I am in the process of doing a sync and link for the first time on my old 92 Mariner Magnum EFI. I've been told it is the exact same engine as a 175 Mercury Black Max. It runs good on top end, but has some idling issues. I have had it for two and half years and have fought these little nuisance issues since buying it. I am not one to go to the shop though, can't stand the thought of paying almost 100 bucks an hour for labor. Finally got the motivation last night to read up on the process.
One thing I found was pretty startling to me. Going through the process of lining everything up in the throttle linkage, I found the injection pump linkage very odd. When at full throttle, I noticed the linkage was binding severely and rubbing the fuel evaporator canister or fuel bowl and thought to myself, "this can't be right". I checked the alignment marks and there was no way that was right. What I figured out was the linkage had at some point flipped 180 degrees and was now going counterclockwise at full throttle instead of clockwise like it is designed. I corrected it and aligned the marks up, but not sure how the motor has not seized up running like this. The guy I bought it from told me it had been worked on by a local marine dealership, but denies anything major being done. I believe him about as much as our current Presidential administration though. I think this motor has had new heads put on along with a few other items. I replaced the ignition boxes myself. The compression ran 110 on one bank of cylinders, 115-120 on the other bank when I purchased it.
Current compression
All cylinders are now between 118 to 125. Number 2 was 118, 4-120, 6 120. #1 was 125, with 3 and 5 being 122. Thought those numbers were pretty good considering the compression is actually higher than when I bought it.
Did not successfully get the timing set to what the factory manual specs called for. The specs show 18 degrees BTDC at idle and 20 degrees max at max rpm. That just doesn't sound right at idle. Anyway, it runs best at about 6 degrees ATDC idle and advances to the 20 degrees BTDC by 2500 where timing is limited. The idle stabilization box didn't change anything whether hooked up or not. It appears to be recently replaced. Probably part of the 3000 engine work the previous owner claims he had completed prior to purchase. All other linkage fell into spec quite nicely and with exception of the oil pump linkage, was fairly close. I took it out on the water yesterday and it runs great above 1000RPM.
Under 1000 RPM, the idle is inconsistent. I can set it at 750 in water in gear, and then next time I start it, it may fall to 600 in water in gear. Another thing I am having issues with is the return to idle position in the linkage. This just started and is the reason for me to start this whole process. Sometimes when I return the throttle/gear selector at the helm to N, the RPMs remain at 1200. Looking at the throttle arm on the side of the engine shows the arm is not on the idle stop screw and must be physically pushed back. I can also jiggle the helm control and get it to return to idle sometimes. I removed the helm control and inspected and lubed it. It doesn't appear to have any abnormal wear, but the throttle cable does move back and forth about 10mm when jiggled. Could not find a reason why it would do this, but doesn't seem right.
Any comments are welcome. Learning this engine and want to know it pretty well. I have been taking things apart and figuring out how they work since I was two. Some things didn't get put back together quite right, but I end up fixing a lot more than I tear up. LOL.
One thing I found was pretty startling to me. Going through the process of lining everything up in the throttle linkage, I found the injection pump linkage very odd. When at full throttle, I noticed the linkage was binding severely and rubbing the fuel evaporator canister or fuel bowl and thought to myself, "this can't be right". I checked the alignment marks and there was no way that was right. What I figured out was the linkage had at some point flipped 180 degrees and was now going counterclockwise at full throttle instead of clockwise like it is designed. I corrected it and aligned the marks up, but not sure how the motor has not seized up running like this. The guy I bought it from told me it had been worked on by a local marine dealership, but denies anything major being done. I believe him about as much as our current Presidential administration though. I think this motor has had new heads put on along with a few other items. I replaced the ignition boxes myself. The compression ran 110 on one bank of cylinders, 115-120 on the other bank when I purchased it.
Current compression
All cylinders are now between 118 to 125. Number 2 was 118, 4-120, 6 120. #1 was 125, with 3 and 5 being 122. Thought those numbers were pretty good considering the compression is actually higher than when I bought it.
Did not successfully get the timing set to what the factory manual specs called for. The specs show 18 degrees BTDC at idle and 20 degrees max at max rpm. That just doesn't sound right at idle. Anyway, it runs best at about 6 degrees ATDC idle and advances to the 20 degrees BTDC by 2500 where timing is limited. The idle stabilization box didn't change anything whether hooked up or not. It appears to be recently replaced. Probably part of the 3000 engine work the previous owner claims he had completed prior to purchase. All other linkage fell into spec quite nicely and with exception of the oil pump linkage, was fairly close. I took it out on the water yesterday and it runs great above 1000RPM.
Under 1000 RPM, the idle is inconsistent. I can set it at 750 in water in gear, and then next time I start it, it may fall to 600 in water in gear. Another thing I am having issues with is the return to idle position in the linkage. This just started and is the reason for me to start this whole process. Sometimes when I return the throttle/gear selector at the helm to N, the RPMs remain at 1200. Looking at the throttle arm on the side of the engine shows the arm is not on the idle stop screw and must be physically pushed back. I can also jiggle the helm control and get it to return to idle sometimes. I removed the helm control and inspected and lubed it. It doesn't appear to have any abnormal wear, but the throttle cable does move back and forth about 10mm when jiggled. Could not find a reason why it would do this, but doesn't seem right.
Any comments are welcome. Learning this engine and want to know it pretty well. I have been taking things apart and figuring out how they work since I was two. Some things didn't get put back together quite right, but I end up fixing a lot more than I tear up. LOL.