1977 200 hp Johnson

[Johnson Outboard]

I have a 77 200 Johnson that I have owned for 30 years. A few years ago it started this thing were you start it cold, Idles and runs good up to normal 5500 rpm, all good. You shut it off for maybe 15 to 30 minutes, start it, idles fine, go to take off and it dies like lack of fuel. You can gradually give it throttle and choke it until it will gain rpm. Once re-established it runs great until you shut it off then its the same thing all over again. Seems to be worse the warmer the ambient air temp. I have rebuilt the carbs, replaced all fuel lines, fuel pumps, fuel selector switch, base gasket, check the reeds (boyesen reeds in good shape),Tanks are vented good and fuel pick-ups tubes are good. It runs at a steady 145 degrees. The motor has about 800hrs on it. I have installed the later model thicker head gaskets and it has 100 to 105 lbs of compression in all cylinders. The thicker head gaskets drop the compression from the stock 115 to 120lbs. The local boat mechanic thinks it could be the sealing rings on the crankshaft between the cylinders are worn to the point that once its warmed up and shut off its allowing the fuel charge to leak past. I just can't help to think its something else do to the top carb doesn't have a choke plate. I would hate to spend the $ replacing the sealing rings only to have it have the same prob. Any Ideas out there? Thanks for responding

 

[Johnson Outboard]

Has anyone had any experience with a motor with worn crankshaft sealing rings? What does it run like? What are the symptoms? Thanks

 

[emdsapmgr]

The fact that only 2 of the 3 carbs have choke butterflys is certainly an inconvenience when starting the engine cold. My 79 200 was a pain. Likely this inconvenience is not related to you your running issue. I'd think that once the engine is shut off, that fuel may be siphoning back into the tank from the carbs. On re-start, it may run on the small amount of fuel in the bowls, till it consumes that, and has to wait for the pumps to suck/pump the fuel back up from the tank. Couple of things to check. 1. make sure your hose connections under the cowling are all tight. Any air leak in the fuel system is a fatal fault. That dual pump engine has a lot of fuel connections. 2. If you've recently replaced the fuel hoses under the cowling, are they factory hoses, or just bulk hose from an auto parts store? Some of the hoses bend in sharp corners. Bulk hose will kink at the bend and will restrict fuel. 3. Possible the anti-siphon valve in the built-in fuel tank is stuck open. That would certainly enable fuel to drain back into the tank once the engine is shut off. 4. Check the fuel pickup inside the tank. Many of the plastic pickup tubes get loose under the tank head (with age) and the fuel system can suck air where the hose is pushed onto the tank head-instead of fuel from the bottom of the pickup. Unlikely seal rings are the problem. They are not really a wear item. A personal side note: I'd be inclined to put the original 456/457 heads back with the stock (thin) head gaskets. Unless you rejetted the carbs, your carbs are still supplying all that fuel and you are not making close to 200 hp. That is not so much a problem is it is probably overfueling at mid-range to WOT rpm's. So, performance is degraded due to low compression, and it's overfueling-which further reduces max throttle capability. When you go back to the thin head gaskets, go with premium fuel only.

 

[Johnson Outboard]

When I replaced all fuel lines All under hood were factory hoses. Fuel pick ups are bronze in the duel saddle tanks. It never had any kind of check valve except in the primer bulb. I replaced the tank selector valve and the fuel lines that run from each tank to the valve to a water separator filter then primer bulb (which was replaced)then to engine. The primer bulb is firm when it does its thing and dies so it doesn't seem like its having an issue picking up fuel. I'm considering trying an electric fuel pump between the filter and primer bulb. When I checked with dealer the only head gaskets available were the thicker ones. I would like to go back to originals if I could find a pair. I have always run premium for the last 30 years (non-oxy since oxy fuel started) so that's not an issue. Definitely notice a power drop with the thicker head gaskets. It has always run good with this same fuel line configuration and will still hit 5900 rpm with just me in the boat all trimmed out even with the thicker gaskets just not as good out of the hole

 

[Johnson Outboard]

It does seem like what you are suggesting is a scenario. I am baffle as to what has changed. Its weird and since I have gone through all fuel stuff the local mechanic is stuck on the crankshaft wear rings between the cylinders. But if the fuel charge was leaking past the rings the top cylinders would be out of fuel so to speak and its the top carb that doesn't have a chock plate. I'm just not convinced enough to tear it down that far.

 

[Johnson Outboard]

It does seem like what you are suggesting is a scenario. I am baffle as to what has changed. Its weird and since I have gone through all fuel stuff the local mechanic is stuck on the crankshaft wear rings between the cylinders. But if the fuel charge was leaking past the rings the top cylinders would be out of fuel so to speak and its the top carb that doesn't have a chock plate. I'm just not convinced enough to tear it down that far.

 

[emdsapmgr]

So, a couple additional comments: The factory never made a water separator for that engine. It was not made for one at the time. While I'm a fan of them, it's possible that the dual fuel pumps won't draw properly through it. So, perhaps a test without it in line might at least prove or disprove keeping it installed. I run the large Mercruiser water separator kit on my V6 and it has not affected running. The fuel hose bulb will get hard the first time you pump it up when cold-starting the engine each morning. When the pump starts and sucks fuel through the line, the bulb will soften somewhat-but should not collapse on itself. If the bulb stays hard when running, that is a problem. Sounds like yours is functioning normally. The original thin factory head gaskets 320745 have been superceded to 766779. See your local Bombardier dealer. Hopefully, you replaced the two fuel pumps with factory ones, both of the old part numbers supercede to the same single part number: 438559. These pumps cannot be rebuilt, purchase them new. Those are the only pumps to be using on that engine. I use the Bombardier plastic hose "snap clamps" on all my fuel connections.

 

[Johnson Outboard]

I've had the water separator canister filter for the whole time I've owned the boat and I change it the beginning of every season, It has never had any water in it either. So I just can't think it would be an issue. Yes I did use the factory fuel pumps. Thanks for the part # for the head gaskets I will look into it. I was even thinking maybe with the lower compression the pumps weren't seeing enough crankcase pressure to operate properly, but then why would it run good right out of the gate and only develop the prob after its been run then shut off. The fuel draining back out is more plausible but its drawing from a canister full off fuel. so it would have to force the fuel through the filter back to the tank. I have cable ties on the fuel connections which have always worked. If it were pulling air it seems like you would see a leak when you pump up the primer bulb.