Lightened Flywheel - raised limiter RESULTS!!!

[David Lanham]

Yes, a slight cross wind caused my nose to drop once while running in light chop near 94 MPH. I knew when it dropped that I was on the ragged edge of blowing out. I ever so gently pulled back the throttle and hit the down trim without incident.

This actually happened at one of the Rally

 

[aaronmt]

This last summer we were camped 15miles down river on the Columbia river from where the party was at. Mid way through the day I had to run back to Ghettys Cove to check on my dog(Potty him,change his movie,check the ac in the camper):embarassed, hes teh only kid we have so far. When running 15 miles down and 15 miles back I learned and incredible amount about the hulls. The wind on the Columbia can go from 0 to 50mph gust instantly when you round a corner. It was nerving at first to feel the back sliding all over from the sparatic gust,but once you got used to how it reacted it wasnt that bad. I was running anywhere from 70-85mph in these conditions.There is no way in the world the gf would of wanted to been in it like that though. I will be sending my computer/flywheel out in a few weeks, I to am more intrested in the acceleration then the big top end number. Im very glad to here your boy is ok, we did a bat turn this summer running 80ish with 4 people and that was no fun for sure.Hard to convince her and even the buddies we need to go faster after that.Aaron

 

[Scott in MN]

Had a buddy run a 28 ET once and he came by all out of shape. After a couple of runs he took it off and went back to his "Texas" cut chopper. Said he couldn't keep the ET under the boat...boat was an xb2002 and he could drive.

 

[2fast4mom]

Great numbers Bob and a great read!! Glad your son is OK, bat-turns at 90+ can be real ugly!

 

[catfish123]

Thanks Lou.............it was amazing how flat the boat stayed during all this..........has to make one wonder with a 3 liter motor if all would have turned out the same.

 

[K-DAWG XB 2003]

Man here we go again with the hookin talk. That scares the livin chit out of me. I havent and as far as I know havent ever been close to hookin, bat turnin or anything like that. As far as I can tell from the board I am the only Ally driver on planet earth that hasnt. I was told by some I think it was Ted (2fast2Pass) that if I start chasin the topend speed it was only a matter of time before I went around. Glad your boy is OK.

 

[catfish123]

I believe in the quest for a high top end number, it's easy to sort of forget or lose sight of what you are really doing. A bat turn like this at a pretty high speed helps to renew the respect all this deserves..........of course after a change of underwear.................LOL

 

[froggy]

When I had the limiter, on my 280, changed to 8600, I requested that all the sensors remain operational. The one that seems to protect me the most is the low water pressure sensor.

I can run a certain prop 1.25" above the split and all is well and change to a transom lifting prop and have to lower the engine as much as 1.25" just to keep water pressure so the engine will rev.

The point I'm making is that sometimes different props need radical changes in propshaft height to remain safe.

froggy

 

[badbait]

Froggy, thats a good point. I like many of you have been testing the upper limits of my Allison for a couple of years. After rereading your first post I noticed that you folks made two changes before your last run. First you took off the Trolling Motor and second you changed props. Was the boat rebalanced side to side after taking off the troller. If not this would cause the boat to be harder to drive after getting up to speed. If out of balance enough it may cause it to drop over on the right after Matt got through the acceleration portion of the run. It's always better if we can learn from these types of accidents. As someone mentioned above top end runs are never completely safe.

 

[GFinch]

How can you check to see if the trim bushings are bad? Thanks.

I have an OMCease, I grab the lower unit and push and pull it from side to side and then away from the boat, noting excess movement.

 

[catfish123]

We did not rebalance the boat after taking the trolling motor off. The 30 Chopper II seemed to run fine the way it was so we put on the 30 Lightning. We have never put a level on the back of the boat at rest, etc. We go more by the way it looks with regard to being level when we run it. Some props seem to make it lean a little more to the right than others at higher speeds which is why putting a level on it at rest was never something we did. Are we wrong in this? Just looking to learn and stay safe. Bob

 

[hack02]

" Sportmaster case with some modifications."
What type of mods were done to the gearcase? Just thinking out loud, searching for clues.

 

[catfish123]

Skeg modified to 200 profile, nose blunted somewhat, port side of skeg sanded to match up with curvature of starboard side at the torque tab, one water pick-up welded shut, etc. This set-up has run many, many times over 90 mph with no problems at all so I'm doubtful that the gearcase mods contributed in any way to the problem but I do appreciate all the input I can get. Thanks, Bob

 

[Darth VMAX]

KDAWG,

I don't like the hookin talk either, and I have never hooked mine. That was one of my justifications for the TRP Lower Unit. Safety with my family. Not sure it would actually help any but I have never hooked or even been close to hooking. Course I havent run 90+ mph either. That may change since I just added more Hydro-Tec HP ;-) The TRP's are slower for sure, but I like them so far.

Catfish, your 225x sounds like one bad mofo! Glad you are happy with the results

 

[froggy]

Catfish,

As BadBait said, it's best to reset a number of things when one changes a prop, changes an engine height, changes the load, etc.

I go out and trim hard at about 50 mph and note where the boat propwalks (transom starts moving abruptly to the right) on my Stainless trim gauge. I repeat this event three times to be certain, then I stay trimmed under the, event producing, height when running for top speed. I do this EVERY TIME I change engine height, prop, and load.

Since I run props, for a prop builder, i have quite a bit of time running for top speed. One of the things I've noticed is that I have to run an ET prop lower than a Chopper II prop. The Chopper II can be run higher than most props and still hold the nose up.

I hope this helps.

froggy

 

[catfish123]

I agree 100% Froggy with your evaluation of engine height for an ET vs. Chopper II. Every number on my Detwiler exact dial equals roughly 3/8" in movement. We have run the 30 ET many times at a setting of 10 1/2 at speeds over 90. The other day when it blew out, it was at 10. The 30 Chopper II is normally run at 10 1/2 and 11 would probably also be OK. In order to get the rpm's up, the Chopper II must be pretty high. Again, both Matt and I have found the same thing you are saying between the two props to be true. We do not run very often without the trolling motor. Hardly ever. I don't know if having it off was the contributing factor or not but maybe it was. There was some chop on the water with a cross wind. Maybe that contributed? There were some leaves in the water. Maybe those interupted the flow of water for a second to the prop? We'll probably never know for sure but I do appreciate everyone's input.

 

[fishnfireman]

Great thread guys-----

Parts of this would make for a great book or at least a sticky.

 

[fishnfireman]

Catfish,

As BadBait said, it's best to reset a number of things when one changes a prop, changes an engine height, changes the load, etc.

I go out and trim hard at about 50 mph and note where the boat propwalks (transom starts moving abruptly to the right) on my Stainless trim gauge. I repeat this event three times to be certain, then I stay trimmed under the, event producing, height when running for top speed. I do this EVERY TIME I change engine height, prop, and load.

Since I run props, for a prop builder, i have quite a bit of time running for top speed. One of the things I've noticed is that I have to run an ET prop lower than a Chopper II prop. The Chopper II can be run higher than most props and still hold the nose up.

I hope this helps.

froggy

John,

Do you have a rule of thumb. When it comes to starting propshft hieght.

Like a heavy load vs light load.?
Over hub vs thru hub ?
3 blade vs 4 blade ?
Cleaver vs full ear ?

 

[badbait]

We all need to learn if we can from your sons experience. I have a lot of time running on the top end with and without the troller on. My experience has been that I have to add at least 20 lbs (depending on the prop) to the far left compartment usually inline with the drivers seat or at the backend of the rod locker on my 2003 when I take off the trolling motor. Being out of balance really shows up on the top end after the acceleration slows down. While acccelerating the prop is helping to keep the right side up. I really doubt that I could drive my boat to it limits without it being close to perfectly balanced. I'm sure it would be a real handful especially if your prop is giving you some tail lift. I hope this doesn't jinxs me but I to have never done a bat turn and at 67 years old I really don't want to. I have done a 180 when my lower unit siezed up at about 93 miles per hour but it came around gracefully and kept me in the seat. When the lower unit siezed the prop became the rudder and it took me around. Hopefully that is as close to a bat turn as I will get. After making changes like the ones you folks made I think it's important to not just get in the boat and take it to it's limits. I take it up slowly and make weight and seat adjustments by sliding my seat one way or the other and then go through that routine again until I'm satisfied it's balanced. It's also very important to know exactly where your motor is trim wise especially if your running high propshaft heights. If your setup is right you shouldn't have to go much past neutral trim if any at all. My fastest speeds are obtained with a little bit of negative trim.

 

[catfish123]

We, for solo runs, have a 25 lb bag of shot that we normally put in the far left side compartment directly across from the driver. We only have side steer set-up. Matt actually put the bag in the very rear of the boat in the left, back compartment the other day. Yeah, I know, yet another variable. I'm thinking maybe with the troller off, he may have been trimmed a whisker too high since it wouldn't have required as much trim to theoretically keep the nose up without all that weight out there???