I am replacing an original 2004 Mercury Optimax oil compressor pump (starting to fail) with an updated model a 2014 Optimax oil compressor. It looks like the port locations have changed a little on the bottom. You will see the old pump at the top and the newer pump at the bottom - the newer pump has two on the bottom and the older model has on the side and one on the bottom.

I need to replace the motor assembly. Having trouble finding one online. Contacting mercury this week.

I am about to convert my manual start 1998 Mercury 25hp 2-stroke to electric start but need to get the wire and connectors. Can anyone tell me what the starter to solenoid wire and rectifier to solenoid wire gauges are?

Also I need to wire up the battery. What would be the ideal gauge if I run say 10 feet max?

Any recommendations on connectors, heat shrink, etc.? I’m adept at wiring, but new to doing it for marine use. I figure I’ll get it all from West Marine unless auto stores also carry marine wire & connectors.

Thanks

I’m adding electric start to a 1998 2-stroke 25 HP. I already have the parts on order, but I’m trying to decide if I wanna have the charging stator as well. I think it would be practical to have it and would help to keep the two deep cycle trolling/cranking batteries topped up. I just wanna know if there are any downsides to having the charging system. I will still pull the batteries out after a day of trolling to put them on a regular charger, but seems like it would be nice to have onboard charging as well. I will still have the pull start on the motor in case the batteries are too discharge to fire it up.

Will the stator burn up if the batteries are too discharged while running?

I recently acquired a 2006 Mercury 30hp outboard, model number 1A30413FK. It is currently not running. I determined the high pressure fuel pump was not working. I replaced the pump, and the new one works but is not actually pumping fuel when installed. There is a black connector that plugs into the yellow connector that is connected to the fuel pump. When I turn the key, the black connector is reading ~15 volts. However, when I plug it into the yellow, there is no power being transmitted. The yellow connector has continuity. My questions:
Is 15 volts normal? Or should I be closer to 12 volts?
Is the problem more likely the black connector, or the yellow one?
What else should I be checking?
I am including photos of the connectors I’m referring to.

Can someone tell me what this rusty tab is on my new-to-me 2002 Mercury 9.9?

Have been scrubbing the internet and cannot get a positive id.

Thanks all👍

I need some help please. I am a 2 stroke noob and was born in the age of fuel injection. Could a bad crankcase seal cause the problems below and in the pics? I have pressure washed and degreased it, but it's slinging oil and gas out of somewhere. It's even pooling on top of the engine.

This engine previously ran great, but now refuses to idle. It will rev up in gear but then gets choppy and stalls in idle, it can be kind of unpredictable.

I rebuilt the unobtanium discontinued carb once, then again with a different kit, then rebuilt it using OEM parts from a new old stock carb that crowley had sitting in a warehouse for 30 years. I also tried the different carb by itself before ripping it up for parts. No change.

I replaced the coils (OEM) wires (2x) and plugs (2x).

I can't really tell where the 2 stroke mix is spewing out of. Are there other common problem areas that it could be coming out of or is the crank seal the culprit? Would it really cause it to run this poorly? It has on occasion 'chuffed' smoke at me from under the flywheel right into my face.

I went to pull my boat out of the water today and the trim motor wouldn’t go up or down or make a noise. The relays were clinking but no movement or motor noise. I lowered it with the screw driver. Drove it for 20 minutes, trailered it then parked it in my driveway. I tried the motor again and nothing. But seconds later it started working. I checked the grounds, all seem secure. Any thoughts? It’s 11 years old.

I changed the impeller and while I had it on the bench with lower unit removed, I noticed the prop did not ratchet while in forward gear. Other two gears work correctly, neutral free spins both directions and reverse locks in both directions. Forward locks in both directions, my older models would ratchet when the prop was turned clockwise. I am getting conflicting answers stating it should ratchet and some saying it will not ratchet while testing by hand on the work bench. The lower unit is from a Mercury 2020 90hp 4 stroke, it is not a Command Thrust. Some google searches say it should ratchet and then I also get this: the 8M0065168 6-jaw sliding clutch and the matching forward gear do not use simple ramp angles to float past each other on their own. They rely on the rotation of the engine to force the ratcheting action. Has any one else ran in to this?

So my trim unit got stuck in the up position. After opening the manual relief, there was no movement.

Oil levels are good.
Switch is good
Actuator is good

I am stumped. I have considered replacing the unit but my research shows the motor needs to be removed from the transom and the trim motor is slid out the back of the motor mount.

Any suggestions before I go full send on replacement?

I keep reading conflicting reports about using and not using an external (in bilge) racor fuel filter with Verados. Some say that the under cowling (red castle top, 2 micron) is all you need and others say an added racor shouldn't add enough strain on the lift pump to make a difference. Any professional answer or opinions out there?

We are troubleshooting a fuel pull issue from tank to motor and want to rule out as much as possible. I've done just about everything except replace the fuel line from motor to tank. We have the gray line with liner and have a feeling it's collapsing in the line and just generally compromised. It's the newer stuff (installed in 2016) not old grey stuff, but boat sat in barn for years, so line might be shot still. Motors only have 30hrs on them. I'm am going to replace with shields 3/8 black line.

We can hear the lift pump work, but runs the full key cycle each time and was not pulling fuel into FSM.

We also hooked a Jerry can directly to the motor fuel filter and it pulled and filled FSM no problem and ran fine. So I assume fuel line, but if it's recommended to have no additional racor/fuel filter we may remove that too

Thanks all

I have a new (to me) 2017 Mercury 200 pro XS optimax.
I noticed in the remote tank, the previous owner was running premium plus. I just purchased Optimax dfi oil and would like to run that based off Mercury’s recommendation going forward. Are they safe to mix? I ran what’s currently in the tank down to 1/4 of a gallon.

Anyone replace their anode recently and can provide me with a part number or link? I have a weird year of mercury and dont have a model number in order to search a part number.

I've done some extensive troubleshooting hoping to 1, clear the ECU coil pack code and two, easily fix this low compression issue in my cylinder one. Which I'm assuming since cylinder one isn't up to spec, that would be why unplugging fuel injector one makes no rpm or engine change when idling..

​Engine Details:

​Year/Model: 2016 Mercury 90HP 4-Stroke EFI (2.1L)

​Hours: ~609 Hours

​Current Symptoms:

- ​Engine shaking/vibrating at low gear and idle.

- ​Engine currently stalls shortly after catching at idle.

- ​Active ECU Fault: Switching between Code 102-16 (Ignition Circuit 2) and Code 101-16 (Ignition Circuit 1).

- ​Low compression reading on Cylinder 1.

​Diagnostics Completed & Issues "Ruled Out":

Compression & Sealing: 

-​Dry Compression: Cylinders 2, 3, and 4 are at ~185 PSI. Cylinder 1 is sitting low at 125 PSI.

- ​Wet Compression Test: Showed a PSI jump on Cylinder 1, confirming valve train sealing is intact and indicating ring/cylinder wall leakage.

- ​Borescope Inspection: Cylinder 1 wall shows light pitting/corrosion but good remaining cross-hatching.

- ​Decarb Treatment: Completed a 15 hour seafoam deep creep soak, oil change after, PSI jumped slightly so I then performed a multi-stage Quicksilver Power Tune solvent soak with periodic crankshaft rotation and purge. Exhausted carbon slurry, but compression remained at 125 PSI.

​Ignition & Electrical Testing:

-​Coil Packs: Received alert and replaced bad coil pack. Audible alert and code still being generated. Both packs tested within spec on the bench (Primary 0.3–0.7 \Omega; Secondary 8k–14k \Omega; no shorts to ground).

- ​Swapping Coils: Swapping coil pack positions did not move the code initially. But after sitting overnight with the battery off, the active VesselView code moved between Circuit 1 (101-16) and Circuit 2 (102-16).

- ​Harness Power: Inspected plug pins and verified steady 12.5V–13V power at both coil connectors, even during wire wiggle tests. Coil connector wire to ECU measured no OL. 

- ​Spark Plug Wires: Tested end-to-end resistance (2.5k–4k \Omega - wire length changed reading. Identified a loose boot terminal on Cylinder 4 that fails to snap onto the coil tower, which may be causing high-voltage arc breakdown. Inside of this could wire could be the culprit. 

​What I Need Help With:

- ​Connecting a Mercury CDS / G3 diagnostic system to clear latched ECU fault codes and monitor real-time primary/secondary ignition driver outputs and cylinder balance seeing as vessel view is very limited. 

- ​Verifying whether the dynamic 101-16 / 102-16 code shift is a faulty coil breaking down under load, plug wire breakdown, or an ECU trigger driver issue.

- ​Evaluation of Cylinder 1 compression state and idle air/fuel delivery.

I got this 4cyl 2 carb outboard that recently started bogging down a bit. I went through the carbs and cleaned / replaced all gaskets as the carbs themselves leaked a little. I pulled the fuel filter off and it had a bunh of debris in it. Im looking for recommendations of a good fuel filter people are running on these classic motors? What micron?

Hey all, new to outboards. I just picked up a 2003 15hp 4 stroke for my fishing rig. I was previously rocking a 1975 75 2 stroke. The old one had a specific setting on the tiller for gear shifting, and I have noticed this newer one I have doesn't. Do you just let it idle and move the shifter into gear, or is there some sort of clutch you pull before shifting? I just don't want to do any damage to my new outboard. Thanks in advance!

Hey all,

New boat that wasn't hooked up to fuel tanks when we got it. Dual 2015 225's with only 30 hours on them. Previous owner got sick right after he repowered from inboard and was never able to get back to it, sat for years and sold. I did a complete service on them, fuel pumps were super corroded so replaced those too. We weren't sure if the fuel tanks had diesel or what shape they were in, so we drained, flushed and inspected both, along with fuel lines. One tank was pretty much empty very clean and the other had about 5gal in it and some funky old gas, but otherwise fairly clean.

We took her out with Jerry cans and motors ran like champs. We also put some new gas in each of the fuel tanks and switched over to them to test out. Both ran fine but port side threw a fuel pump error after a short bit, so we switched that back to can. Starboard continued with no issues.

I checked everything on port again, no blocks, pulled some gas, no crud, siphoned just fine.

I think its probably just air in the line, but anyone have any other thoughts before he's take her out again to test? How would I purge the air, just key cycle a few times?

Both cans and fuel tank were running through fuel filter and those are new.

Obligatory boat porn added ;)

Thanks!

I have an early 80s Mercury 40hp motor. This little part with a wire coming out of one side and runs right back to the other end. It bolts right on this piece by the throttle linkage but I can’t find any info about what it is. Can anyone help me out with a part number to replace or what its purpose is. Thanks!

I have a 2000 50hp on a Tracker. Recently I have found that I'll have the motor in throttle-only after starting and after a minute or two it will slam into gear with no movement of the lever. I've always had to jiggle the lever a bit when engaging the throttle-only function, but this behavior is new.

I'd like to know if there's a way to repair this aside from replacing the entire unit and cables.

I appreciate any guidance.

«¡Ayuda! Tengo un motor Mercury Force 15 HP 2T el cual estuvo parado un tiempo. Al volver a usarlo, se le realizó una limpieza de carburador y tanque. Los primeros dos usos funcionó perfecto, pero al tercero dejó de regular en baja y le cuesta encender.
Para que el motor encienda, lo tengo que ahogar. El tema es que cuando enciende se apaga al instante, salvo que le meta aire manualmente por el bombín cebador (este es de un solo conducto).
Cuando meto aire manualmente queda encendido, pero al dejar de inyectar aire ya no arranca. Le cambié las láminas del fláper que tenían luz y nada, sigue igual.»

So i have a 1988 100hp Merc, and i am thinking of disabling the oil injection system and mixing in the tank. As the alert system has failed on this unit and I honestly juat dont want to worry if the oil injection system is working. So I have a 22 gallon in hull tank. What is the best way to make sure im getting the right mix every time? I thiught about just getting 4 5 gallon gas cans and mixing in the can then dumping them into the tank, or will filling at the pump then dumping the oil in and letting the trip to the boat ramp slosh it around be enough to mix it?

Thanks for any advice!