joke in my opinion!!
When they race in rivers and it call it offshore---something's wrong!
I like reading about the old days with Don Arronow, Bob Magoon, etc, etc.
When men were men and sheep were nervous. ;)
Your record run sounds fantastic.
Also sounds like you have done your home work.
A couple of hour time window looks to be the whole key!!
We got weather'd in on an Island in Lake erie last summer for three days waiting on the 8' waves to subside.
We finally realized that first thing in the morning there was about an 1 1/2 hr time window of smoooth water before it kicked up again.
There were 4 boat loads of us and two of them got anxious and decided to risk the 45 mile trip home.
We watched as the first boat (26' crusiser) got stood on end by the first wave they hit and continued to get pounded until they found refuge in the harbor of an island 15 miles into their trip.
We (2 boats) set our alarms for 6:00 A.M. and tied everything down the night before to be ready to leave the next morning.
Just as expected the lake was flat as a table top and we ran 65 MPH's for the 45 miles until we caught the two boats that had left the night before and had ther **** pounded out of them!!
Anyhow, my motors are 24" apart.
I think the old 2.4 Mercs were 22".
Closer together the deeper you can run them and still float the bow ( and lift the boat) w/o pulling the wheels out of the water.
If you mount them too far apart, as the boat lifts at speed, the props raise too high and lose their bite.
The negative is, the closer together they are, the more squirely the driving/handling of the boat.
You can't take your eyes off of the water for a second in my boat at speed w/o paying for it!!
Good luck, take lots of pictures and keep us posted!!
Instigator