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

[don thompson]

We are currently compiling a briefing list for a design that will ideally incorporate a twin engine design into an aluminium hull with moderate v (deadrise) aft.
This will be a follow on from the current 7.6 mtr, single engine, hamilton jet powered fishing boat, designed by Gavin Mair of Global Marine Design in West Australia and which has been an excellent vessel.
can anyone comment on the issues regarding the canting of engines and any inherent problems such as design/installation problems and wear of engine/pistons due to gravity effects.

[Ad Hoc]

Your SOR is nothing new, it is not reinventing the wheel so to speak. There are plenty of twin engine installations out there, ie, it isnt a problem. You need to separate what you mean though....between twin engine and canting, the two are different!

However, if you're enamoured with the G.Mair design, why not ask his opinion?

[don thompson]

Thanks, sure there are plenty of examples but just to clarify that I see two aspects to the issue.
One being the initial layout/design and how to go about the set-up, associated problems and particularly any solutions.
The other is mechanical and primarily an issue of laying engines over on their side to match the dead-rise. Perhaps there is some useful experience out there re; reliability problems.

[CDK]

Make sure the suction pipe of the oil pump stays submerged when the oil level is low, like during turns and acceleration.

[gonzo]

Detroit Diesel modified some engines to be installed on their sides. You could check their specifications to see how they solved the problem.

[don thompson]

yes thanks Detroits,(rare on this side of the Atlantic) and location of the oil pump are the sort of pointers I was after.Other question marks over the fact that the pistons will potentially always wear heavier on one side of the bore.
Our family business has built owned and run a number of vessels over the previous 3 decades but totally new to the concept of twin engine jet set-ups, hence the search for possible solutions and examples ie can the engines sit upright despite the dead-rise angle

[CDK]

Except for the oil level restrictions, engines can work in any position. Think about boxers and star engines.
If you need a considerable tilt angle, also make sure the oil level has enough clearance from the pistons in bdc.

[gonzo]

Some engines have squirt holes to lubricate cylinder walls or other parts. That would be, IMO, the most critical part to modify. The oil spray should be able to lubricate the part adequately.

[Mr Efficiency]

http://autospeed.com.au/cms/title_Th...4/article.html
Seems that canting was no problem for that one.

[speedboats]

Why cant the motor? Just simply mount the motor level. The drive couple doesn't care that the base plate of the jet pump and the motor block are rotated around the drive line.

[whitepointer23]

totally agree with speedboats, why the hell would you cant engines in a jet installation. the hamilton jet would have to be easiest inboard setup you could do, there is no need to complicate things when you are running a driveshaft.

[don thompson]

It depends what you consider as complicating things! The most straight forward option to my mind, is to have jet, g,box and engine all in the same plane. There is a second consideration more applicable to fishing and work boats in that mounting engines level will result in a decrease to deck space (higher engine box) and a reduction in stability figures.

[whitepointer23]

your boat mate, you know what you want. i just don't think canting engines is as straight forward as you think .

[CDK]

Originally Posted by don thompson

The most straight forward option to my mind, is to have jet, g,box and engine all in the same plane.

Yes, that's the way to do it to get long life and little maintenance of the universal joints.

[anthony goodson]

I have always set universal joints at least 4 degrees out of line ,and do you really need the gearbox?