Small diameter gearcase options - selection

[Mr.Rude]

I am looking for a small bullet diameter case for a 60 degree OMC looper project. I am fabbing my own mid and have not decided on a gearcase pattern for it yet. I am debating between an OMC V4 lower or a Merc XR6 case. I would like the 1.87 gears that the Merc offers best. Does anyone know the hp limits of each case? Does anyone know if the newer style OMC works well with a LWP in higher speed applications. Will be on a light F2 hull and wanted a shiftable case.

[patchesII]

Remember the fastest Mercury powered dragboats run XR6 cases so they can handle a bunch of power

[Mr.Rude]

Good deal, thats what I will do. Big props are rare for a V4 to get top end speed. It will be used for a drag type setup and not for every ounce of speed. I should be around 200hp so I wont be doing to much to hurt it then:)

[MercNuts]

Remember the fastest Mercury powered dragboats run XR6 cases so they can handle a bunch of power

It is also worth considering that the high horsepower drag boats that run XR6s have versions with upgrades for strength and durability. David Steckbauer in Wisconsin is the master of the XR6 upgrade. Also I think XR6 cases have 1.78 gears instead of the 1.87s in the larger cases.

In stock form the XR6 is probably stil stronger than the V4 OMC case.

[Mr.Rude]

1.78 = even better!

[patchesII]

It is also worth considering that the high horsepower drag boats that run XR6s have versions with upgrades for strength and durability. David Steckbauer in Wisconsin is the master of the XR6 upgrade. Also I think XR6 cases have 1.78 gears instead of the 1.87s in the larger cases.

In stock form the XR6 is probably stil stronger than the V4 OMC case.

Yes, most do but not all. Many of the Unlimited boats ran 1.78 cases, which means stock internals. My biggest concern with an XR6 is the skeg on real high transom heights on a tunnel

[johnboy 88 vegas]

If your gonna be racing it just stick with the V-4 gearcase and save yourself the hassle of changing the shift linkage around. If realiability is what your after...(riding 30 miles up or down the river with no one to pull ya back) then maybe think of the Merc case. Either way its gonna be a guess as to when either will puke in stock form.

[donmac]

so who has the upgrade knowledge for the case! I just picked up a mint xr6 lower for my vking and bolting it up to a modded,carb v6

[patchesII]

It's not cheap if you go with Sportmaster internals. Expect to spend 2500 more after you have the case. That's if you can find a Sportmaster propshaft. If you're good with the 1.78 gears Steckbauer makes a billet carrier for an XR6 propshaft. Won't be as strong as the hi perf internals but still not too bad if you're careful with it and maintain it

[donmac]

where do they usually fail?everybody keeps talking "pinning the carrier"! the load is on the forward gear! I can see a billet carrier with a bigger bearing keeping the shaft stable while surfacing,but don't see what advantage pinning the stock carrier does unless it was a lefty conversion!

[patchesII]

Pinion gear is the biggest weak link

[Capt.Insane-o]

Stecks carrier is absolutely essential, as is NEVER shifting with the motor running or a hard unload/load from such as a wave jump. A perfect set up just to the tight side of specs. I run a expansion bottle as well when running one. They will live fair enough spinning a smaller prop 24-28 high rpms, but trying to turn a 30-34 is a quick certain death. The skinny little thin skeg still scares the **** out of me on a v hull though.

[rev.ronnie]

Capt.
In your opinion, what is the breaking point most common; at the hit of the throttle to mid-range breaking gears or top end load and side load on the Propshaft?
I would guess that mort carrier problems are associated with side load and heat combined, letting things get spun out.

[johnboy 88 vegas]

If Mr Rude's hp goal really is 200hp then there is really no reason to do anything to either case. Extremely high prop heights are gonna take their toll eventually but a 1/4 mile at a time will take a long time to wear either out. Like Capt Insano just said the thin skeg would make me think twice if your running a v-hull that has a bad tendency to hook if the bow drops or heaven forbid something actually breaks. Since your running a F2 hull it might not be as much of a problem...just hope the prop free spools and don't lock up at the buck 10 if something internally happens.

[Capt.Insane-o]

Capt.
In your opinion, what is the breaking point most common; at the hit of the throttle to mid-range breaking gears or top end load and side load on the Propshaft?
I would guess that mort carrier problems are associated with side load and heat combined, letting things get spun out.


I always broke the stock carrier and or damaged the reverse gear thrust surface/"bearing" (there is not bearing for the reverse gear, it just rides in the carrier). Never had too much problem with the gears, smooth with the throttle on and off and avoid hard throttle chops, even under my drag motor they survived well enough with moderate lake use. Love the way they handle though, they are the cats ass on a viper. Except for the impending doom feeling knowing the skeg is very marginal in strength.

Any stock fishing carrier is completly inadequate for surfacing use, that litttle weenie needle bearing in the carrier is not made for that kind of use, you can pin carriers all you want, but it will fail eventually. I bought one of Steckbauers carriers second hand and it's been great. I made one of my own as well and have had no problems with that either.

Running on an F2 boat with 200 hp it'll be fine, but I'd for sure update the carrier.

[donmac]

thanks for the tips! I'll do a little more research! where is this "stechs" located!

[Mr.Rude]

It s going under a 60* OMC block so the power is limited by design anyhow. Just looking to have fun with it and get something going.

[Forkin' Crazy]

Good deal, thats what I will do. Big props are rare for a V4 to get top end speed. It will be used for a drag type setup and not for every ounce of speed. I should be around 200hp so I wont be doing to much to hurt it then:)

I've seen a V6 propshaft turned down to fit in the V4 case.

[Mr.Rude]

Yeah Forkin, I have heard of that too, as well as just having an IM of one for sale. I debated the same thing but it just added to the overall cost. Right now, I am just looking to get on the water, but will likely change up to something different as my need for speed increases.

[Mr. Demeanor]

Could the small V4 Yamaha gearcase be adapted? Then all the small shaft Merc props would fit. Mine has held up pretty well to being surfaced and my engine is really high. Gear ration is 2:1 though. I dont know about the gears but the bearings are the same as the V6 Yamaha lower units.

[Mr.Rude]

I do not know anything about a Yamaha lower so we will have to see if anyone chimes in...

[Freddie Webb]

I have a v4 crossflow gearcase with a stock 1977 v6 crossflow propshaft in it. My friend and I put it together and never had a problem with it. I even put it under a modded looper v4 with a 125hp shot of nitrous. If it grenaded tomorrow it has been a great one. The reverse gear from the v6 crossflow is turned down and the teeth are turned until the surface is smooth. So you will only have neutral and forward. I will look and see if I have another laying around to show you what I am talking about. It is not as hard as everyone makes it out to be. If I can do it anyone can.

[terry taylor]

I have a v4 crossflow gearcase with a stock 1977 v6 crossflow propshaft in it. My friend and I put it together and never had a problem with it. I even put it under a modded looper v4 with a 125hp shot of nitrous. If it grenaded tomorrow it has been a great one. The reverse gear from the v6 crossflow is turned down and the teeth are turned until the surface is smooth. So you will only have neutral and forward. I will look and see if I have another laying around to show you what I am talking about. It is not as hard as everyone makes it out to be. If I can do it anyone can.---------------------Is everyone making it out to be hard
:)

[Freddie Webb]

I didn't mean it like that. I was just trying to help. I was just sharing my past.

[terry taylor]

I didn't mean it like that. I was just trying to help. I was just sharing my past.------------------------------------------Just a couple of old friends :cheers:kidding around

[Capt.Insane-o]

The 1:78 ratio of the xr6 is hard to deny though :)

[Freddie Webb]

The v4 crossflow only came in 2:1 and 1.92:1 that I am aware of. Wilbur Weeks ran a 1.92:1 with a 28 pitch mercury offshore prop tweaked by Mr. Britt Platt. The mercury xr6 would definately give you more gear options.