Seized 18hp fasttwin, 1967, where do i start???

[John the landlubber]

I bought this as a non runner. The flywheel won't turn and the pull cord is broken. The engine on the whole looks to be in very good condition. I get the impression engine sizure will be either blown pistons, briken con rods or seized bearings. I have removed the head and cant see anything obvious with the top of the pistons. So I assume I next have to look at the crankshaft end. Do I have to completely remove the powerhead assembly to get in the crankcase.

 

[jfm1]

Re: Seized 18hp fasttwin, 1967, where do i start???

try removing the lower unit, maybe the gears are frozen

 

[DHPMARINE]

Re: Seized 18hp fasttwin, 1967, where do i start???

Then,yes you need to pull the powerhead to split the crankcase.<br /><br />DHP

 

[Solittle]

Re: Seized 18hp fasttwin, 1967, where do i start???

Before you do that you might put a couple of tablespoons of Marvel Mystery oil in the cyls & let it sit for a couple of days. Put a socket wrench on the top of the crank & see if you can free it. MM oil will work wonders - - - sometimes.

 

[gatorred]

Re: Seized 18hp fasttwin, 1967, where do i start???

two cycle oil,kero,dextron 3 all work's well to free up stuck piston's I mix it to gather put it in sparkplug's go let it sit day or so if it dose not free up then look at lower unit for stuck if it's two part case just spilt case drain first if rusty stuff it's there.

 

[itstippy]

Re: Seized 18hp fasttwin, 1967, where do i start???

Why do you figure blown pistons, broken con rods or seized bearings? Did you get to talk to the guy who was running it when it seized? <br />You may be lucky and it's seized from age/inactivity - "storage seized". The scenario is that it got out of tune and hard to start. The owner yanked and yanked at the cord trying to start the motor until his ribs hurt and the cord broke. So he put the motor in a corner of the garage to "work on later". Twenty years ago. Now the rings are stuck to the cylinder walls and you just gotta free them, check compression, tune her up with a carb kit and a new impeller, and go fishing. That's what the guys are getting at with pouring penetrants into the plug holes, letting it soak, then turning the crank with a socket wrench on the flywheel nut. That's great advice. If you can free it up you can often fix them without pulling the powerhead or splitting the case. If it's storage seized.<br />Now if it was running when it seized that's a whole nuther matter. Then you can figure blown pistons, broken con rods or seized bearings. Definately start by pulling that lower unit and have a good look at the water pump impeller.

 

[Chinewalker]

Re: Seized 18hp fasttwin, 1967, where do i start???

I would highly recommend against running the motor if you should happen to unstick it without taking it apart. Unless it was absolutely simple and easy and you're sure nothing is wrong inside, you run the risk of having the motor grenade on you in short order. Could be minutes, could be hours, but if a motor is stuck, more than likely it has bearing issues which can lead to chattering, bearing wear and eventually failure. Even if the rings are the only thing that is stuck, usually they are also stuck in the ring grooves and you'd have lower than nominal compression. There are also usually ridges left in the cylinder wall when the rings stick, also leading to wear and compression loss. <br /> If you really want to spend the time getting the motor going again, spend a little more time and tear down the powerhead and do it right. Even if you don't find a bearing problem, you'll know and won't have to worry about it...<br /> Of course, this is assuming the problem isn't localized to the lower unit as suggested above...<br />- Scott

 

[John the landlubber]

Re: Seized 18hp fasttwin, 1967, where do i start???

Ok guys, took your advice. Put engine on floor with spark plugs facing upwards. Pourede 2-stroke oil into plug holes and let stand for a week or so. Went back and tried to turn over using a socket on floywheel nut. No Joy. Drained lower unit, but as soon as I opened drain plug some water ran out, followed by dodgy looking oil. Removed lower unit and found lots of bitty and reddy looking stuff around top of water pump. On top of this, tried turning her over with a socket on flywheel once lower unit was removed aqnd she still won't budge. Guess I'm in this for the long haul, lol. Where should I go from here???

 

[Chinewalker]

Re: Seized 18hp fasttwin, 1967, where do i start???

HI John,<br /> Right now you have a really complicated looking boat anchor. You've got a lower unit with water in it, and a powerhead that's stuck. Taking it apart won't hurt anything right now, as it's already in rough shape.<br /> Start tearing it down. Begin by using the midsection as a motor stand so you can remove the recoil, flywheel, ignition, cylinder head, carburetor, intake, etc. Once you get it down to a shortblock, remove the bolts and nuts that hold it to the midsection. Keep in mind that there is one bolt at the V of the powerhead base that is accessible from underneath. A long-reach 1/4" drive socket wrench with (if memory serves) a 3/8" socket should grab it.<br /> Then remove all bolts holding the crankcase together, keeping in mind that there are two under the intake reed plate. Use a flat punch to drive out the two alignment pins, pushing them FORWARD, as they are tapered. Once the pins, and all bolts are out, gently tap the front of the crankcase away from the block. Don't pry it, just tap it...<br /> At this point you'll likely see the cause of your stuck issues... and a manual would really be helpful if you wish to continue beyond that point.<br /> If you determine it's junk, keep an eye out for powerheads on eBay. Any of the 22-cube 18-25hp powerheads from the mid 1960s on up to the late 1970s should work.<br /><br />- Scott

 

[Solittle]

Re: Seized 18hp fasttwin, 1967, where do i start???

Lets see - - you got a 39 year old motor with water (& who knows what else at this point) in the gearcase and a frozen powerhead. Unless you have a love for fixin things for the love of fixin the answer here seems kinda obvious.