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TOPIC: 1978 v1500 project revisited

1978 v1500 project revisited 4 years 2 months ago #120502

Progress to date; nil on boat, but i did finish my furnace and have had a relatively cozy winter. :)

Ok. I'm very conflicted on this motor. I do not own a few key items (engine hoist/crane), being number 1
#2 I have very limited dry shop space
#3 engine is still stuck in "trailer" position (I have the quicksilver deluxe controls with the trailer button towards the bow up/down buttons on throttle lever and key that sticks out towards port/driver)

Now that I'm done whining, I have a need for further guidance and will happily sort through opinions as well.

My engine is 1978 v1500 black max ser # 5024309
I feel like I should at least go through the basics with this engine and see if there is hope. It is in decent cosmetic shape; there doesn't seem to be any "frost creep" down in the prop/lower unit joint, prop spins by hand, lower unit still had oil in it.
Since it is stuck in the trailer position, can I ignore the tilt/trim issues and at least get the engine off of the boat so I can get the cowl off and get my hands dirty? With everything (control and steering) still connected about how much can I lift an engine? Enough to get it completely disconnected I hope.

I did get myself a factory manual off of that auction site part # c-90-89165 Is there a different one I should hunt down? I would love to get a factory parts book.

If the engine proves viable, where do i even start with the trim/tilt? With a battery hooked up, there is a signal getting back to the motor from the controls, but I have no idea if the system is cycling any fluid. Is there one point at which i can disconnect the line/lines and prime system to check for results? Feel free to kick this trim/tilt question back and/or over to a different forum as well.
Are there any real basic pros/cons to these v6 Mercs? as opposed to the late 70's inline options? There are a couple of I6 115's for sale right now within an hour of me that are listed as "good runners."
My engine is a 2.0 liter right?
does this darned thing have oil injection?
This site is awesome, i greatly appreciate the knowledge here, and thanks again for the couple of replies to my other post (78 fiberform runabout project).
Also, are there any books about Mercury outboard history? or a deccent book on Marine wiring?
Lastly, should I just nag my head and go buy a harbor freight engine hoist?
Thanks, Mike.

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Re:1978 v1500 project revisited 4 years 2 months ago #120516

im sure others with more experience will chime in.. but there should be a bleed screw somewhere on the side of the trim and tilt unit.. that you can loosen and tilt the motor down by hand if the trim pump isn't working.. that will atleast get you tilted down to get started on what ever you need to do on the motor..

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Re:1978 v1500 project revisited 4 years 2 months ago #120537

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I believe the v-6 mercs were not oil injected until the brown striped 1984. I had a 1983 v-6 200 that was NOT oil injected and now have a 1987 v-6 200 that IS oil injected. Some people out there don't rely on any oil injection and just mix anyway. I also believe merc was still rating horse power at the crank shaft until about 1983...because when I was ready to by the '83, they no longer had the 225 and 200 was biggest...and I believe that someone told me that is when they started rating horsepower at the prop-shaft like OMC had already done...so a I-6 115 built after '83 is 115 at the shaft, and a 150 V-6 built before '83 is only 150 at the crankshaft and would be less if rated at the prop...I do not know how much is lost, but it is less that 150 at the prop. I have had good luck with my motors, but all are treated differently. Mechanics, please chime in and correct anything here I might have gotten wrong or add to this. Likely they will say to do the compression check and leak down to see what kind of health your motor is in. They will also know what compression numbers to look for and what is ok or not.
Best luck on the rest...my knowledge is limited to what I had as I am NOT a mechanic.

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Re:1978 v1500 project revisited 4 years 2 months ago #120561

I'm pretty sure all the v-1500 Mercs originally had oil injection.
Your serial number group had it.
Even Mercury recommended a kit to eliminate the oil injection drive and other related components on the early v6, and strongly encouraged pre-mixing 50:1.
If your v-1500 still has an oil reserve tank above the carburetors and an oil pump gizmo on the lower port area of the front crankcase, with small hoses going between the reserve tank & this pump and eventually connecting to the fuel delivery hoses - it still has the oil injection.
If no oil tank and simply a piece that blocks off the hole in the crankcase for the original oil injection pump - then it has already been converted to pre-mix.
If this has not been done and you find that you have an otherwise good powerhead - I would strongly recommend purchasing the kit to convert to pre-mix.
Compressions on the v6 aren't necessarily as high as an inline-6, but should be at least 110+ and within a few PSI of each other.

The Power Trim for these v6s appear to have a pressure relief on the starboard side, in a hole in the transom clamp.
Item #12 in the parts break-down.
It is a black plastic fitting that has a straight slot for a large screw-driver, and some have a hex for a socket.
The problem is that the screw-driver slot or hex on this fitting is easily stripped or broken - rendering it unserviceable - if some fruit-loop put it in too tight the last time it was used.
If you are fortunate enough to get it to unscrew, back it out until it feels free of pressure - or clear out of the unit won't hurt anything.
If it is already thrashed - just post that issue and I'll explain the solution.
Then you should be able to manually raise and lower the beast.
If not,...Perhaps the tilt tube is seized and creating the whole problem??? Typical on salty dogs, but not on fresh water Mercs.

If you want to simply by-pass the solenoid(s) and hot-wire the power trim to see if it works,...Don't back out the pressure relief.

Disconnect the large Blue wire from the trim solenoid coming from the power trim motor, dis-connect the large Green wire coming from the power trim motor, and disconnect the large Black wire at the solenoid coming from the power trim motor.
By "large wire" I mean the #10 size wires.
Using jumper wires (or jumper cables are best),...Connect the Black wire to the battery (-) and the Green wire to Battery (+).
The trim motor should activate and if the system is full of oil the Merc should begin trimming Down. (be sure that a manual tilt lock device that holds the Merc in the tilted up position is not engaged)
If the Merc trims Down and you want to test for UP,...Black to battery (-) and Blue to battery (+).
If when attempting this test to trim UP or DOWN you simply get a spark, or click, and the jump wires get hot - or nothing happens - the trim motor is probably toasted.

NOTE: I doubt that a '78 v1500 would have a power trim pump that only has (2) wires - a Blue & a Green,...But if it does then it uses relays instead of solenoids, and equally important - on a (2) wire trim motor when temporarily hot-wiring it to test the system, to make the trim go UP, you hold the Green wire to battery (-) and touch the Blue wire to battery (+). To trim down, simply reverse these (2) wires.

IMHO,...If you are planning on doing the work and maintenance on this beast,...The HarborFreight portable engine hoist is a must have unless you are the Incredible Hulk, or Superman.

The book "Iron Fist" or maybe 'The Iron Fist" is a pretty decent coverage of the history behind Mercury Outboards.

When you are ready to undergo wiring upgrades on the v6, just post and one of us will post a relative wiring diagram, and answer any related questions. In 1978, Mercury wire colors were unique, but a few years later Merc stepped up to the plate and went to 'industry standardized' wire color codes. Consequently wiring the older Mercs - which had a variety of wire colors doing different assignments can be confusing and risky business that can smoke a lot of spendy components.

With everything still connected - steering cable, control cables, wiring harness, etc,...It is pretty difficult to move the beast up and away from the transom enough to attempt trouble-shooting or repairs on the PT.
I find it is easier to simply loosen the transom mounting bolts, and remove the starboard transom clamp assembly to access the power trim parts aft of the transom. You may not need to do this though, as you should trouble-shoot the pump motor & its solenoid(s) in the boat first.

doc F

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Re:1978 v1500 project revisited 4 years 2 months ago #120603

As I lived through when these were new (and my family being a Mercury dealership for 50+ years) and installing them, no, they were not oil injected, as that feature was not offered until 1984. They are indeed 2 liters (122 cubic inches). I would recommend the use of a hoist, and lift with a thread-in ring into the flywheel center. I would have to find where I hid my factory manual to jog my memory, but if you are going to remove it from the boat anyhow, you are going to need to disconnect the two power trim hoses, so that should allow it to tilt down. Being tilted-up does allow access to disconnecting the two short hydraulic hoses to each lower bolt (one hose to one bolt) on the outside (there are also two hoses on the inside from the pump to the opposite side of the bolts, and the bolts do differ from one another, I seem to think I remember). Note that if the two hollow lower (outboard attaching) stainless bolts were utilized, great care must be shown when unthreading the stainless lock nuts, or they will seize. We found the use of STP to work well when wrenching by hand. Do NOT use an air or electric wrench however, as heat builds to fast. The STP and care is even more important when installing the nuts to bolt the outboard on. There is a small manual release valve on the control valve portion of the power trim pump (these originally had a somewhat similar looking pump unit to a Mercruiser or in-line), but unlike an in-line's knurled knob release valve, it is like a 5/16" short round shaft with a roll pin through the end (the control valve is busier, as there is an electric solenoid present). I can't presently remember which way to turn for release, but clockwise would be my first guess. I would simply use some pliers to try to turn it, without being quite forceful. Once it does turn, do turn it until it stops to fully open the fluid passage. If the pump assembly was replaced for some reason in the past, it could have a different design pump assembly than described above (as seen to 1980-83 models).

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Re:1978 v1500 project revisited 4 years 2 months ago #120620

I must bow to Joe on this one. I thought I was looking in the right serial group on the v-1500, but I wasn't in respects to the PT.

I still haven't found a parts break-down on line that doesn't show an oil injection pump and related parts for the v-1500, but Joe has far more experience with the v-6 than I ever will.
Sorry guys - I'll go sit in the corner now.
doc F

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Re:1978 v1500 project revisited 4 years 2 months ago #120639

Hello All.
Thank you very much for taking the time to reply. The weather here in Seattle has been typically random and wet of late, so I'm going to go and get myself a little pop-up canopy thing to ease the outdoor work.

it seems like the Merc manual (90-89165) I have may be one year earlier than I need. So I found a 90-86133 today and ordered that.

Since I always have access to scrap and leftover lumber I thought about building a "knockdown" gantry and buying a chain hoist since I really do not have the space to store a cherry picker, although that would end up taking time to fabricate so... the Harbor freight tractor beam is getting stronger.

The part number my manual calls for for the lifting eye is c-91-75132 has this been replaced a couple of times? Is 90-904551 the current correct number?

It looks like my control assembly is a 12 pin. It is in good shape except that the chrome is peeling off of the throttle lever and looks a bit shabby. Would any other controls be a plug and play option? I would need to look for a 12 pin for sure correct?

There used to be a quicksilver steering option that i really like the look of; it had the 3 chrome spokes with holes, and some type of resin/plastic wood looking "wheel." Are these rare? There is one on ebay today, but it ends in a couple of hours, and there is separation in the wheel, and missing center cap. I may just grab it.

I will be sure to post pictures as I get into this further. i definitely don't have a problem using/making pre-mix, as I've dealt with a lot of 2-cycle lawn equipment. Thank you guys for jumping ahead and answering what would have been a later question regarding bypassing or abandoning the oil injection if it was there.

Doc; how far from Seattle are you, and what is your admission fee for being allowed into the operating room to drool? I can bring a mop.

Thank you all again, and I'm hoping to start making progress.

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Re:1978 v1500 project revisited 4 years 2 months ago #120646

The lifting eye tool is actually 91-904551, not 90-904551, and there are several on eBay to chose from.
There is also some extra tool parts that show up in some of the 91-904551 auctions for popping off the flywheels. A handy tool to have if you're going to be doing things at home.

"Doc; how far from Seattle are you, and what is your admission fee for being allowed into the operating room to drool? I can bring a mop."

No entrance fee required.
I'm in Shelton 98584, about 1.5 hours via I-5 and SR101.

Can you post a picture of the 12 pin connector?? Sounds like an I/O plug, but I dunno???
Maybe Joe P Jr knows???

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Re:1978 v1500 project revisited 4 years 2 months ago #120658

The 12-pin wiring harness plug was only a 1976-1979 Mercury V6 only arrangement. There would be some options for address your issues. Write me at This email address is being protected from spambots. You need JavaScript enabled to view it. if interested, and I will discuss them in depth.

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E. Carl Kiekhaefer (Mercury Founder) & Joe Poole Sr. @ 1964 Mercury Dealer Meeting

Re:1978 v1500 project revisited 9 months 1 week ago #140784

Man how time flies!
Joe Poole, It's been a while, but thank you very much for the replies here, the time on the phone, and the first order of parts. I really appreciate it.
I did buy the HF folding engine hoist.
I also bought a 1980 v1500 parts motor complete with tillt/trim, but minus controls. The main reason was to get the updated carbs as parts for the '78 carbs are either super rare or simply nla (I can't remember which),
My intended home for the engine is up on stands, and the trailer project is parked on my patio. We are thinking of moving, and nothing motivates a guy to get things done like thoughts of how to move a boat without a trailer and/or what to do with an immobile trailer.
My main sticking points with the engine work were these;
Can I essentially swap transom mounts and tilt/trim systems between these two engines? The system on the 1980 is much simpler, and it looks like the dimension s of the bolts (I completely forgot reference photos for this), are the same. What I think I have in mind is the "bottom yoke" #8658081 and the similar part at the top. 4 bolts total I believe. Center to center spacing between the two engines looked the same, and height looked same as well.
concern number 2 is/was the condition of the '78 lower unit when I pulled it and started prepping for updates. There was a lot of "debris" in there, and when I pulled the water pump housing bae out there was a lot of blue gasket maker type crap down there.
I would like to simply use the '80 lower, but there are subtle differences such as "connector assembly" 22-85822a1 which looks like a section of windshield washer tubing. The '78 does not have this.
Also, it seems like the two drive shafts are slightly different at the top.
Anyway, I'm anxious to finally make some real progress on this thing, hoping someone may still be scanning this very old thread.

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Re:1978 v1500 project revisited 9 months 1 week ago #140785

Doc, I forgot to say thanks to you as well.
Also, after a bit of internet surfing, I see that my aforementioned "connector assembly" is directly related to the speedometer and that the '78 should also have one. What the heck? Also, when re-assembling, how does one make sure that thing finds its home?

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