first boat, need knowledge on mercury 1500

[bigreed91]

Hey guys, so I just bought my first boat. It's a sportcraft C-Gull with a mercury 1500. I'm an engineman in the navy so I have experience working on inboard ribs but this is my first boat. I've tried looking up some things on this motor but haven't found much. If anyone ha any basic info on the motor or things I should know about it, common problems with it, etc I'd love to here it. Also before I try getting it running I know I need what I believe would be called the motor wire harness, it's o the harness on the starboard side of the engine with the plug with wires going everywhere. (Mine don't go anywhere cause the wires are so degraded) Does anyone know where the best place to get one is and the best place to get parts for these old motors. The rest of the engine looks to be in great shape but I know looks can be deceiving. Any help is greatly appreciated.

 

[MH Hawker]

Re: first boat, need knowledge on mercury 1500

The motor serial number is the place to start.

 

[Chris1956]

Re: first boat, need knowledge on mercury 1500

A Merc 1500 is an inline six, with distributor ignition. The last year for them was 1977. Wiring harness may be had at lots of web sites. Surplusunlimited is one of those. Carb parts are avail lots of places.

 

[wired247]

Re: first boat, need knowledge on mercury 1500

black bear sporting goods is going to have your best pricing on CDI parts. CDI makes the aftermarket wiring harness for that motor.

Do a leak down test on it if you can. A compression test will be useful if you cant do a leak down test. Once you get the wiring taken care of you will have to deal with the carbs. If the loom is as degraded as you say it probably hasnt been started in years so the carbs will be gummed up and in serious need of cleaning and a rebuild. Those things run like absolute crap if the carbs arent tip top. PM me if you need a shop manual.

 

[oldandintheway]

Re: first boat, need knowledge on mercury 1500

Welcome to iboats.

Here is a link to FAQ on this site:
http://forums.iboats.com/engine-fre...kening-sleeping-outboard-boatbuoy-158086.html

 

[bigreed91]

Re: first boat, need knowledge on mercury 1500

Well I know it's an inline 6 with a distributor. Where is the serial number on the engine?

 

[wired247]

Re: first boat, need knowledge on mercury 1500

Its stamped on the starboard side. Doesnt matter much though. Its a 1500 and they made them from 73-78 without many changes other than slight cowling differences and some minor carb changes. Early '73 motors are ported a little high for good low end torque but most of the later 1500's are pretty much the same except the 1500XS which resemble the early 73's in their porting . CDI makes a bunch of electrical parts for them including complete distributors and switch boxes, wiring harnesses etc.

They have some issues. Hard to find a shop to bore the cylinders as they are blind bored from the front and they are awful getting those pistons back in. The reed setup flat sucks. They are about maxxed out for what you can do with a 1.6 liter crossflow ( Although I still think you can get more power out of a 1.6 Johnyrude ) but the 1500 with its ported piston was sort of a cross between a looper and a crossflow. They are somewhat lightweight but keep in mind that the published 295 lbs or whatever it is does not include the external trim pump and ram assemblies. Pistons are available. Get the early style high domes and run premium gas. New reed blocks unfortunately are not. Fiber reeds are. The carbs are a ***** adjust right as the transition circuit is nonexistent and they go right from idle to main circuit so you have to richen the idle circuit up quite a bit.

I had one on my boat for a little while . Didnt get much thrill out of it and it went away for a 2.5. Very distinctive chainsaw sound.

 

[Chris1956]

Re: first boat, need knowledge on mercury 1500

The Serial number should be between the clamp screws on the transom clamp. Wired is a bit cranky today, but he does make some accurate points. The 1500 is a bit of a thoroughbred. It is a bit harder to get her tuned to the max, but she has some real power in mid-range and top end. Bottom end power is a bit lacking.

On my speedboat, once the motor hit 3000 RPM out of the hole, she would be on plane and she would accelerate very-very quickly ( a couple of seconds) to 4500+ RPM. If you didn't start to ease back on the throttle at 3000RPM, speed would increase so fast, it would literally launch skiers out of their bindings. it would also scare heck out of the driver, if he wasn't expecting it.

I blew up my 1500, and now run a 2.0L 135HPV6. A lot more bottom end and about the same high end, but a lot more weight and very predictable performance.

 

[CharlieB]

Re: first boat, need knowledge on mercury 1500

WARNING: During a tune up it is temping to pop the distributor cap off and try to remove the rotor. DON'T The rotor is part of the shaft and is NOT removable without breaking it.

Timing and carb adjustment is critical to the performance of this motor. Somewhere in the 'sticky' posts at the top of this forum is buried a post writting by Clams tenino (if I spelt his last name correctly). Find it, follow his directions to the letter.

As previously mention, most two stroke carbs do not have much, if any, transition circuit so the idle mixture must be adjusted overly rich to provide the additional fuel necessary for crisp clean acceleration. Often times this is can be at least 1/8 turn fatter than 'Best Idle Speed'.

 

[eggs712]

Re: first boat, need knowledge on mercury 1500

Also, with today's fuels, I would set max advance timing on your 1500 to 21 or 20 degrees BTDC.

 

[wired247]

Re: first boat, need knowledge on mercury 1500

Only the first year or two of the high dome 1500's had 23 degrees as a standard setting. After that they dropped to 21 as the recommended setting. 21-22 degrees will run fine on 92 octane fuel with the 82 main jets. Do not lug those engines with too much of aprop. They need to be in the 5800-6000 range WOT which means 17-19 pitch prop for most purposes.

 

[bigreed91]

Re: first boat, need knowledge on mercury 1500

Lots of good info guys i really appreciate it. It's gonna be a while before i get to work on it, i was home on leave when i bought the boat. So i'm back to virginia till september. Then i'll be back there for good so it should be a fun winter project. I'm just trying to learn as much as possible while i can't work on it.

 

[bigreed91]

Finally an update: last week i completely rewired the starboard side wiring on the engine and replaced one plug wire that was chewed in half with an old ford wire. Got it turning over but wouldnt start, did some research and found out that the mercury switch was doin its job ( i had it trimmed up). Finally got it to start and it ran pretty good. So we took it down to the river ( couldnt stay to long or go to a lake cause it aint registered yet) anyways it topped out at a whopping 8mph lol the tach wasnt working so i have to chase that wiring next. But it does run so next since the second to last owner had said it lost compression im gonna do a compression test and also start a decarbing process. I'll get the compression readings then decarb it. Im hopeing its a carbon issue with stuck rings, not broken rings and scored walls. Anyways since the boat isnt registered i dont like taking it out on the water to run it at wot to decarb it. Can i seafoam it with the lower unit in water like i have it now and expect good results without a load on it? Thanks for all the help on this forum.

 

[Chris1956]

The spark plug wires are stranded stainless steel, so your old Ford wire is likely a bad idea, as it is likely a resistor wire made of powder.

After you check the compression, put a timing light on all cylinders to see if you have spark. Those old plug wires can arc to ground. Test them for resistance. Resistance should be zero. BTW the plug wires UNSCREW from the distributor cap.

 

[bigreed91]

Thanks i had a timing light on each wire and they were all good, i didnt check resistance though. Either way i pulled all plugs yesterday and turned it over by hand, number 3 had absolutely no compression sucking or blowing. If i take the covers off the side of the block does it allow you to see the pistons? I would just like a visual at those rings. Its lookin like its in need of a rebuild though.

 

[Chris1956]

Yes. removal of the transfer covers will allow some inspection of the piston and cylinder. BTW - #3 piston is usually the one to break first, due to overheat or clogged carb.

 

[bigreed91]

When removing the carbs are they on a rack together or do they come off seperately? Im lookin at it like a carb'd motorcycle where they bolt up seperately but are linked together and have to be sync'd. Is it the same way on these outboards? I've started pricing parts, if the cylinder wall is ok and not in need of boring requiring an oversized piston is it ok to reuse the original pistons?

 

[Chris1956]

The carbs are separate, however, the fuel hoses tend to hold the carbs together, as do the two throttle plate connectors. In a nutshell....Disconnect electrical, remove the 6 bolts ( 4on rear of cowling support, 2 on top front cowling support), 3 smaller nuts on top of cowling support. Remove starter top bracket. Remove 6 bolts and three carb covers as an assembly. Now the carbs will come off separately. The top carb will need to be wiggled to get around the dristributor "finger" that opens the carbs.

The plastic throttle plate connectors are brittle, and the unbolt from the carb tops. The slotted hole in them serves to synch the throttle plates, so they all open at the same time.

Oversize and stock pistons can be mixed anyway you want. So if just #3 is bad, bore it oversize and install oversize piston. Put new std rings on the orig pistons. Now fix whatever caused the problem, or it will happen again. Rebuild all carbs, fuel pump, clean/replace fuel filters, rebuild waterpump, adjust link and synch.

 

[bigreed91]

Sounds pretty easy, i dont have a manual and my wife doesnt like spending money on my toys. But it seems pretty simple, this aint my first engine teardown just my first outboard teardown. Hopefully it just needs one new piston, all new rings, maybe some new plugs and wires and cap, and might as well get a new impeller too. Thanks for the help chris.

 

[Chris1956]

Wires($7 - $12+ ea), cap ($150?) and rotor are pretty expensive for that motor. Try to take care of them. Rotor is non-replaceable, as you need to buy the whole distributor shaft ($200+) and install it.

There is a downloadable service manual site (boatinfo.no). not sure if it has your model.