twin in aluminium moderate v - canting of engines and any inherent problems?

Yes, it is a good idea and your engine manufacturer will have specs for how far their product can lean. Stock, probably not enough to match the deadrise but you can simply ask the manufacturer what the issues are and the right person there will work with you. They want to sell you engines... You may need to set up maintenance from the outboard sides.

 

Each engine is different and may or may not give you a problem leaned on it's side. As mentioned oil pick up is the #1 concern, trapped air in the oiling and cooling system can also be a problem that may not show untill you've been running for a while. Best bet check with Manu or set it up to opperate in it's "design" position. A better option to get the motor as low in the hull as possable might be to fab an oil pan and pick-up to match your deadrise, keeping the motor in the up right design position.

 

how do you think uni joints will have less maintenance if there is no angle, they need some offset or they wear out quicker.

 

Perhaps sarcasm?

Here's a pic I've posted before showing the mounting of twim jets, I don't however have one with the engines installed (level) You can see in the pic that the pumps are installed quite close together which means that the engines are real close (I could slide my hand between the exhaust manifolds of the V8's. Most engines are quite square on top, so I am wondering how much height (if any) you would save by canting?
You can also see the spline of the mainshaft and how easy it is to rotate the engines around the mainshaft without any detrimental outcome (This boat is comercially run in Zambia without alignment based issues)

 

In mechanical engineering there two opinions (read religions).

1. A small angle will keep the bearing grease in motion, ensuring lubrication.

2. An angle causes irregular angular speed, increasing vibration and load on splines and gears.

With flexible mounted IC engines in a hull there will always be radial movement and misalignement, no need to purposefully add an error.

 

I hesitate to take issue with you CDK your knowledge in most areas is far superior to mine ,however I understood from an early age that a universal joint needs an offset,without it the needle rollers in the yokes don't "work" and as a consequence they seize up. 4 degrees was suggested as optimum .Is this incorrect?

 

No Anthony, the 4 degrees is a viable theory.
If perfectly aligned, the bearing rollers are poorly lubricated. But in that situation you probably don't need uni joints at all or choose sleeve bearings.

 

Good Morning ,CDK thanks for clearing that up, Tony

 

Keeping the mainshaft and crankshaft on the same angle (perfectly aligned) but shifting them to different planes (offset planes) puts corresponding angles at both sets of crosses, therefore does not the angular velocity at one end cancel out the other end (inverse wave form)?

 

In theory that's also true if you can ignore the mass between the crosses (CV joints). A drive shaft with crosses at both ends is always kept as light as possible because the mass causes vibration.

But it is all theory. In a vehicle, especially a grp hull, I would try to line up the parts as good as possible, knowing that it will never be perfect.

 

The best way to run twins in a jet boat is to stagger the engines so you can put the intakes down low close together.

There is an excellent article on this in POWERBOAT July 1972 by Dick Debartolo;Ralph Rhoda(one of the original jet drive engineers)was the consultant.

We built several hi performance twin jets with staggered engines and they performed well;no cavitation,pump unloading and excellent weight and balance.
We always kept the engines level.

 

Has anyone ever tried a hydraulic transmission? I ask because if I can give benefits in a project of Amphibian ..