Shaft Rotation Question

[By Invitation]

I have a Perkins 4-108 which when looking at the boat standing at the stern and looking towards the bow, the engine rotates "counter clockwise". My Output shaft on my transmission also rotates "counter clockwise" when in Forward. My prop rotates "counter clockwise" when going forward - so far so good. I am installing a new transmission with a gear reduction and I have been told by the company who reuilt it, that it is a "left hand rotation".

My question is - Does this mean that my prop rotation when going forward is the same as my original configuration? "counter clockwise" - I hope so and am just asking anyone to confirm this because I am ordering a new feathering prop for this and it ain't cheap.

Thanks

Scott

[Alan Wheeler]

Yes.
But I would pose all those questions to the Prop supplier to be doubly sure and ask them if you can have a free return and swap, should you all have made a mistake.

[BC Mike]

The rotation of the engine is usually determined by looking at it from the front and they usually go clockwise. The prop is usually referred to as a left hand or right hand and is usually right hand or clockwise when viewed from the stern.
Michael

[GordMay]

Prop Rotation in Forward Gear, viewed from Astern (as viewed from behind boat looking forward):
Clockwise rotation is Right Hand
Counter-clockwise rotation is Left Hand

Cannot see the rotation? Put the shifter in reverse. If in reverse the stern kicks to starboard then you have a left-handed prop; if to port it is right-handed. Because of the “handedness” of the propeller the boat will always kick the stern to either port or starboard.

The prop' should be stamped with the pitch & rotation.

[Steve Kidson]

Scott,

Cannot help with any additional input re your rotation issue, but I would be interested in any info or your experience/impressions/performance of your engine; I have just purchased same engine second hand to power my yacht.

Thanks in advance

Steve

[CSY Man]

in any info or your experience/impressions/performance of your engine; I have just purchased same engine second hand to power my yacht.

What would you like to know?
I have lived with a Perkins 4-108 for 6.5 years and have become quite intimate with the beast.

[Maddog]

I have a 4-107 as is virtually the same as the 4-108. Before you install it, replace the oil pan gasket. The gasket for the engines include little cork tabs at the front and rear, These are the first to fail causeing your soon to be, future oil leaks. I am told there is not a better replacment gasket to solve this.

I would also install a permanent tube and pump from the oil pan to faciltate oil changes. Sucking it through the dip stick dosen't always work well.

If possilbe, place a small sump under the pan to catch any leaking oil and keep it out of the bildge.

I wish I had all these things.

This engine is a workhorse and just might outlast the boat. Mine is the original from 1970. I knew the original owner. To the best of my knolwedge. It has only been rebuilt twice in that time. Still starts and runs great.

The info on the gasket came from my mechanic when I inquired about an engine rebuild.

[Steve Kidson]

Thanks guys for the input so far.

Motor has not long been installed, and had new gaskets just prior to my purchase, but a drip tray is a good idea, and I certainly have the room. New polymer mounts were used in installation, with the added advantage that these mounts electrically isolate engine from hull. Polymer shaft coupling completes the isolation circuit.

Mine has an oil change pump fitted to the starboard side of the block, makes the task quite easy.

Further info that would be useful includes optimum engine speed, operating temperatures, estimate fuel consumptions. I understand that these Perkins are almost bulletproof, but any areas to be aware of that might be vulnerable.

The installation is for FWC with a heating loop to heat a hot water tank. Engine drives through a Hurth transmission with 3.2, (I think) reduction, 1" stainless steel shaft, - I have yet to settle on a prop. Boat is 32' long, ferro construction and according to designers specs, will displace approx 7 tons.

Fuel is fed from 2 separate tanks, and each has its own CAV filter. Fuel returns to same tank drawn from. Tanks will be used independantly of each other, and fuel returns to same tank drawn from.

Any insights that relate to any of the above will be gratefully received.

Cheers

[Alan Wheeler]

Sounds like you have it all sorted. Yep Perkins are a good reliable work horse and Parts are cheap. Ensure you run a corrosion inhibitor and it should be sweet. If you have a transmission cooler, ensure you check the trany oil for water contamination as part of your maintanance schedule.

[CSY Man]

My 4-108 has a max RPM of 4000, with max contiuous 3000.

Most efficient is 70% of max c., =2100.

I run a 16X10.5 prop on a 33 foot sailboat, displaces about 12 tons loaded.
Figure about .5 US gallon per hour @ 2100 for 5.3 knots

Injectors should be cleaned every 400 hours or so and valves adjusted every 1000 hours.

[Alan Wheeler]

You maybe a little over zealouse with the hrs to maintanance schedule. I would happily double those hrs. To put it in perspective of a vehicle, you usually look at injector work at about 80,000Kms(50,000miles). I work on the rule of thumb of 1hr=100Kms/60miles.
Using a good injector cleaner/lubricant can add years of life to the fuel system. I mean a good sysnthetic. Some are just copeouse quantities of Kero. Amsoil & Wynns are two I recommend.
Be vary wary of anything containing Teflon.

[Steve Kidson]

Thanks guys, I'll add all the info to the data bank. I'm confident we should be mostly trouble free.

Cheers

Steve

[Maddog]

There's some nof I didn't know. These are all good replys.

I'm curious about the rpm's. I get to hull speed at 1700. Do you really run it at 2100? What kind of prop do you have? 2blade 3 blade? My boat is close to the same size but not as heavy.

[CSY Man]

You maybe a little over zealouse with the hrs to maintanance schedule.

Huh me?

the above numbers are as per Perkins..400 hrs for injectros and 1000 for valve adjustments,
Granted, the book was written 26 years ago and now we have better fuel, filters and lubes...And even more lazy operators.

I'm curious about the rpm's. I get to hull speed at 1700. Do you really run it at 2100? What kind of prop do you have? 2blade 3 blade? My boat is close to the same size but not as heavy.

Ya get hull speed at 1700 RPM...?

Seriously over-propped maybe?

I get the 6.5 (sail) hull speed @ 3000 or so.

There is however 2 kinds of hull speeds: One under sail and one under power.

On my boat the sail speed is around 6.5, and power 7.3.

To get the "power" hull-speed however I have to run close to 4000 RPM and that is just not happeing on my old boat..Can't afford to rebuild the engine and tranny every 6 months or so.

Ya should get 90% of max RPM under power with the right size prop.

I got a 16 X 10.5 wide 3 blade prop...Think tug-boat prop.

Plenty of drag under sail..But aye so good under power.

[Maddog]

Interesting. I belive my hull speed to be 6.5 Which I hit at 1700-1800. I have to admit I don't know the size or pitch of my prop.

Is there an internet source I can go to to find out. I plan on reproping with the kiwi prop next summer. It would be good to have some info before I made that purchase.