292 SR-1 Shorties and Extension Boxes
 

I'm starting this post to inform 292/311 owners the benefits of short drives and Merc extension boxes. I've been searching for years on the benefits of short lowers on the 292 or 311 and have come up with nothing. This spring I'm installing new Bravo uppers and Sport Master -2 lowers my 292 SR-1. In addition to that I'm also replacing the standard gimbles with new Mercury Racing ITS transoms.

Up till now I've been running HP450 engines with the old school blunt nose bravo drives. With that combination I was able to hit 70 mph (gps) with Bravo 25 pitch props that were labbed at Mercury. 5200 RPM's was my max RPM which puts me right around 12% slip, which is respectable for this hull.

So over the next few months I'll be installing everything and then I'll report back.

You ever boat at loto?

Very interested in your results. Good luck!

I'm curious also

No- my boat is kept in Northern Michigan, as is the vehicle I tow it with, so it's pretty much stuck there. Which isn't a bad thing, Northern Lake Michigan is a great place to boat.

If ya got a trailer and a tow vehicle you can come to the ozarks...

Sounds like one of my projects. HAVE FUN

I just booked my slips for the 4th in Traverse City and Boyne Thunder. You going to either of those this year?

Update when you get it to your project

I won't be at Boyne Thunder, but I may go up to TC. I keep my boat in Portage Lake in Onekama. If I come up for the week, I my trailer the boat up, I'll let you know if I do.

I've got the boxes, and I'm hoping to pull my motors and gimbles tomorrow. Mr. Gadgets is currently building one of my uppers. Everything is moving along.

So are you putting the boxes and shorties on at the same time? It would give you more data to do one at a time, but that may involve more work I am not too familiar with the process of installing boxes.

It would seem that with the setback plus the extension boxes, they will cancel each other out and you may end up at the same relative prop shaft height?

Yes this is all getting done at the same time. Time is limited and this project is a fair amount of work. Ideally it would be nice to test each thing out and see what the results are, but unfortunately I don't have the time to do that. Plus my uppers are not built yet, so that would push me back even further. I did install the boxes on today and it really is a nice set up.

As for the boxes canceling out the shorty's, the gimbles appear to be the same height as they were prior. Merc has the Gimble mounted around 1 to 1 1/4" higher than the mounting location of the stock location. Once mounted, due to the transom angle they are at the same height. Also remember these are only 7" deep. From what I've read with a 12" box you add 1" of prop shaft depth, so with 7" I should lose around 5/8" of effective prop height.

Here is a picture of the standard gimble and the ITS gimble. You can see that he ITS raises the position back to the stock location, possibly slightly higher.

Very interested is the results. I've been thinking about shorties myself.

Got any sound bytes of your boat running with the drilled box?
What motors you have again?

I'm running modified 420's. They are basically HP 450's now with 741 cams. I'm running dry to the tip Gil manifolds and without the platform on they're loud, if I remember right 91 db's at idle with one engine running. With the drilled platform it's quieter, but I forget how much; however it quite a bit louder than with he silent thunder complete.

It would have been nice to have done testing with each step of the project but with limited time it just isn't possible. If anyone is thinking about external steering- look for an ITS setup. Yes they're expensive but it fits perfectly, and best of all you don't have to modify a thing. Soon we will see if there are any speed gains- for my sake I sure hope there is.

So, the Merc extension boxes raise the gimbal 1", then the shorties raise the prop shaft another 2.5" for a total raising of the prop shaft of 3.5"?
Then the setback is the equivalent of lowering the prop shaft 5/8" lower?

No- The ITS box mounts the gimble about 1" higher. Once mounted to the boat, it appears to be in the same position. I'm sure this is due to my transom angle. I don't have any drives to mount up right now so it's really hard to tell exactly where things are. The shorties are 2" less. My propshafts should be at 5" below the transom, they started at 7" below. Once I get the outdrives on, I can remeasure and see where I ended up.

The 5/8" loss will come due to the water coming up from under the hull. That is all theoretical though. When all is said and done I should gain 2" of height to my prop shafts.

Should have bought the 5 inch extension box for the ITS drive and then use the long IMCO input shaft. Gets you all o]the benefits of a 12' box. That boat could probably use it.

They make a 5" box that extends them more? I've not seen these.

I saw them advertised somewhere in the last 6 months. OFFshore, Boatfreaks or Riverdaves.
I would look into it. That boat is a tank and could use the bow lift add.
Almost bought a 35 Formula the year before I bought the 34 Scarab.
Formula = Gentleman's Offshore. What I was always told.

My boats not that heavy- 7000 lbs. Here are some similar sized boats that what they weigh

2016 Baja 30 7775 lbs
2000 Fountain Fever 32 ( same size as my 292) 7400 lbs
2000 Cigarette Mystique 7800 lbs
1999 Cigarette Bullet 8600 lbs
2015 Sunsation SSR 32 7200 lbs
1988 Scarab Panther 30 6400 lbs

I know lot of people like to say Formula's are tanks but it just isn't so. Fountain's may appear lighter but its all marketing. A 32 foot Fountain would be lucky to be as large as my 292 when you take the swim platform and the beak off that measurement. When you include the swim platform on the 292 it's actually a 31 foot boat. Boats like Fountain add pads that do make them faster, but then you lose rough water handling. Fountain also uses really high x dimensions, which certainly make them faster. Everything is a trade off, however as you can see my boat is actually lighter than most other boats in the same size range. Even the 357 isn't really a tank compared to other boats it's size, 8500 lbs (for a 35'7" or 37'7" with platform boat) isn't bad at all. A 35 Cafe' Racer comes in at 9400 lbs.

It's not all gained from just raising the prop shaft 2"...you gain a lot by moving the props into cleaner less turblent water..and weight distribution moving the drives back further..

I agree completely. The 311 came in two ways- bravos and trs. Everyone likes the way the TRS boat handles and rides better than the Bravo- The only real difference is that the engines in the TRS are mounted forward more, hence changing the balance of the boat. I'm hoping that while completely different- adding the boxes archives similar results.

I am curious to see how far back the propshaft will be. Mine was 32 5/8 with the KAAMA. I agree that with the engines being forward it did help the balance however it hurt me not having the drive in the water for bow lift. I would believe you should have a TON of bow lift bringing the drive back.

What kinds of wheels are you planning to run?

I have been running Bravo 25 pitch props labbed by Merc. I've got a set of 30 pitch Bravos, repitched to 27 and have had a lot of work done to them. They were originally labbed for a 28 Pantera. They are at B-Blades right now getting tuned up. I'm not sure if I can turn them or not with this set up, but I'll run them and find out. If not, I'll store them until the next stage, which is going to be a set of 300 AFR oval ports, but that is at least a year out.

We put 2in shorter drives on a 1990 311 a about 10 years ago and the it made a huge difference in the boat. It ran flatter, went faster, and handled better. We have also put Boxes on few 41 Apache's ( none step bottom ) boats and it also really improved them. I have boxes on my 382 Fastech and feel that they really complement that hull. I think one of the biggest reasons a stepped bottom is faster is that is when they started with the higher X. If I were you I would try the shorties first because it is so much easier and a lot cheaper but if you go with Stelling Boxes they can be adjusted up or down and you might not need the shorties. When you are looking into your cost don't forget you will need new props, and it would be a good idea to up grade your steering. Sorry I can't give you a better answer on the best way to go if you pick one or the other but each one or both will make a big improvement on your boat. If you would like you can PM me or call at 616 566 2679 and I will be more than happy to help you anyway I can. Rick

Stellings will but you back 12 ins. As far as bow lift with the higher X you will run flatter. If it runs to flat you can turn your props in and pick the bow up a little

That is where I was going with asking about the props. I turned mine in. I believe endeavour's boat will want 5 blades after these changes

Wouldn't 5 blades give me even more stern lift? I've always thought that boats that run 5 blades need them for getting up on plane.

Kevlar- I've already got the boxes installed, and all of my standard length lowers are gone. I'm putting a lot of faith into the fact that this setup is going to work.

Yup with the changes you are making the boat I am guessing it is going to want that. That is just a guess based on my 311 experience granted I had surface drives BUT your moving you drives up and back as well.

5 blades should also let you trim up more. I am excited to see you do this on a 292 I love to see old birds get faster!!!!!!:nicethread:

I think you will be really happy with the out come. Very cool project. The 311's and 292's are such nice boats, some of the nice riding boats out there for there size.

Kevlar- Have you ever brought your boat up to Portage Point Inn in Onekama? There used to be a guy that would come up from Holland in a Fastech. I'm curious is that was you? I thought that boat was a 353 but it could have been a 382.

No not mine. I'm not sure where that is but my boat has never been out of the great lakes. It has a one off paint job, one of these days I will post it in the pics of Formula's. I have been meaning to for a long time.

Any news?

Not yet- It's been cold here the past few weeks and I won't be back in Michigan to work on the boat until April 23ed.

Ya keep the boat that far from you??

Yes- I don't like boating in Chicago, and I like the harbor system here even less.

Any news on this endeavor?

I know you bought Steve's motors too are you going to run it first then do the swap?