Engine Pulls to the Right

[Olde Merc]

I have a 1978 Merc 200 20hp with a till handle. It is mounted on a early 1990's Legend 14ft deep and wide 14' aluminium boat. <br /><br />When I run the boat at high speeds, the engine pulls hard to the right. If I took my hand of the till handle, it would pull to the right VERY fast. I had the motor bolted to the boat and it is perfectly centered. What could be the problem? It seems unsafe that it pulls so hard. Does anyone have any ideas?

 

[ivar]

Re: Engine Pulls to the Right

You have to adjust your trim tab a little to the right.

 

[Olde Merc]

Re: Engine Pulls to the Right

I haven't worked with boat engines much before, but I am pretty handy with engines. So, what is the trim tab exactly? Is that the fin under the prop that needs to be adjusted? Just bending it will adjust it?

 

[BKool68]

Re: Engine Pulls to the Right

It is the tab on top of the prop. There is a bolt thru it that will loosen and alow it to turn.

 

[Olde Merc]

Re: Engine Pulls to the Right

My engine doesn't have a trim tab above the prop. It looks to have a flat metal plate where the tab should be located. I am not sure if there would be room to add a tab though, as it looks like the prop would hit the tab.<br /><br />I have a picture of an older Merc that has a bottom end similar to mine. Is there anything I can do?<br /><br />

 

[ivar]

Re: Engine Pulls to the Right

Not sure on your Merc. , but usually the tab also serves as a sacrifical anode to prevent corrosion. Does it look like the plate is corroded in any way , and the tab could be missing?

 

[Olde Merc]

Re: Engine Pulls to the Right

I just went out to the boat and checked the flat plate. It looks to have not ever had a fin on it, and it has no signs or corrosion. But I don't think that there would be room to add the tab anyway. There is probably only half an inch clearance above the prop. Look at that photo of the Merc I posted. There is no room for a tab, just like my engine. <br /><br />Is there anything that I can do at all?

 

[KCLOST]

Re: Engine Pulls to the Right

Olde Merc.<br /><br />Here is a link to a message board that is totally dedicated to old Mercury motors... They will probably be able to help you.... One thing I'd like to mention is that there is room for a Trim tab if the tab extended downward behind the prop. It's a possibility that you can get one that will fit that motor....<br /><br /> http://www.pfs-ware.com/kwast/mercboard/index.htm

 

[ivar]

Re: Engine Pulls to the Right

Sorry, didn't see the pic. had turned off pictures in my browser.<br /><br />If there was ever supposed to be a tab there at all , it would be situated behind the prop , not above it.

 

[Eldiablo]

Re: Engine Pulls to the Right

I'm not sure about yours, but a friend has the same exact motor as mine and one day I looked done where his zinc anode trim tab should be (i was just working on mine) and his was perfectly flat, the zinc disc was still there, but the tab had coiroded (?) away. I ask him if this was for racing, and he looked at me and said there was never anything there.<br /><br />my point is that it looked so perfect without the tab. just cause its not there doesn't mean it wasn't.

 

[Olde Merc]

Re: Engine Pulls to the Right

Okay that would make more sense that the tab would go behind the prop. The plate seems to big enough that it could have a tab behind the prop. It sure looks like there wasn't a tab on the plate before. <br /><br />Now, how does that plate come off? I guess I would have to got to a Merc dealer to get the trim tab?

 

[Eldiablo]

Re: Engine Pulls to the Right

they have pretty much standerdized anodes lately, and you can get them about anywhere, even walmart, but if i were you and had an old merc, I would seek the advise of a dealer first, or at least ask for the parts desk and see if such an animal exist.

 

[KCLOST]

Re: Engine Pulls to the Right

Olde Merc,<br /><br />I am not familiar at all with your motor, but if you look above the trim tab there should be a bolt/screw that holds it in place on the lower unit. If you look at your motor or pic, look above the prop on top of the extended housing above the prop. Right at the very rear (at the top) or very near the rear of that area that extends behind the prop (a branch is touching that area in your picture) there should be a hole or a cap that gives access to a hole, that holds the bolt/screw that secures the trim tab. If there is nothing there it is probably accessed by removing the lower unit... But don't remove it until you get proffesional advice because I'm not sure about that...

 

[Jango]

Re: Engine Pulls to the Right

I have a 75 200 merc (20HP) and there is NO TRIM TAB and never was. The bottom of the lower unit could be bent, but probably the steering is just loose. Try tightening the steering resistance screw. (Large Hex head located on top of the tiller arm, under the power head.)

 

[Olde Merc]

Re: Engine Pulls to the Right

I have noticed that the steering is quite loose. Maybe I will tighten it before I try anything else.

 

[Olde Merc]

Re: Engine Pulls to the Right

I tightened up the steering resistance screw and all is fine. Now I can let go of the till at WOT and it stays nice and straight. Thanks for the tip!