1974 20' sceptre transom replacement and i/o to outboard bracket conversion

[flyingfrizzle]

Now that I have gotten the main parts on the block and it is shut up to keep the dust out I started working on the more tedious items like the mechanical fuel pump, the bleeder lines, throttle linkage, thermostats, and other small items that need to go on before the electrical. I decided not to use the factory oil injection due to the high fail rate of the crank gears. They are plastic and will striping out easy but I did leave the gear on the crank so that it would take up space in the block. This will keep the air flow the same on that cylinder. Some people remove the gear being it is not used but that is a big mistake unless you epoxy the dead space in that passage way. The extra air space will slow down the velocity of that cylinder and it will pull less air threw the crank case. It creates an imbalance between cylinder banks and also, worse case, will lean that hole out causing a possible burnt piston. The more material you remove from the crank case the slower the air flow is and that kills power. On the race motor I have block stuffers that bolts into the bottom of the bores just to take up air space just to maximize the velocity. You would be surprised just how much power is gained by "stuffing the block". You would think the more open the better flow you get but it don't work that way in a 2 stroke. There is a plug kit that goes in place of the oil pump shaft and the small gear that inserts into the block. It will hold the brass bushing in place that is inside the block and keep it from coming out as well as cap off the hole on the out side of the block and also filling in the lost volume that the removed shaft took away. Next I install the trigger then stator and hook up the advance arm. I get the fly wheel installed, it is keyed so you cant clock it but one way. The starter gets mounted. I mount the rear cdm bracket and cdms( kinda like coils). Pop on the plug wires and make sure all the grounds are attached well and clean. Most of the older mercurys ran coils and switch boxes but in 2000/2001 they went to the cdm system and got away from the switch boxes. The cdms make for a much smoother and better controlled motor. Most of the race motors still run the switch boxes due to they rev 10,000rpm plus and the cdms will only support up to 8000/9000rpm then start breaking down. Most of the race motors in the 2000s came with cdms but the guys that turn them hard swap back to the switch box/coil ignition. For a river motor I would rather have the cdm set up but the other motors for my race hull will be getting the old style system even tho I wont turn it past 9000. After the ignition bracket is mounted on the rear of the motor the brackert fror the voltage regulators goes onto the side of the block. Then the start solenoid and trim relays go onto the bracket as well. I installed the wiring harness and started plugging every thing back in. I numbered everything with label tags before I unplugged it just so I knew where to go back with it. Most plugs are different and wont cross but I numbered it to make it easier. There are tons of little ground wires that go below the starter, make sure they are clean and all hooked up cause one left off and that could cause some major issues. Next up is the front fuel management system. I install the efi laser style injection and the water separator bracket with filter. It was cleaned very well including flow testing the injectors. You can send them off or you can make a home made rig to test them. Mercury sells a injector test box that will pulse the injectors at different rmp bands and you can set them up into a collection bottle and use a timer to run a time test run. As long as they have a nice even spray pattern and the fluid level is the same per the others you are good to go. If one is bad you will know right away by the bad pattern or the lack of fluid it puts out. If its stopped up you can back flush it with throttle body cleaner and wash out the crud in it till you get the even spray pattern and correct flow sometimes. My buddie has a set up with 6 corona bottles that collects the injector spray at the same time and can run all 6 together. I looks just like a back yard version of the real thing, instead of test tubes it has beer bottles. Works well for a red neck injector flow bench. Last thing you want is a bad stopped up injector smoking a piston in your new rebuilt motor. So once the injection set up is on the front of the adapter plate, all the rest of the throttle linkage can be hooked up and tested for wide open throttle. The gear shift/throttle slider can be bolted up. The rest of the wire harness plugged in. The two little black boxes (knock sensor) and (oil injection) warning modules only the one will go on. Now I bolt the VST tank to the motor. It gets cleaned well and usually there is varnish in the tank but this one was really clean due to the low hrs. The fuel lines to the laser unit get hooked up and also to the mechanical pump to the tank. The electric fuel pump wires go on. The studs and ring terminals are different sizes to keep from it getting hooked up backwards and reverse flow. The bottom oil feed hole gets plugged due to the premix. Next I install the Brucato ECU on the front of the motor. This is an after market ecu that will give me some different fuel curves and some adjustability of the fuel air mixture. I can hook it to my lap top and see tons of info as well as easily adjust it. The factor units are great till you start modifying the motors then you will need to reset the curves. I could of got by with the factor unit on this lightly modded motor but I will get a better tune with this one plus pick up some power. I spend some time doing a one over to make sure all the bleeder lines go to the right spot cause there is a ton of them. If you leave them off it can cause an ruff idle from fuel puddling in the intake or worse case leave off the line to the bottom bearing it could cause it to lock up from no oil. I try to make sure all the wiring is in place and the plugs are tight and secure. All the fuel lines get special tie wraps that are 50# rated and also have a special tab for full 360 degree seal. I see a lot of standard tie wraps on these outboards were they were replaced incorrectly with house hold type. They only seal part of the way around and don't get the section by the head where the right ones have a tab that catches contact all the way around. Now comes the fun part, getting this heavy thing lifted up and placed on the midsection.

[flyingfrizzle]

If you made it threw the long diarrhea of a post previous to this one you may of caught the part about using the correct tie wraps to secure the fuel, vent, drain and oil lines. The mercury oem ones are quite pricey so I found a set on McMaster Carr site and ordered them at a lot cheaper rate. If you guys need any while hooking up lines you should be able to get the PT# of the bag below. The other picture shows the difference in the two. The curved base of the correct ones will give you that 360 degree seal where the standard ones fall short. I know some of you may just use hose clams or worm clamps but if you would like to go back with the factory type ties here is a way to get them a much more reasonable price.

[gofastsandman]

Looking good.

Any estimate of prop hp on the race motahs?

[flyingfrizzle]

Originally Posted by gofastsandman

Looking good.

Any estimate of prop hp on the race motahs?

I am hope to see 250-270ish to the props, a factory promax 225 (which is what those are basically) makes 245 to the crank. Mine will have the SVS intake systems, port work, lighter fly wheels, higher compression, block stuffers, cut reed cages, and a few other tricks so I feel like getting the extra 25-30 hp wont be too hard. Tommy told me he can make 280-300 easily, he said any thing past that is hard to make and will take spinning it past 8000rpm. Like to be able to run high test ethanol free spiked with cam 2 and keep them some what more reliable so nothing to crazy. Match that pair on the light 27' hull and betta hold on...... It will be a ride to say the least!

[flyingfrizzle]

Got the power head on the midsection and got all the rigging done. Checked to make sure she trimmed up all the way with out hitting. All the way up she is about an inch and a half to two inches from the transom crown. I put on a cowl from another motor I had so I can paint the one that belongs with this outboard. Plans are a fresh coat of mercury black and new pro xs decals in matching hull blue. After getting it in the water it is sitting on her lines much nicer with the lighter outboard. The swim platform is much higher out of the water. I also have 20 gallons of double oil premix gas in the front of the tank coffin so it will balance even better once I add more fuel. Went 2 hours at idle to 2500 for ring break in at variable RPMs at 25:1 premix ratio. Then went 2 hours between 2000-3200 rpm. Changed the premix to 32:1 due to the plugs were starting to look slightly fowled from the extra oil then ran it 4 more hours between 1500-4500 variable rmp. It is not good to seat rings or break in a motor at a steady rpm. You should keep changing it up and down at different rates at least for the first 6-8 hours till everything gets broke in. Once I got some time on it I started to run it briefly at higher rpms for short periods. The second day out I ran it 30 miles or so and varied rpms and ran it up to 5000-6000 for brief burst. Even took it up to 7000 a few times just because I couldn't help myself. The acceleration with the low pitch prop was awesome. Cant wait to prop it up higher and see what it will really do. The low speed planning seemed to fall off around 18 mph so hopefully when I get more fuel wait in the front it will help with that. Overall the balance going from a heavy 225 3.0 to the lighter 200 2.5 and moving the fuel forward and getting the rear mounted oil tank gone seemed to make a day and night difference. I still have a rear mounted battery that needs to go up front and that will help too. I am really surprised how these hulls respond to balance and weight distribution. A little weight makes a big difference. I was able to raise the motor all the way up where the trim was maxed and surfacing the prop and zero porpoise. Before I would get a little bit if the motor was all the way up and it needed a little lower trim to keep it tracking straight. No tabs yet but Im sure they would really help the lower planning speeds. Over all going to the lighter outboard was a great move. Not to mention I will have more power and better fuel economy now as well. Great trade off.