Craig, I agree with Tod that fuel delivery is the likely culprit--especially if you tell me that it has been six months or more in storage without draining the carb. I also agree that this is not a Tohatsu or Nissan (or Mercury--they are all the same save for paint) issue. I had this happen to my Honda when I forgot to drain the carb prior to putting into storage. I seldom see ignition problems with newer outboards (or other power equipment), as they virtually all have solid state ignitions that preclude wandering spark timing, etc. They usually either work or they don't--no middle ground! About the only things I have seen fail ignition-wise of late are burnt spark plug electrodes or chafed-through spark plug wires. The latter would be very obvious. A few points: 1) Varnish formation/buildup seems to be worse with the new gas formulations (oxygenated, MTBE, and other formulations). I am far from a chemist, but I can tell you that the new types of gas do not seem to have anything like the shelf life of 'old' formulations. I run up against this problem all the time with seasonal-use power equipment, and nine times out of ten, I end up removing the carb and either chemically (Tod is correct--be careful) or physically (wire/compresseed air) cleaning the bowl, jets, needle and seat, etc. I now use a fuel stabilizer for shorter term storage, and empty the bowl for anything beyond a few months. 2) Another problem with *some* formulations is that the additives attack *some* rubber seals, gaskets, and needle valves. If you get the carb open and there is no apparent varnishing, but notice weird, distorted rubber parts, this could be the culprit (I doubt it, though, as most manufacturers switched to improved 'new gas' rubber compounds in recent years). 3) I would be curious to know how the shop in question (which, by the way, does not sound very impressive diagnostics-wise) tested for spark. If they were lazy (and it sounds like they were), they likely just pulled the spark plug wire boot, and tested for arc while pulling the recoil starter. This tells you whether your coil is delivering spark to the plug, but it does not tell you whether the plug is actually sparking within the combustion chamber. The proper test is to remove the plug, ground the threaded portion to the engine block, and pull the recoil starter (with the spark plug wire attached, of course!). That said, it would be very unusual for a plug to just give up while in storage, but it is a very easy test to run. 4) There is one other (very easy) way to verify that ignition is not the culprit. You can spray a VERY SMALL amount of starting fluid directly into the air horn of the carb. I say VERY SMALL because you do not want the engine to over-rev (and it will!) by spraying too much. In all likelihood, the engine will start on the first or second pull, rev up a bit, and then die very soon thereafter. Again--a little of this stuff goes a very long way!!!! Before you do this (if you do this) pull the starter several times (fast) to get some oil s plashed around. 5) When you pull the recoil starter rope (with the same pull as you normally would to start), do you feel the same kind of resistance that you are accustomed to? While very highly unlikely, compression loss due to a burnt or bent valve, or cracked ring(s) could keep an engine from starting cold--especially a one cylinder. So, I am betting on varnished fuel causing a stuck needle valve, plugged jet(s), or in an extreme case, clogged fuel line, bowl, and the needle valve and jets. There is one more thing to check. Most of these motors have either a very fine mesh fuel filter at the carb, or an inline paper media or mesh filter. Make sure that this is clear, and try blowing through the fuel line as well (this may or may not be possible without defeating the check valve where your external tank hose hooks up. If your 4hp Toha-Nissan has the internal tank, also look in the very bottom of the tank where the fuel line exits. There might be a very fine mesh screen there as well. Some of these screens are designed to allow the flow of fuel, but not water, so make sure there is none present. Oh--and this should go without say--make sure that you start with new, fresh fuel! I will be eager to hear what you find. If you don't want to tackle this yourself, a *good* shop should be able to do a COMPLETE diagnosis in less than 1/2 hour (an hour if removing the carb is particularly difficult). The repair--assuming varnish--should not take more than another hour total.
From what you said, I don't think I would include your first shop in the *good* category!
Best, Scott In a message dated 3/21/05 6:35:00 PM, montgomery_boats-request@mailman.xmission.com writes:
. . . Nissan (Tohatsu) 4-stroke? I know some list members own them, but I'm wondering if anyone out there, unlike me, knows anything about them.
I own a 4-horse 4-stroke Nissan (Tohatsu), but know nothing about it, except that, last Fall, it stopped starting.
I've had it at a local repair shop, where they can find nothing wrong, yet cannot start it. They told me they were giving up. The shop is most familiar with Johnson and Evinrude, but services all brands, including, a few times in the past, this exact motor. They thought perhaps a Nissan dealer could find a cause they were overlooking.
Any ideas? I bought the motor, on sale and tax-free, from an Indiana dealer and it's not particularly practical to take it back to him.
The motor ran beautifully and reliably for two seasons before it mysteriously quit last Fall . . .