Rebuild - next steps

[andy.262]

So I'm finished assembling my 787 engine for my 97 SPX on the bench, and I believe the next thing for me to do is to put it back in the hull and align it. I have some questions as to what to do after that.

After I get it aligned and all the hoses and everything hooked back up, am I good to crank and start it on the trailer?
Anywhere I should put some extra lube or squirt some extra oil before trying to start it? (I already put the 30 weight oil in that plug in the crankcase, per the manual)
I was thinking of starting it without the drive-line hooked up at first, just to make sure the engine works. Any reason not to do that?

After all that, when I finally get to the water, do I have to do the entire engine break-in procedure all at once? Or can I split it across multiple days of riding?

Anything else to consider that I may have forgotten? Tests to perform before trying to start?

I'd hate to do something wrong now and ruin all the hard work I did to get to this point, so I'd rather do things right then do them quickly.

 

[mikidymac]

Did you pressure test the engine? That is the first thing you should do.
Then rebuild the carbs and fuel system then install and align the engine.

You can run it without the driveshaft and pump if you want just to see if it starts but it isn't necessary since even with the pump you shouldn't run it for very long out of the water.

You can not break int he engine on the hose so don't bother as it has to be under a load.

Run it at the ramp on the trailer to check for leaks before you take it out.

For break in you need to heat cycle the engine so you can do it over weeks or days. First full tank run 50:1 premix if you have oil injection and 32:1 if you only premix. For the first 1/2 of the first tank vary the throttle and stay about 1/3 throttle letting the engine run for 15 minutes then cool for 30 and repeat. At the second 1/2 of the first tank you can do the same but go up to 1/2 throttle. Then second full tank, no premix unless you don't have oil injection, first 1/2 same heat cycles up to 3/4 throttle and the last 1/2 of the second tank you can go wide open but never hold it wide open then you are done with break in.

 

[GGuillot]

On my builds I went all the way with driveline in pump, etc, because once you start it and set the idle, then briefly run it on the hose to check for leaks, you want to get it under load out on the water. As noted above you can't break it in on the hose.

Before dropping the engine in and aligning it, I'd connect the water line on the backside of the cylinders, and the rotary cavity oil line on that side as I'm dropping it in, once it's laid at 45 degrees it's more difficult to connect. Some people do it their way but I do it mine, but I sync the carbs on the rotary valve cover on the bench, then remove and install the rotary valve cover, oil injection lines, and oil pump as a unit, with it all primed from spinning it with a drill. It's assumed you rebuilt the carbs, pressure cked, verified pop off before you install them.

Then when I connect the oil tank feed line, I bleed the oil pump to remove any air. Then start setting the carbs on and adjust the throttle/choke. With the throttle plates closed completely, just as the idle screw touches, go 2 full turns in, then set slight slack on the throttle cable, you don't want the cable holding the idle. After that recheck the oil pump alignment. When all that's adjusted, install exhaust pieces. I install the back piece, then install the mid piece after applying the high temp copper RTV.

Connect the fuel lines to the carbs last, then install the flame arrestor and air box. Prime the fuel to the carbs by blowing in the return. Very first crank, I do a crank over with the spark plugs out to verify compression, then install them, choke it and crank to start, should be close on the idle, might need a slight tweak either way, you can get a tiny tac to verify, 3K on the trailer and 1500 on the water under load.

Once you get it set where it's holding a good idle run it on the hose briefly to verify leaks, then you're set to get on the water and break it it. I mix a 50:1 for the first couple tanks, take it easy the first tank, then on the second tank about half way through I'll start teasing WOT. I ran my skis with the HS needles set at 1/2 turn out for the first 20-30 hrs, then I tweaked them in to 1/8 out. That's where I run them today... Once it's broke in and you're turning 6700-6800 that's good for the carbed 787. On GPS I see 52-53 on the GTX and 55-56 on the GSX.

 

[andy.262]

Thats good detail guys, thanks! Nice tip on connecting those lines before dropping in the engine, I wouldn't have thought to do that.

Did you pressure test the engine? That is the first thing you should do.

By this do you mean compression test, leakdown test, or a different kind of test?

For the carbs and fuel system, I already replaced all the fuel lines and fuel selector, and I rebuilt the carbs about halfway through last season. Is there still a need to rebuild the carbs again given that I've done it so recently? I know my carbs were not the cause of the engine failure, and it was running fine on the stock screw settings. The engine failure was because the RAVE valves split apart and chunks of them were bouncing around in the cylinders.

 

[mikidymac]

You block off the intake and exhaust and put 8 psi in the pulse nipple to verify you have no air leaks that could seize an engine. A good engine will hold 8 psi for at least 10 minutes.

Your carbs should be fine then.

 

[andy.262]

You block off the intake and exhaust and put 8 psi in the pulse nipple to verify you have no air leaks that could seize an engine. A good engine will hold 8 psi for at least 10 minutes.

Your carbs should be fine then.

I will need to put on the exhaust manifold and RAVE valves for this test, right? Also, what's the best way to block the exhaust and intake? Only way I can think to do it is maybe some plastic wrap and rubber bands.

 

[WaarrEagle]

I am in a slightly different scenario, but I plan to run my rebuilt engine on the hose w/o the drive shaft/pump just to make sure it is working. I am doing this because there is quite a bit of $ and effort in reconditioning the "back end" (seals, carbon ring, pump oil, alignment tool, etc) and I do not want to part with that money until I have confidence that the motor will at least run. I also have a DI so do not have to worry about carbs/idle but it has more advanced electronics that I want to make sure are working.

 

[mikidymac]

RAVES and manifolds have to be on. You can make rubber covers for the intake and exhaust and sandwich them between the carb and headpipe to seal them off.

 

[andy.262]

I found leaks in the 2 circled spots where it's bubbling. What should I be checking for here? Crank seal? That gasket?

 

[mikidymac]

Gasket. But I would also replace the seal when you take the cover off.

 

[andy.262]

Prime the fuel to the carbs by blowing in the return.

I can prime the fuel to the carbs by blowing IN to the carbs via the RETURN (the line with the Y-fitting on it)? Maybe I misinterpreted what you mean by that, because that seems a little counter-intuitive. If that is indeed correct, how does that work?

 

[mikidymac]

No, you can blow into the tank vent. You want to put pressure into the fuel tank to push the fuel through the carbs.

If the lines are new you can blow into the return line that goes into the tank but it isn't as safe as I have had the pressure blow fuel back into my face before. Blowing into the tank vent is much safer.

 

[andy.262]

OHHHH that makes WAY more sense, I get it now!

My hoses are the black automotive fuel hoses that you can't see through, how will I know when it's primed? will it get harder to blow?

 

[mikidymac]

Fuel will come out of the black plastic Wye fitting that comes out of both carbs to the rear. As soon as fuel comes out of that fitting put the return hose back on it and clamp it down and you are primed.

 

[GGuillot]

No, you can blow into the tank vent. You want to put pressure into the fuel tank to push the fuel through the carbs.

If the lines are new you can blow into the return line that goes into the tank but it isn't as safe as I have had the pressure blow fuel back into my face before. Blowing into the tank vent is much safer.

With clear lines it's easy to see the flow as the fuel makes its way to the carbs, then I slip the return line back on the Y fitting. I guess with black lines blowing in the return would be a little risky since you can't track where the fuel is so the blowing in the vent line is safer.

 

[mikidymac]

With clear lines it's easy to see the flow as the fuel makes its way to the carbs, then I slip the return line back on the Y fitting. I guess with black lines blowing in the return would be a little risky since you can't track where the fuel is so the blowing in the vent line is safer.

You are absolutely correct and one of the bad things about the black lines. On the other hand I have yet to see a clear line that lasts for more than a couple years without turning hard and brittle.

 

[GGuillot]

On the other hand I have yet to see a clear line that lasts for more than a couple years without turning hard and brittle.

I might have found some clear fuel line that's holding up, bought a 50ft spool of USA made tygon clear line. I installed on the GTX back in 2018, the GSX last year, is still soft and pliable, only slightly yellowed. But I'm keeping a close eye on it. If I get 5 seasons probably worth it, I intend to do a preventive replacement at that point and go through the carbs again while I'm at it.

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