Repair or Replace?

[paulutions]

New to outboard motors and I bought a sailboat that has a bad 1993 6hp, 2 stroke long shaft motor. I do not know whether I should fix it or buy a new one, but I thought if it would be cheaper to fix myself, I'd give it a try. It runs for a bit and then dies. I actually narrowed that down to a bad CDI. There was no spark until it cooled down, so I put the voltage meter to it. But, there was also no water and some oil coming out the pee hole, so I took the screen off the water inlet and found little pieces of the water pump in there. Then, I ran a compression test - 35psi in each cylinder - no variation between cycinders, but awful compression. Since I'm already looking at $300-$400 minimum in parts without having torn down the engine, I don't know if its even worth the trouble. If it was, and it were a motorcycle, I'd just take the engine into a machine shop. What's my next move?

[99yam40]

low compression is probably due to the gauge you are using, I do not believe a motor with 35psi would even start.
taking apart to see what all is wrong just costs your time.
But testing ignition system would point to where the spark problem is happening

[99yam40]

impeller came apart so it got hot,
pull the head to see if head gasket is blown or something else is getting 2 stroke oil and gas into the cooling passages

[paulutions]

low compression is probably due to the gauge you are using, I do not believe a motor with 35psi would even start.
taking apart to see what all is wrong just costs your time.
But testing ignition system would point to where the spark problem is happening

The compression gauge is brand new, although it is Harbor Freight. It works on my car. Tried it again this morning. 35psi hot and cold, started right up, but blows some smoke. Nothing but air coming out the peep hole. So, I know it needs a new impeller, thermostat, CDI, and ignition coil. Looks like it might need a head gasket or a valve job or something else that's giving such low compression. I am about to do a leak down test, but would put money on it being unacceptable as well. On a 4 stroke car or motorcycle (this motor is 2 stroke) if I found a leak that was likely a head gasket, I would pull the head and take it into the machine shop and just drop it off to have any valves, seals, etc done, then just pick it up, check the clearances (which are usually good) put in a new head gasket, bolt it all back together and go. If I have to get into the bottom end of the motor too, I usually either take the whole thing in for a rebuild or start looking for another engine. If I am already looking at $400 in parts and hours of my time on this old 2 stroke boat motor. If have to have anything machined, I do not know if I see any advantage in continuing with this motor. I want to be sailing, not twisting wrenches. Thanks

[99yam40]

there are no valves or seals on a 2 stroke outboard motor head.
just metal that spark plugs screw into and seal off the top of cylinders.

test the inputs and outputs of the CDI, no reason to replace parts that are not needed it they are not bad.


by pulling the head you will find out what is wrong with the cylinder/pistons//rings and if you break bolts doing that then it will give you an idea on how far you will have to tear it down to fix.
no cost except time to take apart

where do you think air coming out of the tell tail would come from.
there is no air pump except the pistons, and the combustion chambers are suppose to be sealed from the water cooling system where the tell tail is

so far it could be a head gasket and water pump, then find out what is going on with spark going away.

you do not have to buy any parts until you know what is needed

[TownsendsFJR1300]

Plus 1 ^^.

Just put some time only into it and pull the head. Agreed, it's probably the head gasket. A leak down test W/O pulling the head may show that.

Both cylinders exactly the same, super low, indicate that head gasket, especially since it was overheated..


On a related note, I just put together a 16 HP Briggs (Zero turn mower-freebee), single cylinder, with a locked up engine. Tore it down till I found the issue and ended up rebuilding a good part of the engine (new head, piston/rings). An exhaust valve seat came loose, spit out the exhaust valve (OHV) which busted and trashed the head and piston while running. Cylinder/block looked brand new... It was worth fixing and just finished it a couple days ago..



.

[paulutions]

Thank you. I am going to go ahead and order the head gasket, impeller, CDI and coil, since these are things that I know are definitely wrong. Then, I'll cross my fingers and hope I won't run into anything else, lol. I appreciate your advice. I have somehow managed to have gotten this far in life without having worked on a 2 stroke before, so I really appreciate it. I imagine I'll want to measure the cylinder walls for warp? I remember that the machine shop would blow chalk or something in the cylinders to find cracks. I haven't seen anyone suggest that. How should I check them? Is there a particular resource or video that you like? Where can I get a shop manual for this thing?

[TownsendsFJR1300]

For my Briggs, once I had the head off, there were still original hone marks on the cylinder with absolutely NO scoring.

I could only measure the 2nd piston piston ring (top ring was crushed in the top groove from the impacts), which was .018", just outside spec(and 15 years old.)
So I knew the block was pretty much fine (max RPM's are about 3,600 RPMs- so it's really nit a screamer). *The new top ring end gap was .004". the second NEW ring, .014"(vs .018" of the old one, so some ring wear)

Obviously you don't have valves, but once apart, you'll see the condition. You can either use the appropriate measuring tools to measure the cylinder bore or if "looking" good, measure with a ring in the bore in multiple places. If that measure varies ALOT, you know you may have some "bore issues"

The main difference (you likely know), is the piston has a notch to keep the piston rings from rotating on the piston. If they did, they'd catch a port and destroy the engine..


I personally, would hold off ordering anything till I knew the block was good.


I've never heard/seen a cracked block here in 10 years or so... Corrosion is most prevalent, head gaskets, etc. I'd be really surprised you had a cracked block as other issues will arise FIRST..



A pic of my above mentioned engine with the new piston, being assembled:


DSCN0549.jpg

[99yam40]

you are not taking our advice.
take it apart to see if it comes apart without breaking bolts and see what all is wrong before ordering any parts.
you may not want to fix it after you find what you find

a 27 year old motor may not come apart easily if it has been around salt water

[TownsendsFJR1300]

I posted these just before you 99 waiting for it to "be approved".

For my Briggs, once I had the head off, there were still original hone marks on the cylinder with absolutely NO scoring.

I could only measure the 2nd piston piston ring (top ring was crushed in the top groove from the impacts), which was .018", just outside spec(and 15 years old.). So I knew the block was pretty much fine (max RPM's are about 3,600 RPMs- so it's really nit a screamer). *The new top ring end gap was .004". the second NEW ring, .014"(vs .018" of the old one, so some ring wear)

Obviously you don't have valves, but once apart, you'll see the condition. If it's worth fixing..You can either use the appropriate measuring tools to measure the cylinder bore or if "looking" good, measure with a ring in the bore in multiple places. If that measure varies ALOT, you know you may have some "bore issues"

The main difference (you likely know), is the piston has a notch to keep the piston rings from rotating on the piston. If they did, they'd catch a port and destroy the engine.


Pic of my Briggs with new piston installed / being assembled:

.. DSCN0549.jpg