Capitanmike

I have a 1989 Johnson vro v4 90hp, and im having some issues. I recently put in a new impeller due to overheating. the boat was running fine prior to this now every time I drop the engine into the water the engine boggles and dies. I spoke to a mechanic and he told me it sounds like one of the exhaust rubber silicone seals broke (thats the rubber piece that goes around the exhust part that looks like a little boot next to the water pump in lower unit) when he mentioned that I recalled that rubber seal breaking and I put it back together broken. could this be causing the engine to die (Someone told me that part is not even needed) when it's put in the water? it runs perfectly fine on muffs but not in the lake however when I'm in the lake and this happens I lift the engine just enough for the muffs water intake to be in the water it cranks right up but as soon as I drop it in the water it dies again please keep in mind this started happening after the impeller install. Any and all help will be highly appreciated thank you.

Capitanmike

here is a pic of the rubber part I'm talking about.

BUP

iTrader: (9)

do you have the exhaust outlets above the waterline when you are in the water starting and idling around ? OMC ignition set ups are junk, Bad power paks and timer bases are big problems for many J/E engines. Spark test and comp test engine as well.

Side notes. Many colling over heats can be needing the housing and wear plate and gaskets replaced with all new. Also it important to use OEM J/E impellers not Sierra nor ebay impellers. Is your VRO properly working - it does both sides the fuel pump side and the oiling side of the coin. They are junk as well, back in the day we would take them out and properly convert fuel / oil mix and install the OMC mechanical fuel pump. Back then the square mechanical fuel pumps were like 50 bucks. Just saying.

mrv8outboard

So my first question is how bad did the engine overheat? How long was it run during your overheat? The water pump is the only thing you changed? This is a bubble back cross flow powerhead. Do you have a non contact temperature gun? You can check each head for proper temperature. A cold running engine does not perform well. If you did not disturb anything else during you water pump service these are some thing to consider.

The degree of overheat can damage the following components, Relief Valves and Grommets. Thermostats. The most over looked Water Deflectors. Another thing that happens in two strokes when overheat is piston scuffing. This is usually accompanied stalling at idle or having to have the idle set high to keep running and stalling when put into gear. This condition can not be diagnosed with a compression test. Visual test is required. (sometimes running it on premix at 25:1 can seal up the skirts and it will run but the pistons are toast at that point)

Now back to what to do. Perform a compression test and a spark test. Check the spark plugs for signs of damage to engine. Look in each cylinder for scuffing of the cylinder walls. Now if these all pass, good. Your engine has an Enrichment Solenoid and we can use this as a tool. Star and run the engine on the trailer with the water intakes in the water and the engine will run, as you submerge the boat further into the water to were it will stall just start pushing in and releasing on the key to pulse the Enrichment Solenoid. If it responds try to keep it running enough to confirm that by enriching the fuel it will run.

If the engine runs it is time for fuel system maintenance. Carburetor rebuilds and fuel filters. Once the engine runs you can perform a vacuum test on the fuel system. Leave the VRO alone as these are misunderstood and removed or replaced needlessly. (I still run VRO's on my raceboat's V8's outboards).

So the quick and simple answer for not being there in person with the limited information is that it is running lean or running on two cylinders or you have scuffed pistons.

BUP

iTrader: (9)

I agree about the deflectors as they can cause issues of cooling. I would pull the head off and check that out and conditions. Not hard to pull the head of this style 2 stroke outboard.

By no means I am outboard expert but about average when I had had to work on them.

BUP

iTrader: (9)

It might help to check out the J/E forums, I do know that a few J/E techs help out on the site, I personally know an old time J/E tech at one time was very looked up to for the brand that helps out once in a while on their forums . This site is all mainly performance I/O's