1993 V4 Johnson

[cleve]

Possibly going to look at used Javelin with a '93 Johnson 90hp.
What should I look for on this engine? Common issues? He says the oil injection VRO has been deleted, which is a plus IMO. Also had a recent carb service and new fuel pump.
Haven't discussed whether trying it on the water is an option. Would a cold compression test tell me anything? Specs?
It's about a 2 hour drive, so I will want to make a decision before I leave there.

 

[jbuote]

Still new to boating, but definitely a compression test. Should be within 10%(I believe) of each other. Also spark test. Spark should be able to jump 7/16th open air gap with a crisp snap.

I'm sure others here could be more detailed, but the short answer to your question is.... YES... Do the tests... lol

 

[jbuote]

Scrolling down through this sticky topic you'll find info on checking engines...

​Hope it helps, even if only a little...

 

[cleve]

Ended up buying the boat. Compression was 95-105 psi on all cylinders.
Will be getting a service manual at some point. Are the ones for purchase on Iboats fairly detailed?

 

[racerone]

Remove the bypass cover on the lowest reading cylinder.-----Have a look at piston and rings.----Cost you a $ 2.00 gasket.

 

[boobie]

How's the motor run ??

 

[boobie]

Got a model # ??

 

[ezmobee]

Here's your manual http://www.ebay.com/itm/1993-Johnso...ash=item51cf7084f5:g:TdMAAOSw7NNT6BBI&vxp=mtr the OEM ones like this are fantastic.

 

[cleve]

Model #J90TLATS
Motor ran good. The throttle cable is a little stiff and it idled a little high.
I won't get a chance to dig into it until the weekend.
ezmobee, I ordered that same manual, but from a different seller on Ebay.

 

[cleve]

Have taken the boat out 3-4 times since I bought it. It has run great with no issues so far.
When I checked the compression the day I bought it, I just removed the kill switch and spun the engine over for each cylinder. Engine was cold.
I have since been told I was supposed to open the throttle when doing this. Would the compression read higher doing this?
The boat is no speed demon, but hard for me to believe it runs this good with @100 psi compression. No knock or rattle from the engine either. Just curious. Had one guy tell me it's time for a rebuild with numbers that low.

 

[ondarvr]

Opening the throttle won't really change anything on this motor, and compression gauges tend to not be that accurate and can read very differently from each other, so the actual number may not be important unless you know how your gauge reads. These motors tend to break rings and self destruct.

 

[racerone]

Opening the throttle on that 2 stroke engine does not change compression.---------Not sure where those tall tales come from ?