Run Allison Transmission oil pump with engine off

[sailorryan]

There are no significant advantages to single engine operation, but the idea of a cable or electrically operated brake is exactly what I was thinking. Electrically operated could be tied in to the engine in such a way that the brake would automatically disengage when the engine is running, making it relatively mistake-proof.

But again, since there is no real benefit to it, just run both engines. If you're still bent on making it a trawler search for Brian's thread on over-propping for slow speed operation.

There are advantages in that you can load the single engine up more. We do 7.5 @ 900-1000. We can also control maintenance easier as both engines do not wear exactly the same. Previous owners did hull mods among other things and trying go much faster spikes fuel for not much gain in speed. I am mostly concerned with wetstacking, and if we were to run on 1, it makes much more sense from an aero standpoint to free wheel then lock the 4 blade fixed down.

Over propping is an option of course, but for the confines of this thought experiment is outside the scope. It is much easier and less costly to just hook up an oil transfer pump.

[sailorryan]

Why is it that you're unwilling to share why you need to free wheel the gear with the Sam's community?

And look where we went... =) Off topic, people saying its stupid to do things differently then the do, buckets of geniuses lol

[Boatsb]

Then Bobk running 3k miles a year at hull speed I'd doing it wrong?

Bob has probably put more time on his engines year after year than anyone else I can think of.

If you think you know better have at it. The idea of running one at a time still keeps the engines at similar hours if you switch between equally. Also the hours on both engines running easier will wear them less. Every argument you raise for making the modification can easily be shown as flawed.

If the boat is such a gem why mess with it? It's lasted how long already?

[sailorryan]

Then Bobk running 3k miles a year at hull speed I'd doing it wrong?

Bob has probably put more time on his engines year after year than anyone else I can think of.

If you think you know better have at it. The idea of running one at a time still keeps the engines at similar hours if you switch between equally. Also the hours on both engines running easier will wear them less. Every argument you raise for making the modification can easily be shown as flawed.

If the boat is such a gem why mess with it? It's lasted how long already?

You and Bob are NOT doing it wrong. You are doing whats right for you, your boat, your setup, your equipment, your priorities, your local waters, your environment, your goals, your time, your wallet . There just is usually more than 1 "right way" especially when you change all those variables.

I have discussed the pros/cons of removing a prop, changing injectors, running low rpms, shaft locking elsewhere and I just wanted to exclude that for this post. Everyone usually starts there and I wanted to see if there was some outside the box thinking that was an alternate. After I have figured out all the options, then I go and compare based on my variables and make a decision. I wanted to make sure I exhausted all options before moving forward with something.

A couple of PMs and a call with Acadian gave me 1 last option to weigh.

Why mess with it? Simple. Previous owners had different priorities then us. For example, they were retired and would relax underway. We are in our 30s, and work from home frequently. We like to do 6,7,8 knts because usually we are working while on auto while trying to simultaneously manage the kiddos (previous owner's kids were grown) and slower is safer for us while we multitask and more enjoyable.

We like being out on the water as opposed to being at the marina or on the hook, slower increases our time tooling around checking things out. Coming from sailing, being able to go 7knts in a straight line 24/7 regardless of wind is fantastic. If my baseline was a jet boat, I would probably be bored out of my mind. If someone else wants to do 20knts all day, more power to them. I grew up with other power boats an jetskis and friends jet boats, so we have had some experience with all of them.

To each their own.

[Boatsb]

You have naturals. No turbos to worry about and higher compression therefore I believe less issues with wet stacking. The boat will do well at 7 or 8 kts with both running and no downside. It was designed to run that way. A spinning g prop is more drag than a locked one and as much as you want to improve on it your results will not be worth it. Start listening to people who have been through things like this before as their experience is valuable.

[sailorryan]

You have naturals. No turbos to worry about and higher compression therefore I believe less issues with wet stacking. The boat will do well at 7 or 8 kts with both running and no downside. It was designed to run that way. A spinning g prop is more drag than a locked one and as much as you want to improve on it your results will not be worth it. Start listening to people who have been through things like this before as their experience is valuable.

Lol I am listening to others. The conversations I had were outside this forum post and covered literally 20 things we could do. They also suggested I ask if there were additional options beyond what was discussed. The purpose was to find out whether there were 21+ options to do, thats why I excluded some of those things when I posted. This was a think outside the box exercise and I got what I needed, more info.

Fixed vs spinning as with everything "depends." For example, here is an article in yachting monthly from a year ago that computed the drag/math of it all and came to the conclusion that this particular fixed 3 blade created 3x as much drag if you locked it vs letting it spin. Is it the bible? No. Should it be taken with a grain of salt? Of course. Just yet another opinion to take into account. While I have never built a diesel motor from the ground up, my bg is in physics/engineering/mathematics and I have stayed at holiday inn before. I am certainly not the smartest guy by any stretch, but I am smart enough to know to get a wide range of opinions and optimize based on what my priorities are and thats why I talked to others and posted here.

Here is the article for others if they are interested.

http://www.yachtingmonthly.com/gear/lock-prop-let-spin-29526

I am not trying to convince you to change things, as they are right for your setup, etc. I am trying to figure out what my options are for my setup/preferences. Some are obviously better than others, but I will judge that after I have all the info.

[sailorryan]

It really seems that you need to lock the shaft rather than figure out how to lubricate and heat or cool the non-running transmission.

They do make locks for shafts, more often used on sail boats, but I've seen them on big twin engine boats as well.

http://www.shaftlok.com/

http://www.shaftlok.com/

Good info/link to look into. Ironically, if you read the guy who sells the shaft locking device - he says to let motorboats free spin under the following...

"...Because it may help sailors understand the forces and the conditions, let's take a look at twin screw motor cruisers. Consider the case of a faiths twin screw motorboat. Suppose she is running at 12 knots on one engine. (her top speed on two engines may be 20 knots or so.) Her powerful engines will require a large blade area within the confines of the propeller diameter in order to absorb the power without cavitating. The blades will be wide. The pitch will be about as large as the diameter coarse pitched. The speed of flow into the propeller will be around 10 knots. The drag of such a propeller is shown in Figure 3 (15 x 15 propeller). Note that the actual drag involved in this case are hundreds of pounds. Also, a shaft friction of 1 pound - foot only slows the shaft minutely, so that in this case it is clearly better to allow the idle shaft to revolve...."

Here is link btw: http://www.shaftlok.com/FreewheelStoryShaftLok.htm

Elsewhere he shows motorboats that have them and contradicts himself... huh? lol Maybe they have a specific equipment setup/need.

Long story short, it depends on your prop size, pitch, blades etc as to whether you should lock or spin.

[krush]

So the autopilot means ya'll can work and cook while george drives the boat?

[rwappleton]

I have a headache from reading this. It's your dam boat do what the hell you want. What I see going on here is you are trying to convince the center of experience located on this forum that yours is a good idea. Well I'm with the crowd it isn't. Have fun, enjoy your boat and somehow I think we will be reading about you sometime in the future.

[Freeebird]

I'm just glad I had to run on one engine vs wanting to. It sure made the Q&A thing easier.

Question... Is it dumb to think I can run this thing from Palmetto, FL to Chattanooga, TN on one engine by myself?

Answer... Yes