engine rotation on twin Inboards

speakrdude

Well-Known Member
Feb 21, 2009
1,214
Northwest Arkansas
Boat Info
2002 Sea Ray 340 DA
Raymarine C80 Tri Data
Engines
twin 6.2 MX MPI
On my 88 model 300 Weekender with twin 350/straight inboards, I believe the port engine to be standard rotation and the starboard to be LH. Does that sound right?
 
On my 88 model 300 Weekender with twin 350/straight inboards, I believe the port engine to be standard rotation and the starboard to be LH. Does that sound right?

The way I understand it...looking from the flywheel end, LH or counter clockwise is "standard". That's the starboard side. Reverse rotation is clckwise from the flywheel, that's the port side.
 
YES That is correct kind of.... the engine s might be the same rotation, but the props may be counter rotation....

This answer is only "kind of" correct... Props only turn the direction that the shaft there attached to turn. Counter rotation is accomplished by one of 2 ways, either the engine is counter rotation or the transmition is counter rotation. On older model inboards (early 90's) the engines were counter rotating and on the newer models it is done through the transmition.
 
I looked at my props this morning, and while I don't know if this is factory, but the port side has a left-hand prop and the Starboard has a RH prop. So does this mean they are both "more-than-likely" std rotation?

Port Side

2146307240053136314S425x425Q85.jpg


STB side prop

2771930680053136314S425x425Q85.jpg
 
Your starboard prop will turn clockwise and your port will turn counter clockwise.
 
Your starboard prop will turn clockwise and your port will turn counter clockwise.

OK...now I'm confused. If the starboard engine is LH, counter clockwise, as viewed from the flywheel, why would the starboard prop turn clockwise?:huh: Unless...prop rotation is reversed in the transmission?

Not long ago, I called my engine Mfg, gave them ser. No.s of port & starboard engines. They confirmed that my starboard engine is standard or LH viewed from the rear and my port engine is reverse rotation or RH.

Another CSR member just replaced his original port reverse rotation engine with a new reverse rotation engine. http://clubsearay.com/forum/showthread.php?t=15829

To add more confusion...I just spoke to a MM mechanic and was told that the starboard is clockwise or RH (which is standard) and port is reverse or LH counter clockwise on the older boats. His rule of thumb...rotation is top of flywheel or prop towards the outside of the boat when viewed from the rear. So I had , in my mind, the rotation for standard backwards. Standard is clockwise from the rear and is the starboard side.
 
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I confirmed that the old starter from the Port engine last night, that the flywheel of the port engine turns counter-clockwise as viewed from the rear. I have yet to turn over the Stb engine that is IN the boat. Who knows, maybe the stb is ccw and the port is cw. Or maybe the PO installed the wrong engine and then blew her up. I did discover the distributor, which was laying the bilge from the port engine, was missing the roll pin that holds the gear in place to the dizzy and the oil pump. That'll sure do it. Had that happen once before with a 3.0lx. Engine and dizzy kept turning, however the oil pump was not.
 
Port side is counter rotating, starboard is (standard) clockwise. Just remember though I think all boats from the 80's are going to have counter rotating engines on the port side. Inboards (gas) from the mid 90's on up will have 2 Clockwise rotation engines with the port transmision being counter rotating on the final drive side. You can usually hear a counter rotating trany, they have a little different whine to them.
 
Quote:

To sum it up: Whether CCW (standard) or CW (opposite) rotation, it is always defined as the direction of rotation when looking at the flywheel or output end of the engine...

End Quote

the definitive reference for this question :
http://boatdiesel.com/Articles/Articles.cfm?P=20090101_Introduction.cfm

Again, as others have stated, engine rotation is one thing; how the prop rotates depends on whether you have a reversal or not occurring within the transmission.

Many straight inboard older boats (like mine) have velvet drive transmissions where the transmission rotation is the same as the engine's rotation. Since the prop rotation needs to be different for port and starboard, this is accomplished by using a counter-rotating engine on the starboard side, also known as a RH = opposite = clockwise = non-standard engine. Again, it is defined by looking at the flywheel.

V-drives may result in your port engine being a counter rotator, or not, depending on whether the transmission changes the input rotation. Clear as river mud, huh ?

Anyway read the article - it expains it way better than I can.
 
I went to the rebuilder to look for clues as to which engine this may be. It appears to be std. rotation. I found a Mercruiser Option Code tag that looks like it came from the valve cover. The code is 111511204S260. I dont have the decoder here in front of my but if I remember correctly, that indicates Std rotation 260 HP.
I am really starting to think the PO put the wrong engine in the wrong place. The other engine is Chevy Orange. I will investiagt further.

More to come.
 
I went to the rebuilder to look for clues as to which engine this may be. It appears to be std. rotation. I found a Mercruiser Option Code tag that looks like it came from the valve cover. The code is 111511204S260. I dont have the decoder here in front of my but if I remember correctly, that indicates Std rotation 260 HP.
I am really starting to think the PO put the wrong engine in the wrong place. The other engine is Chevy Orange. I will investiagt further.

More to come.

I don't like that Chevy Orange in a boat...might be a car engine...not good. I think the reverse rotation motors have a conspicuous "R" somewhere in the serial number. Also I think you said the port engine's starter looked to be turning in the correct direction. In any case you have some detective work to do to see if you have a clockwise standard for starboard and a counterclockwise for port.

You mentioned before about the dizzy and pin being sheared on the distributor shaft for the port engine.(?)
This is a long shot but I wonder if the PO tried to convert a standard engine to reverse by swaping to a reverse distributor?...or put a reverse cam in the standard engine and tried to use a standard rotation distributor?

I have done a bunch of small block Chevy's but never a reverse. I think what gets them reversed is 1. a reverse cam. 2. a reverse distributor and 3. oil pump has to work in reverse rotation. Is this right?
 
Well, I confirmed it. Either the PO has the wrong engine in the wrong spot or the wrong starter. Or maybe a little of both! Maybe thats why he gave up.

The Stbd (orange) engine spins, from the rear of the engine, viewing the flywheel, Clockwise! Thats reverse, right? So now, I have even more investigating. I bet they didn't get it started. No wonder why the throttle cable, prop shaft, misc. stuff wasn't connected. :smt021

I still think she a diamond in the rough!!
 
Well, I confirmed it. Either the PO has the wrong engine in the wrong spot or the wrong starter. Or maybe a little of both! Maybe thats why he gave up.

The Stbd (orange) engine spins, from the rear of the engine, viewing the flywheel, Clockwise! Thats reverse, right? So now, I have even more investigating. I bet they didn't get it started. No wonder why the throttle cable, prop shaft, misc. stuff wasn't connected. :smt021

I still think she a diamond in the rough!!

Clockwise from the rear for starboard is good. Does the port engine look original? It should be the reverse engine. Get the S/N for it, contact Merc or Crusader or MPI or whoever's motor it is and confirm.

Now I'm thinking the orange motor is a replacement for a f**d up motor that the PO took out. Check to see if it has brass freeze plugs...if not, start looking for a boat motor. If it does, get it's S/N and find out what it is. I don't think Chevy painted engines orange after about '73~'74...God only knows what it is.

Is this boat set up like and Express Cruiser with straight drives or is it like a DA with the motors in the rear with V-Drives?

You'll sort it out eventually.
 
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