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I have a 2-stroke nissan 50hp ob. On occasions I forget to open gas tank vent prior to starting it becomes hopeless to start same day, (ruins the week end). My non-mechanic brain thinks its some kind of vapor lock in the carb. Anyone know of a procedure to fix situation like this (and save the week end)?

Also: the starter shuts off when the motor does not fire in 2 or 3 cranks. I ussually get it started after a few attempts. Has been this way since I purchased the boat. Now I'm wondering if this has been a startee fault all this time. Is the starter supposed to crank as long as the battery has juice, like cars? Or is it normal for the starter to quit (almost feels like something gets caught/stuck) if the motor doesn't fire? If not, I guess its another repair job.
Thanks for any leads,
RHC

!	kmclemore:
	RHC, I deleted your duplicate posting.

Add more detail if you can - year of motor, injected, carb, etc. How long are you grinding on it before the starter gives up? Is it firing at all when you're grinding or just spinning the crankshaft?

Do you smell gas when it's not starting, or do you see fuel in the water around the motor?

Do you leave the fuel line connected to the tank all of the time?

Look at the tank next time it happens and note whether it looks collapsed or bloated.

If you don't forget the vent, does the engine start ok all day?

Do you think you can reproduce the symptom for a mechanic?

Unless you are just flooding the stew out of it due to heat pressurization of the tank, you'll probably need some mechanic help with test equipment to figure out what is ailing you, since you indicated mechanical stuff is not your thing. It will help if you can reproduce it for the gear head.

Hi jimmyt,
Thanks for response. Yep, easy to reproduce. Starter cuts out in less than 1 sec if motor doesn't catch. If I dont forget the vent, motor starts no problem, after a few attempts. Starter still cuts off less than 1 sec in couple of attempts, but eventually motor catches. No deformation in gas tank, seems pretty rigid. For long storage, I remove hose. I typically start motor from home day befor outing, tnen leave it in. I keep vents closed when driving boat on trailer. When sitting in driveway during storage, I sometimes keep vents open on hot days to releave pressure in tank. If not, gas leaks through cap.

Did some you tube research. I think my solenoid bad.

I have a 1999 Nissan 50 hp 2 stroke and find it exceptionally reliable, it cranks for about 5 seconds when not started for months and then fires and starts every time, once started and run it cranks for less than half a second and fires every time, I wouldn't be in any hurry to replace this engine, it is very reliable, reasonably efficient and certainly powerful, i have no problem getting my boat to 16 knotts sometimes more depending on weight. Have it fixed, it doesn't seem right but get it right and you have a great motor.

Cheers Dennis.

Could be electrical, solenoid, starter even, but when you said "it seems like something gets caught" sounded like hydraulic lock - liquid fuel in the cylinder jamming the piston (flooded to the extreme). This is a bad condition that can cause damage if you keep trying to grind on it.

Almost sounds like 2 issues. One relating to hard starting and the other to do with starter motor not running long enough to work through the hard start.

With your new info, only about one second of grinding and starter gives up - sounds more electrical. If you have a bud with a volt/ohm meter, you might be able to locate the electrical issue without taking it to a mechanic - since you can reliably reproduce it. I would begin at the starter and see if the voltage goes away when the starter stops. No- starter could be problem. If voltage goes away at starter, move back to the solenoid and check to see if it is supplying power when the starter stops. If not, check to see if the coil voltage is remaining (small wires on solenoid) when grinding stops. If your coil voltage stays hot, but your big terminal to the starter falls off, you may have a bad solenoid. If your coil voltage falls off, could be wiring, ignition switch, etc.

Have you cleaned all of your battery terminals and "big wire" connections? If not, do that first. Could be a dirty or bad terminal connection. Fix the easy stuff first.

For the other issue, pull the hose after your home test start. Vent the tank before you launch and THEN reconnect the hose. Might give useful info if anything changes. You shouldn't have to do this normally, but you may have something else going on that makes it significant.

Mine stays in A/C garage, and when I got to the ramp a week ago, my plastic tank looked pregnant. Amazing how much pressure built up due to heating.

Good luck!

Thanks for the feedback, guys. I have to admit, replacement w/ newer motor crossed my mind. Professional servicing probably in order. Battery is brand new west marine. Battery connection is flat connector on threaded stud with wing nut, clean.
Also, about time I learned to start with rope crank.
Good winds to you,
RHC

UPDATE:
I spoke with someone at the Belmont Boat center. His input was: when you run with tank vent closed, gas runs out, but oil keeps pumping and carb gets full of oil. then restarting becomes really tough. This explanation sounded like a perfect explanation, so I set out to drain the oil from the carbs. I discovered the top carb bowl was dry, I sprayed some carb cleaner. The middle carb was draining what looked like clear gas, so I reclosed. I could not even get to the drain plug of the bottom carb. But I got the motor started !! Took the motor for professional servicing anyway. Shop tech confirmed 1 needle valve stuck shut, another was stuck off & on, only 1 carb was working properly. After service, motor starts instantly.

I still have the problem of engine quits at low rpm when in gear. VERY annoying when maneuverying trying to dock with strong current and crowded slips.
Not sure is this is dile adjustment issue, or if I need to learn how to switch between F to N to R without keeping in gear at very low rpm.

I had that problem with my 50 hp Nissan TLDI 2 stroke, when running at idle speed. Very annoying when trying to get in and out of docks. The engine was fouling plugs. I changed prop pitch and that seemed to help.

Hi Chinook,
My prop looks like its due for replacement. What pitch did you go with?
My plugs were all brand new.
Thanks