1989 Mercury Classic Fifty 45hp Timing Screws Identification

[Mattwill00]

Hello everyone

My buddy and I finally made a boat purchase and are having some issues with it. We took it out the first day and it was bogging and had an issue with a rotten fuel line in the tank. Fixed that, rebuilt the carbs & fuel pump, verified spark on each plug. Figured that would do the trick. Took it out again to tune the idle air screw, and the boat still ran like garbage. After looking around at the throttle arm, the locknuts on the screws were halfway up the shaft and the screws were moving freely. So we went ahead and purchased a timing light, but we want to identify the screws before we really start messing around with them. This will be my first go at timing an outboard and we found a write-up regarding how to approach it, but some screw identification would go a long ways. Thanks everyone! We also plan on checking the exhaust and the reeds before we head back out on the water.

Here’s a picture of the throttle arm. Screws number 1,2,3 would be great to identify.

 

[Mattwill00]

My current guess is 1. Max advance, 2. Full throttle, 3. Idle stop? Any insight would be greatly appreciated! Thanks

 

[Faztbullet]

Ding...ding...ding..Folks we have a winner!!!

 

[Mattwill00]

My next question is how to time this thing….

Set TDC on the indicator pointer

Set the primary pickup to fire at 7-9 deg BTDC by adjusting the max advance screw (cranking motor + timing light)

Set WOT to fire at 32 deg BTDC using full throttle screw (cranking motor + timing light)

Forgive the ignorance this is my first real go at timing anything. First real go at an outboard in general…

 

[jimmbo]

Have you got a Good(Factory) Service Manual?

 

[Mattwill00]

Unfortunately no. The only one I’ve found has the worst pictures I’ve ever seen and very little identification diagrams. I’m really basing this stuff off of what I found in that manual plus what I’ve found here. That’s it really in a nutshell. I guess I’m just confused as to what the “pickup” screws refer to.

 

[jimmbo]

On these engines, there is NO Idle Timing Spec, as the Timing is retarded to what ever it needs to be to get the correct Idle Speed. The Carbs are fully closed at Idle, and in most cases barley open until all the WOT Timing has happened. Pickup Timing refers to where the Timing has to be when the Throttle Shaft on the Carb(s), is at the point of moving off of Fully Closed ever so very slightly. Some engines have more than 1 Pickup Spec, a Primary and a Secondary. Specs can be different between Models, and even Years, and Throttle Linkages can change. so it is important to have the correct info.

 

[jimmbo]

Oops duplicated post deleted

 

[Mattwill00]

 

[Mattwill00]

This is what I’m working with this far. I did find the specs for primary and WOT (7-9 deg, 32 deg BTDC) at the back of the manual, I guess I’m just confused on the wording of the manual. Thanks for
being so helpful too, I know this stuff might seem pretty elementary to some folks here. Im really just hung up on what screws to adjust when.

 

[Mattwill00]

So for the primary pickup timing, set it at the correct timing spec when the carb is just barely opening? And use the full throttle stop screw? Then use the WOT Screw and set to 32 degrees? I think I’ve got it… some confirmation would be awesome though! Thanks for the help