bertram31.com

I have a 28 bert FBC took out starb engine in fall had a slight knock to it. Tore down engine and to my surprise had timing gears not a timing chain I thought port engine was counter rotating engine, but know i will need to check rotation on that engine. I have heard that some boat manufactures put them on any side and just change trans direction,my question is what side did Bertram usually put these on. Thanks mike

If I remember right, looking towards the bow, the one on the starboard side turned Clockwise and the port counter clock wise. The props always turn outboard.

Port on mine.

Just removed my starboard engine , It's reverse rotation.

Starboard engine and the the prop turns counter clockwise?

Huh!

ok so the real answer is????

Now to totally confuse us:


Which Way is Which? Marine Engine Rotation Explained



People are often perplexed when trying to replace their starter, distributor, camshaft and or engine oil seals and the parts are specified by engine rotation.


Engine Rotation

Rotation is always determined by looking at the flywheel end of an inboard engine. The flywheel of a standard rotation engine turns left, or counter-clockwise, when viewed from the flywheel. The flywheel of a reverse rotation engine turns right, or clockwise, when viewed from the flywheel. Most single engine inboard and I/O boats use a standard rotation (L.H.) counter-clockwise engine. Use the illustration to the right, courtesy of API MARINE, to help understand engine rotation.

If your boat has twin engines, counter rotating engines have long been used to neutralize propeller torque which improves vessel handling and performance. The port, left side engine, is the standard rotation engine. The starboard, right side engine, is a reverse or counter rotation engine. Sometimes it is not possible to view the flywheel so engine rotation will have to be viewed from the front of the engine. Just remember to reverse what you see at the front of the engine so it agrees with flywheel rotation. These are the guidelines for engines mounted in the normal fore and aft position with the flywheel closer to the stern of the boat. Some older boats used a flywheel forward configuration that can change the rules. Also, some ski boats with single engines, mostly Ford 302/351 power plants, used reverse rotation engines so it is a good idea to determine your engine’s rotation before visiting the parts department to avoid error.

Due to the higher production costs and the advent of fuel injected gasoline engines bristling with computer modules and sensors, engine manufacturers discontinued reverse rotation engines in most cases. Since then, engine outputs have been handled by reduction gears capable of reversing engine output rotation. Both engines are standard left hand rotation but the reverse reduction gear changes the starboard engine output to right hand rotation. This is a much simpler, less expensive way to handle the need for opposite rotating engines.

Starter motors, when mounted forward of the flywheel, will turn clockwise (R.H.) to start a standard rotation (L.H.) counter-clockwise motor. Starters mounted aft of the flywheel will turn counter-clockwise (L.H.) to start the same engine. Everything is just the opposite when speaking of a reverse rotation (R.H.) clockwise engine.

Article by: Michael Weller

Or use ZF gears and forget rotation! Ok tony now that you are all twisted ; which side do you put the stronger engine when they come off Dyno with 3 or 4 hp difference.i doubt you can google that one.sleep on it .you have the most important factor correct "both props must turn to the outside "

After reading this and thinking about, I was probably wrong. Sorry for the bum steer.

To Answer Bobs question, assuming he is referring to two standard rotation motors going through ZF transmissions. Put the strong motor on the port side. To get outward turning prop on port side requires three gears (two direction changes) and getting outward turning prop on the port side requires two gears (one direction change). So a slightly larger loss on the port side.

Bertram 20, The motor with timing gears rather than a timing chain is the counter rotating motor. This allows the crank shaft to turn in the opposite direction from the cam shaft (with chain they both turn the same). This arrangement means that on the counter rotating motor the cam turns standard, as well as the oil pump (both motors use the same pump), and distributer. On most older marine distributer caps you will see to sets of firing orders. The larger writing is standard and the smaller writing is counter. Since you have the motor at least partially apart, try hard to keep the timing chain (gear) cover in good shape. The timing pointer is on the opposite side and the reverse covers can be difficult to find. Also, be aware that the water pump (fresh water) may be unidirectional. I have seen right hand turning, left turning turning and ones that work both ways. another very important item, if you are replacing the pistons (or re-installing) they have to go in backwards (the notch pointing to the flywheel and not forward). This is due to piston pin offset.

Have fun!

Bill

Bill you mention the pistons orientation -------- ok you paid your dues your another great asset on this board .

awesome thanks for all the info

Bob

I don't think the slight difference in HP will even be noticed once installed. Too many factors at play to make that much of a difference, plus I am not racing her.

Is still stand by the starboard side turns clock wise. Your HUh and Raleigh threw me for minute hence the search.

I guess I needed to fact check Rawleigh. God I miss Mitt Romney.

Tony Meola wrote:Bob

I don't think the slight difference in HP will even be noticed once installed. Too many factors at play to make that much of a difference, plus I am not racing her.

Tony,
I'll stick by Bob on this one. While one individual factor may seem meaningless in the scheme of things...it's when you start doing several seemingly meaningless projects that things start to come together and add up. It could be more speed, savings, performance or range. Will you get a payback on the investment....maybe, maybe not...but if it a free 1/10 of a gallon of fuel saved every trip for mounting a motor on one side vs the other...I'll take the free gallon on the 10th trip.

Tony mounting on the correct side will play a role down the road.you would like both engines to respond dead nuts equal as you put one hand on throttles and look in front of boat as you " put her into the wind" . My starboard engine puts out 314hp and port produces 310 . The " sticks" are dead even all the way to 2950 cummins 315 hp. They top out at wot. Exactly the same rpm on tach. Rule number one always put the stronger engine on starboard! I do this all the time even with gas engines.every "trick" counts" for fuel economy especially now with a country who has a leader determine to destroy small business by way of payroll taxes

Just went through this issue and it was the port side counter rotation.

Bob and Carl

How many new boats come out without the manufacture putting those engines on a Dyno. Also, how many repowers is it even thought about.

Since I never raced, this never really came up. But for hose that are really into making sure you have every last bit of power coming into play, I have question. Bob or Carl, after lets say 300 hours on the engines, if you pulled them and put them back on the Dyno, would the HP difference still be the same? I figure wear and tear have to have some impact on the engines performance.

The answer is yes quite evenly providing the parameters were kept the same like maintenance .quite annoying piloting a boat with boat throttle out of whack to keep rpm even. One engine dragging is usually evident under servere load like getting on plane . Hope this is helpful

Bob

Interesting. I would have thought after a point the difference in HP would change due to the difference in wear on each engine.

I have a 1972 Bertram 31 and I'm looking for a port engine counterclockwise rotation MERCRUISER 7.4 FRESH WATER COOLED INBOARD ENGINE 340 HORSE POWER.
Does anyone have any suggestions on where I can go to find one please. 978-895-7449
Thank you.
Jamie jones

The forum "The Hull Truth" has a big swap and sell topic and has many members all across the nation. I would go there first

Jamie

I know nothing about this dealership, but they have a counter rotating engine.


https://www.atlanticmarinestore.com/7-4-454-engines/

https://www.michiganmotorz.com/7-4l-454 ... plications

By the way, the Starboard side get the counter rotating engine.

If you cannot find one, you will need to replace the transmission and let the transmission reverse the rotation for you.

He is indicating counter clockwise rotation, not counter rotation.
That would be Port.
Looking from the rear engine and prop turn left hand.

Doesn't say new or used or rebuilt which would be helpful on directing him to the correct place.

Bruce

Nice I missed that.