30HP Merc EFI Four Stroke Wiring

AGENT 37

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I believe I have a Mercury-badged Tohatsu that I purchased used a couple weeks ago. I'm curious if I can get help identifying what connections need to be jumpered in order to get it to start for a test run on the stand without controls or a tiller before I spend a whole bunch of money getting the tiller with electric start.

Here's the engine info: Model Number: 1A3G312EK / Serial Number: OR568876 manufactured in 2013. The control harness connector on this motor is a 14 pin with female pins mounted on the upper starboard side of the power head, 10 of the pin receptacles are used. Pins and wire colors are:
A- RED
B -BLACK
D- BROWN / WHITE DASH
E- GREEN / WHITE
H- BLUE
J- PINK
K- BROWN / WHITE
L- YELLOW
M- WHITE
N- GREEN

I have a Yamaha /Merc manual that covers four strokes up to 2004 and that wire color coding doesn't match up. But the color coding aligns pretty close to what I see in my Nissan manual that covers two strokes up to 2000.

I have also ordered the Mercury factory service manual for this outboard, I'm just hoping somebody might be able to back me up on where I need to put jumpers to close a run circuit and pull the starter cord on this baby. Everything I checked out good on this motor, I just couldn't do a test run before buying. Thanks for any input!
 

pvanv

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As always, for Tohatsu OB products, year of manufacture is irrelevant. Tohatsu color codes are standard from year to year. Assuming you have a Remote motor, but no controls. Possibly a rebadged MFS30B, since it's more than 1 or 2 years old.

Red - 12v
Blk - Ground
Brn - Ign Kill when grounded
Grn - Start
Pnk and Sky Bl - Tilt/Trim
Yel and Wh - Tach

If you want to pull-start, nothing should need to be jumpered. Just pull. The EFI system is battery-less, getting its power from the alternator and charging system. If there is a stop switch with lanyard on the motor, that will kill the ignition when the clip is pulled or the button pushed.
 

AGENT 37

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Thanks Paul. You are correct, it is a remote motor and I currently do not have controls or cables. There is no safety lanyard or stop switch on the motor and there is no tilt and trim, it has a gas assisted tilt.

I put fresh fuel in it and tried pulling the cord when I was going over it prior to purchase and it did not fire. It did have spark and compression when I was checking things over though. I'm still hoping there is a missing run circuit (perhaps to power the fuel injectors) and it's incomplete due to the lack of a control harness. I guess I'll find out for sure after my service manual gets here and I can take a look at the wiring diagram.

So, there should be no need to hook up battery cables or a battery when running the MFS30B, correct?
 

pvanv

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Correct. You can use a battery, but it's not required. If the motor had been run out of fuel originally, having a battery would be good, as that will allow you to easily pressurize the fuel system, as opposed to pulling literally dozens and dozens of times.
 

AGENT 37

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Is it like other EFI motors where having the key "on" will run the fuel pump to pressurize the fuel rail without actually cranking the motor? If so, I wouldn't yet know how to close this circuit. There is only one red wire in the harness; the control wiring diagrams I see in my Nissan manual show making contact between two red leads in the ignition switch for the "on" position.
 

AGENT 37

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Ok, so I did a little messing around today with the motor. I hooked up 12VDC to the starter relay and put the NEG on a grounding point. I shorted the red and green pins at the control harness and got the starter to turn. I depressed the schrader valve at the top of the fuel rail to see if there was any fuel pressure and just got a minuscule puff of air out. After cranking the motor for a little while I did it again to see if it primed with fuel and nothing came out so I don't think the fuel pump ran.

I did a google search for "MFS30B Wiring Diagram" and came up with this:

https://www.manualslib.com/manual/1112952/Tohatsu-Mfs-25-B.html?page=301#manual

I note that there is a blue wire drawn coming out of the ignition switch and running to the outboard. It is not referenced in the switch condition drawing. If I am correct, this is an accessory or lighting circuit, correct? It is drawn to all the optional instruments as well. Is there any chance that this is also what powers the fuel pump when the key is turned to "on"?

I'm still waiting on my manual that's in the mail. (-:
 

pvanv

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Traditionally, Blue is for Choke (doesn't apply with non-carbureted motors). The switched meter lighting wire is also typically blue.
 

AGENT 37

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Here's the latest: Today I pulled the VST off, cleaned it out, and got the high pressure fuel pump turning with 12VDC. It was stiff to begin with but I was able to coax it to turn by gently working the impeller back and forth with a scribe prior to applying power. So there's a good chance it may not have been working previously.

I couldn't blow any air whatsoever through the fuel pressure regulator, still have no fuel pressure building on the fuel injector rail, and cant get the motor to fire up. What's the appropriate procedure to test the fuel pressure regulator? If it acts as a pressure relief valve, the system should still build pressure even if it is stuck closed, right?

My next plan is to check the high pressure filter for blockage, resistance check the injectors, and maybe apply 12VDC to the VST/HP Pump wiring to see if pressure builds and I can still hear the pump run.
 

pvanv

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Sounds like the motor was just shut down, without any winterization. Odds are the whole fuel system is gunked and stuck.
 

AGENT 37

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Yep, something is up. I put 12vdc to the HP pump today and got pressure to the rail. I pulled the fuel rail and injectors and could instantly see rust on them. All three resistance checked at 12 ohms but do not look good. I'm wondering if it was just the fuel system that got contaminated or if the whole motor was submerged at one point. I'm just going to have to keep picking my way through systems I guess...
 

AGENT 37

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Continuing on... I verified 14vdc at the VST electrical connector for the HP fuel pump and 14vdc at each fuel injector connector as the starter is pulled.

With the fuel rail removed from the intake manifold, no fuel was coming from the injectors. Holding each injector in my hand after removing them from the rail, I put 12vdc to the contacts to see if I could hear or feel them open and close and there was no sign of life on any of the three.

My third effort was to spray a small amount of fuel in the open fuel injector ports and pull the rope. She fired up for a few seconds!

Now, before I throw several hundred bucks towards new injectors I want to ask about compression: With the engine cold I was getting about 65psi on all three cylinders. After I lit the motor off I was able to get it up to 120-150psi on #1 and #2 by really yanking the rope/my shoulder but #3 doesn't get much above 95psi. In my buddy's Seloc manual, I've found compression specs of 40-60psi for some 15 and 20HP motors "with decompression". Should I expect those numbers to apply also to this motor? My understanding is that it has a compression release feature as well. The engine hasn't really been warmed up so I realize these numbers are pretty unreliable. I do not have leak down test equipment.
 

pvanv

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Decompression is in effect at slow speeds, say below 500 RPM, for easier pulling. At speeds above say 1000 RPM, you should have full compression. It would be good if you could actually get the motor to run and warm up, and then get compression numbers, but that may be difficult or impossible if none of the injectors are working. A leak-down test is very valuable, and the testers are not all that expensive; typically less than $200... but that is a lot of money if you will only use it once. It might be possible to borrow or rent one. At this point, you know that you have ignition, and you also know that your injectors are stuck. So, if you want it to run, you have no choice but to fix the injectors. But... MSRP is about $136 on each injector.
 

AGENT 37

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We're on the same page Paul. I've had plenty of opportunities where I would have liked to have the leak down test equipment. I get moved every few years though and am limited on my household goods weight so my inventory of shop equipment is restricted. Not that a leak down tester is all that heavy.... but I don't even get to own power tools or an air compressor. The tradeoff for having a boat and associated equipment I guess.

I have yet to rent test equipment that actually works... and my friends come to me for mechanical help so there's nobody to borrow from.

I've put in an offer on a set of used fuel injectors on ebay and have also found the new injectors sold by Mercury to be offered at a slightly lower price than the the Tohatsu ones... about $113 each. Surprising.
 

AGENT 37

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I went with a set of used injectors and a fuel rail for $200 including shipping, installed them yesterday and got the motor running. Now onto setting this motor up as a tiller steer, I placed an order for the Mercury tiller but am having second thoughts about it. I would have probably opted for whatever Tohatsu tiller option was available if I could find a complete kit to order. Everything I can find has the tiller broken down into all the individual parts, is there a simpler option than ordering every piece individually?
 

AGENT 37

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I purchased a set of used injectors and a fuel rail for $200 including shipping. After installing them yesterday the motor started up and was running pretty good.

My next goal is to set this motor up as a tiller steer. I initially placed an order for the Mercury tiller but cancelled it after having second thoughts about it. I think I'd rather go with the Tohatsu multi-function tiller if it will work. I'm having trouble finding a complete kit to order and I'm also not sure if I would need kit 3AHQ63000-0 (for B model) or 3NVQ63000-0 (for C model) Most websites I've looked at have the tiller broken down into all the individual parts and reference a shift lever that looks like it would be attached at on the starboard side of the lower cowl. Individually pricing out the parts for such a puzzle comes out to be around $350.

How likely is it that the Tohatsu multi function tiller kit will work for this outboard and what do I need to look at to verify that I in fact have a re-branded MFS30B?

Also, where would be the best place to order said tiller kit from online or over the phone?
 

pvanv

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Applicable models : Serial No. 25B/30B : MFS : 014361AB~
The New Multi-Tiller Handle Kit is available as an optional part and can be installed only for the serial numbers listed. THIS KIT WILL NOT WORK ON PREVIOUS MODELS. If installed on previous models, the result could be severe personal injury or death. Please read the installation manual carefully to install it by correctly.
The kit for the B model came out in 2013; The C model has a completely different cowl.
The correct model outboard has a strengthened steering shaft with a hole for the knock pin in the center. Also, the diameter of inner thread for stud bolts have increased to 10mm.
There isn't any way for me to determine the applicability of your merc based on serial number; It might be possible that Elvin at Solution One in Tampa might be able to determine whether you have the early or late version of the re-badged B model.
 
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AGENT 37

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I was reading up a bit, apparently the C model has a more "maintainer friendly" cowl. The oil filter is awkward to get a hand on with this motor and the engine has a factory tag with 2013 on it. I'm not sure what to look for regarding the "steering shaft with a hole for the knock pin in the center" I'll take a look at it again this weekend and see if I can pick up on this feature. I will also see what size bolts the steering arm is tapped for.

I took some pictures of the area around the rigging access cover on the lower cowl, the harness connector, and the shift and throttle mechanisms that I will try to get posted up.

One thing that stood out immediately is that the lower cowl has slots for securing the cylindrical shaped cable anchors of the Mercury style control cables. I'm not sure if the Tohatsu multi function tiller control cables run through this starboard run and secure in this spot with a different clamp or if this is a Mercury-specific lower cowl. I have the rigging instructions in my new Mercury manual and have also found instructions in a service bulletin (Bulletin No. 2006-14 / OEM No. 2006-04)
for replacing of parts associated with the Mercury tiller controls attributed to a "stuck throttle" condition some owners experienced. I have not seen any tiller rigging instructions for the Tohatsu yet though so it's hard to compare.
 

AGENT 37

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Here are those pictures.
 

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AGENT 37

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Update: I broke down and bought the Mercury tiller conversion kit. One of our local boat dealers here on Oahu was graciously willing to price match for the best deal I could find online. I got the kit and installed it today. I decided to install the co-pilot steering friction components first because I figured it would be easier to get done before bolting the tiller and carry handle in the way. The very first piece of hardware I went to install was the threaded bolt that goes into the swivel bracket with flat sides for the slotted copilot handle. It appears to be a size smaller than the threaded hole and I can put it in and pull it out without threading. The threads on both the bolt and the drilled hole in the swivel bracket are clean and undamaged, they are just mismatched and the bolt is too small to grip. Was there a change to a larger diameter special bolt for this application? All the other co-pilot hardware matches up and fits fine.

The bolt I'm referring to is item No.7: 3R3-62445-0

Aside from having no steering resistance, the controls operate smoothly. I will say that it was a serious pain in the butt to install though; the hardest part being the neutral safety switch (tight and awkward) The second tedious challenge was adjusting the simple cable for the starter lock just right, it has a tight tolerance and requires precision adjustment to have it work right. There was also no plastic nut included to secure the starter switch to the cowl, that's a simple fix though.

I'm ready to drop this thing in the water and go for a run... I will need a solution for the co-pilot steering though very soon. I also had to remove the trim tab/anode to get my turning point prop to clear. This was ans issue also on my old NS25C2 with this prop.
 
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