250 ox66 long block swap starts but won't stay running

[99yam40]

gas is not like Diesel and fuel oil it goes bad a lot sooner.
There is no way that I know to check it.
the tanks on a boat are vented,
so there are things that will evaporate and leave the fuel making it not as good as it should be


A high performance engine running old fuel (18 months and probably more) is not a good thing, but I have no way to prove it will hurt the motor.
But most high peformance motors are run with very good fuel to make sure there are not problems.

Good luck with the motors

[rodbolt17]

that's why them dang nascar bubbas run 2 to 4 yr old gas.
makes blow up faster.

[DBClubbs]

I understand the octane level decreases and hence potential for knock and the obvious lack in performance, and possibly some loss in lubrication. But for the 10 hour break in procedure I'm not looking for all out performance, the non-ethanol fuel around here is mid grade so I'll be adding 89 octane to "old" 87 octane, and I'll be adding oil to the fuel. So I really don't see why I can't run it. Granted if I had one of said "nascar bubbas" to donate 135 gallons of fuel to I would get rid of the stuff. I have asked around and do have some takers on the stuff but in 10 gallon increments. I'll fill up what I can around the house and I may be able to get rid of 50 gallons or so, the rest I'll have to burn through the yamahas.

Again thanks for the help, I'll keep you posted. My tilt/trim cylinder seals don't arrive until Tuesday and I have to rebuilt the helm pump on the tower this weekend because that too is leaking... Sitting for a couple years really degrades a boat; its taking me much longer than I expected to get this rig going.

Dave

[rodbolt17]

not particularly worried about octane, knocking will be detected by the knock sensor.
its designed to run on 87 octane and will run piss poor on fuels above 93 octane.

old gas tends to leave deposits on the piston skirts and sticks rings on two strokes due to how the fuel is delivered.
but its your motor.

remember,piston to wall clearance is about .0015. how much skirt deposits are allowed before clearance is .00000?

[DBClubbs]

Well thats a convincing reason... ill hold off on the breakin until i can pump all the gas out. I guess that will give me time to put the other long block on so i only have to do the breakin once.

Other than that my attempt to rebuild the seastar helm pump on the tower failed. I think the check valves are too pitted to work properly. So ill take the valve body of one of the other pumps i have.

I got all the new orings and seals for the tilt trim cylinders and the spanner wrench tool. I got all 4 trim caps loose then busted 6 of the screws in the tool trying to get the trim caps off so ill get more tomorrow and try again.

All the oil filters and the o2 harness came too. Now if i only had time to put it all together.
Plan is to get the helm done and the system bled before the weekend, then get the tilt trim units off during the day saturday so i can rebuild those in the evening. Im real close to finishing a restoration on a friends cj7 that has been taking up lots of time, but i may be done with that this weekend.

Ill post back with updates, thanks for the help so far

Dave

[DBClubbs]

While rebuilding the tilt trim units i found the lip seals in the top of the caps have a steel liner in it!!! So of course it has rusted and pitted itself into the aluminum and now i need new caps too not just new seals. Did i just get a mistake or has anyone else had steel in their cap seals too?

Dave

[DBClubbs]

The tilt ram didnt have a steel liner in its seal, but the trim seals are magnetic... thats fantastic. I cleaned up the bore best i could and put new seals in everything. At least if the trim seals leak thats an easy fix without having to take the whole unit off the bracket. Got one done tonight and hope to get the other done tomorrow night.

I picked up a 150 gallon aluminum tank today from a semi truck salvage yard for $95. Im goibg to douse it with degreaser best i can and flush it out. Ill build a quick cradle to get it high enough so i can gravity drain into 5 gallon cans through a filter of course. Once its on the cradle ill siphon the fuel out of the boat.

I decided to swap the port long block too so i can break them both in at once. The original port engine is running fine now, but since i have the other new block it makes since to swap them both at the same time. That means i have a good used OX 66 SSII 250 long block for sale... pm me if anyone is interested.

Dave

[DBClubbs]

I did a compression check on the original port motor tonight since im going to pull it off tomorrow. Heres what i got from cylinder #1 through #6: 104, 110, 107, 117, 98, 102. Other than fogging it anything i should do before i take it off in case i end up storing it for awhile. I took video of it running if anyone is interested...

Dave

[DBClubbs]

Pump about 156 gallons off the boat tonight. Still about 40 or so in the boat. It still smells good so ill be running the juice through the wifes jeep. Almost done with the powerhead swaps. Hard to find time to work on it, but plan is to go start breakin on labor day.