Honda 135 navy usage question. Help!

[NavENG]

1)I work for NSA GAETA IT, we are using honda 135 and 150. The navy is cutting down on cost for our HSB RHIB's 8meter usage. So our superiors want to know if what will happen if we only use one single 135 engine instead of two on our HSB for 1 week evolution. Would one engine be to much of a load to handle for our HSB? We currently have two 135 motors mounted on it and i'm pretty sure navy put two 135's for a reason?

2) what damage can leed to continously start and stopping the motors in a short period of time?

3) what would happen if we idle both engines for a 8 hour or more evolution?

thank you for the feedback.

 

[KCJ]

1) The main reason for twin engines if reliability. One engine may fail, but seldom both. Yes, more power can be had, but even a towboat isn't towing all the time. Cruising at 40*>60* % throttle on 1 engine and rotating engine useage ever 4 hours shouldn't cause a problem. If you need WOT fire up the second engine.

2) Starting an engine is hard on it. It puts extra ware on cylinders, starting systems and the batteries might not have enough run time to fully recharge.

3) Extended periods of idling can lead to cooling problems and carbon build up.

Just my 2 cent worth, hope it helps.

 

[chawk_man]

This is the first time I’ve ever seen a government agencyask for advice on a public consumer forum like this one, so I am skeptical. ButI’ll bite.

First, let me clear up what you are asking. From your message, I’m assuming you are not intending on dismounting one of the engines, but just operating on one engine at a time. Is that correct? And the second engine would always be available if needed, is that correct? So, the inquiry from the brass really has to do with savings in fuel, maintenance, and extending the longevity of the engines. Is that correct?

The answer to your questions then depends on your operating environment. If your 8 meter RHIB is rigged like a typical CG rig, then a single 135 is too little power, unless you are just tooling around in small lakes, rivers, and ports in calm seas. With only one engine, and a typical setup, the weight will make it difficult to get up on plane, and when you do, it will not be stable. Besides that, all your potential savings would disappear because you’ll need higher RPM’s to maintain the plane, and the engine will be wearing faster. If you map the efficiency curve – RPM vs. MPH/KPH vs. GPH – for your particular crafts, in both duel engine and single engine configurations over a range of operating situations, you will likely see that the fuel savings would be minimal if you need any significant speed.

Also, I’m not an experienced RHIB boater, but it seems that the bigger ones almost demand a duel engine set-up for stability and maneuverability. With that shallow hull and typical weight, you’ll need both engines for maneuver, especially in high crosswinds and heavy currents. Also, if the operators are not highly experienced boaters, docking a single engine boat in tight quarters with a high crosswind can be a real challenge.

 

[NavENG]

Thank you for all your inputs. Answer some question about why going to forums working for the DOD. You figure i work have all the answers right? Pretty much I'm working outside my field on these boats, my past experienced using forums never disappoint me plus going to the marine engines field is pretty different from land base engines. but enjoying it very much.

 

[hondadude]

I agree with Chawk....

If you run on just one engine, that engine will not be propped correctly for single engine operation with that boat and the engine will overwork itself. It will be like trying to drive up hill from a stand still in high gear in your car.

It will definitely be unstable with one engine at high speed. Actually...unsafe.

The starting and stopping question depends, as he said on how long between starts. We service a boat that sample water in the Ohio river with twin 150's (same basic engine as the 135). They have to start and run hard a short distance.....stop....take a sample and then another short run to another sampling location...etc, etc, etc. Constant starting and stopping and there seems to be evidence of harm to the engines. They have a couple thousand hours on them.

Bottom line...you may use a little more fuel running the two engines, but the engines will last longer and the boat will run safer.

Mike