Starts on land but not in water

[ctparks]

I have a 1980 260 Mercruiser that I had just changed the stern drive water pump, gear oil & T-stat and gasket...thats all I have done to it since this happened. I can have the ear muffs on and it will start and run fine with no problem of overheating, I can move into fwd, rev & neutral with no problems. When I put her in the lake, it would just turn over but never start, even after squirting some either into the carb. I put her back on the trailer & tried again out of the water & she fired right up as if nothing was wrong, so I lowered her back into the water with it running and it continued to run...I made a circle by the docks...went to reverse...back to fwd and then when i dropped it back to neutral it died and same as above...would not start again while in the water. I did this a couple of times before giving up for the day.

Also, on another question that may be related in some way...my throttle linkages, when I move the throttle fwd & back, the 2 linkages at the back of the motor move first and then the linkage going to the carb dont start moving until I'm about 1/2 throttle....I don't believe it was like this before, but I have not messed with the rigging of those linkages at all.

Any help you guys can provide on this would be greatly appreciated as always.

 

[JustJason]

Re: Starts on land but not in water

when's the last time you tuned up your boat?

 

[ctparks]

Re: Starts on land but not in water

when's the last time you tuned up your boat?

I bought the boat in February and was told it just went through a tune up. The distrubutor cap & plug wires look new, the carb appears to have been just rebuilt. I pulled all 8 spark plugs & they looked used but not in terrible shape. When I changed the water pump...the impellar was in one piece but hard as a rock. the t-stat looks like the orginal from 1980. That is about as far in it as I've got. when I have it running on land, it idles smooth and runs great...I've had it in the water one time before this when it started fine in the water and had no problems until it started to overheat and I then limped it back to the ramp and thats why I ended up changing the water pump & t-stat.

 

[180shabah]

Re: Starts on land but not in water

I would look into the shift interrupt/lower shift cable.

 

[JustJason]

Re: Starts on land but not in water

1 check your base ignition timing.
2. check your boats fuel system as explained here... http://forums.iboats.com/showthread.php?t=283269 While your in the fuel system make sure you take a fuel sample and check it for water.
3. check your engine compression.
4. look for any evidence of air leaks at the edges of the manifold and the carb base and carb throttle shaft with some 6 in 1 foaming spray oil
5. rebuild your carb.

 

[Don S]

Re: Starts on land but not in water

I put her back on the trailer & tried again out of the water & she fired right up as if nothing was wrong, so I lowered her back into the water with it running

Well, there is one dead raw water pump. I also suppose you had the outdrive in the full up position while it was running????

After you replace the water pump and impeller from that trick, and check to make sure you didn't damage the exhust hoses, when you put it in the water and it won't start, try checking for spark.......... You did put kill switch lanyard on when you had it in the water didn't you?

 

[meesh]

Re: Starts on land but not in water

You beat me to it Don. Fried raw water pump was the first thing I thought of when I started reading this post. I agree with Bubba, if it runs fine on land it does'nt need a tune up. Somethings shorting out your ignition when your on the water. Loose wire to your coil? or your coil wire flopping around? Your going to need to get your meter out and start going through the system until you find the short.

 

[ctparks]

Re: Starts on land but not in water

Well, there is one dead raw water pump. I also suppose you had the outdrive in the full up position while it was running????

After you replace the water pump and impeller from that trick, and check to make sure you didn't damage the exhust hoses, when you put it in the water and it won't start, try checking for spark.......... You did put kill switch lanyard on when you had it in the water didn't you?

Sorry, it's been so long since I've replied to this post. No time to mess with it lately. when I was starting it on land the outdrive was down and in the water, I just brought it out enough to get the exhaust out of the water. As long as the exhaust is out of the water, rather with ear muffs on or stern drive just in the water, it will start and run fine. It's when the exhaust gets down in the water that I start running into the problem. I'm thinking that it's got something to do with backpressure in the water. Before all this, it did overheat once...would it be possible if the exhaust flaps broke off in there, cause this problem??

The kill switch never comes off...so yes it was on there. Any help, as always is greatly appreciated.

 

[Maclin]

Re: Starts on land but not in water

Sounds to me like you have it figured out now. The water adds quite a bit of back pressure so if you already have a blockage then putting it in the water puts it past the point where the engine can overcome.

 

[ctparks]

Re: Starts on land but not in water

Sounds to me like you have it figured out now. The water adds quite a bit of back pressure so if you already have a blockage then putting it in the water puts it past the point where the engine can overcome.

Yea, at least I hope I do. Thats the only thing I can think of that could be the problem here. Putting the exhaust in the water is really the only thing I can't duplicate on land. I've got to get some time so I can look in the manual to see how hard it is to look/change those exhaust flappers.

 

[Maclin]

Re: Starts on land but not in water

You will need to remove the lower unit to get the flapper pieces out.

 

[Don S]

Re: Starts on land but not in water

The idle relief ports are ahead of anyplace the flappers could lodge and cause problems.

Let's go back to basics here. When it won't start, have you checked for spark?

 

[a70eliminator]

Re: Starts on land but not in water

My engine always starts easier on muffs, when the exhaust outlet is underwater there is a backpressure effect, the difference I notice is rather than starting with just a bump of the starter it now needs a just a bit more cranking and 1/4 throttle to start when underwater, the idle also is reduced just a tad with exhaust submerged, like the 600rpm idle I have on land is reduced to about 550 in the water.
you may have to just hone your starting technique a little to find what your engine likes, try 2 shots of accelerator pump followed by 1/4 throttle, I don't know about fuel injection though.

 

[ctparks]

Re: Starts on land but not in water

The idle relief ports are ahead of anyplace the flappers could lodge and cause problems.

Let's go back to basics here. When it won't start, have you checked for spark?

Thanks to everyone for replies. I have not checked for spark when it won't start in the water, but with it being able to start everytime and run great when out of the water...could ignition be the problem only when in the water?

I'm not even sure that the flappers are broken off and lodged somewhere...haven't got in and took a look at that..just my theory since it has overheated once and prior to it overheating and me changing the raw water pump & impellar & t-stat it would start and run fine in and out of the water...so i thought it made since in my headthat something to do with backpressure has caused it to not start when the exhaust is submerged. Again, Thanks to everyone for all your help and guidance with this.

 

[CharlieB]

Re: Starts on land but not in water

The backpressure difference in and out of the water changes the amount of idle fuel required.

A slightly richer mixture is needed in the water.

The choke and accelerator pump should be enough, remove the spark suppressor and look at the choke, open the throttle ooonce to 'set' the choke, did it close fully?

Early on you stated that the carb was recently rebuilt.

The choke may be set too 'lean' making it bit harder to start on the water.

 

[ziggy]

Re: Starts on land but not in water

put her back on the trailer & tried again out of the water & she fired right up as if nothing was wrong, so I lowered her back into the water with it running and it continued to run...I made a circle by the docks...went to reverse...back to fwd and then when i dropped it back to neutral it died and same as above...would not start again while in the water. I did this a couple of times before giving up for the day.

hope ya had the hose on it when ya started it out of water or the new waterpump impeller is toast.

I would look into the shift interrupt/lower shift cable.

that seems like a good place to start. maybe the shift cable, or something like the cam that actuates the interupt sw. is sticking from lack of lub, or a bad cable. i'm thinking elec. too. i'd be looking to see if i had spark under the no start condition...

 

[Don S]

Re: Starts on land but not in water

Ziggy, have a look at post #9.

 

[ziggy]

Re: Starts on land but not in water

when I was starting it on land the outdrive was down and in the water, I just brought it out enough to get the exhaust out of the water. As long as the exhaust is out of the water, rather with ear muffs on or stern drive just in the water, it will start and run fine. It's when the exhaust gets down in the water that I start running into the problem.

ok Dons, i'm still learning to read ya know.

so the way i get this is, it starts fine, exhaust out of the water, then ya put it in the drink w/o shifting at it won't start. put the exhaust above water and it'll start again. exhaust back under water and it won't. if that's the case and the only change between start and no start. then the shift cable would be eliminated.

. Putting the exhaust in the water is really the only thing I can't duplicate on land.

guess i was thinking, that he can't duplicate actuating the interrupt sw. either. but if no shifting is done, then i guess that aint the problem. and ya start leaning the way everyone else is. exhaust restriction.... still seems like it might be a good idea to see if there's spark under no start condition. at least eliminate it from the list of possibilities.. if ok, then go look for flappers broke off from the overheat.. i'll be interested in seeing the outcome of this..

oh, and i'll try to read closer too... not reading has got me in trouble before i believe...

 

[ctparks]

Re: Starts on land but not in water

The backpressure difference in and out of the water changes the amount of idle fuel required.

A slightly richer mixture is needed in the water.

The choke and accelerator pump should be enough, remove the spark suppressor and look at the choke, open the throttle ooonce to 'set' the choke, did it close fully?

Early on you stated that the carb was recently rebuilt.

The choke may be set too 'lean' making it bit harder to start on the water.

Yes it was rebuilt, but before it overheated the first time out this year and I changed the raw water pump it ran and started fine in and out of the water.

guess i was thinking, that he can't duplicate actuating the interrupt sw. either. but if no shifting is done, then i guess that aint the problem. and ya start leaning the way everyone else is. exhaust restriction.... still seems like it might be a good idea to see if there's spark under no start condition. at least eliminate it from the list of possibilities.. if ok, then go look for flappers broke off from the overheat.

I have also read the sticky on the interrupt sw thinking it may have something to do with this. I can see the sw engage & disengage when I move the throttle fwd and rev. I even removed the sw while trying to start in the water so that it was open the whole time to see if it would start then, with no luck.

What would cause there to be no spark/ignition in the water when I have it on land? It's a bit of a hike to the lake so dragging it down there to see it fail is a pain. I'm going to go ahead & change out all the plugs & the coil being they look a little worn and tear into the exhaust to see what I can find out about the flappers. If the flappers did break off, I hope I can get to them without having to remove the outdrive.

 

[Don S]

Re: Starts on land but not in water

What would cause there to be no spark/ignition in the water when I have it on land?

Are you sure there is no spark, or are you just guessing? Throwing a bunch of money at it in parts when you don't even know what the problem is, is just plain crazy and expensive.
Take it to the water, take some tools and test equiment and find out what is missing.
You need ignition(spark at the right time), compression, and fuel. If you put it in the water and it doesn't start, check for spark. If you don't have spark, troubleshoot the sysstem while it's in the water and find out what it stopping it. If you have spark, and you know the compression is good, then you have a fuel problem.
It may be such a thing as you have the bow of the boat real low to run it on land, when you have it in the water, the stern is lower and the carb is at a different level...... Now imagine if you will water in the carb and fuel tank.
Just don't start throwing parts at it.