Starts great on land but hard to start in water

[Augoose]

1989 Mercruiser 4.3

I've read several threads about this being caused by back pressure in the water and a failure of the exhaust flapper, however the threads seem to end without the author ever getting back to tell what they found out. Does anyone have any experience with this?

I initially thought I needed to adjust the carb, as while I'm sitting in the water the boat will crank for several seconds until the engine finally starts catching with a low idle. After a few seconds and the idle comes up, and the boat runs like a top and sounds great at all rpm ranges. I also tried combinations of giving it a little throttle during starting and pumping the throttle once or twice then returning to neutral to start, but the improvements it makes are minimal.

Today while troubleshooting another starting issue, I had it on the trailer and just hit the ignition briefly to see if the starter would turn. Not only did it turn, but the engine started immediately. I quickly shut down, and so the engine was cold and stayed cold. I know I shouldn't have started it w/out muffs, but I honestly didn't think it would start that quickly considering that it takes up to 5 or 6 seconds of cranking in the water.

The other issue is that I recently had it in the shop to replace the lower shift cable and I had a transom seal kit put on. My question - would the technician, in replacing the shift cable and transom seal kit (including the exhaust bellows), have come across the exhaust flapper? I would be kind of miffed if he did that much work and left a faulty flapper - because I do hear a soft and inconsistent "clicking" or "ticking" sound at idle speed. I'm pretty sure its not a lifter as it is not consistent and it goes away as I speed up.

Sorry for being long winded...
thanks

 

[Bt Doctur]

Re: Starts great on land but hard to start in water

Flapper locations are in here
http://www.boatfix.com/merc/Servmanl/16/16D7R2.PDF

 

[Augoose]

Re: Starts great on land but hard to start in water

Flapper locations are in here
http://www.boatfix.com/merc/Servmanl/16/16D7R2.PDF

Thanks for the response. According to the diagram, it seems that the flapper is something that the tech would not have come across during a seal kit exchange, correct?

 

[6meter]

Re: Starts great on land but hard to start in water

Sounds like you need to give it some throttle while starting. Your "catching up to low idle" says that. Just make sure that you're not engaging foward while doing it.

 

[Augoose]

Re: Starts great on land but hard to start in water

Sounds like you need to give it some throttle while starting. Your "catching up to low idle" says that. Just make sure that you're not engaging foward while doing it.

I tried full throttle, 1/2 throttle, 1/4 throttle and then pumping it twice and then returning to neutral, but it didn't seem to help. Worth trying again though. Thanks for the suggestion.

 

[Don S]

Re: Starts great on land but hard to start in water

Those flappers, I don't care what they try to cover up, will not keep your engine from starting in the water. They could keep you from full rpm, but not starting.
Is your timing set to specs? Not by ear, but to specs?
Is your problem that it will not start at all or won't stay running.
WHen in the water, do you have spark?

 

[Augoose]

Re: Starts great on land but hard to start in water

Those flappers, I don't care what they try to cover up, will not keep your engine from starting in the water. They could keep you from full rpm, but not starting.
Is your timing set to specs? Not by ear, but to specs?
Is your problem that it will not start at all or won't stay running.
WHen in the water, do you have spark?

I wasn't necessarily thinking the flappers were keeping the engine from starting, but possibly water was getting past the flappers and causing some sort of back pressure? At least that's what I read on the other posts.

The boat itself idles and runs like an absolute top (once it is started). Sounds great, runs great, etc. It just has a hard time starting in the water - cranks for approx 5-6 seconds before it catches vs on land it will start in less than a second.

I have not inspected the timing as I felt since it runs so well the timing must be at least close - great gas mileage, good operating temps, one of those if it isn't broke, don't fix it situations I felt.

I was beginning to think the carb was just running lean and that was causing the hard starts, however when it fired right up while on land, it made me reconsider.

As for the spark - I have not tested it in the water to see if I lose spark for the 1st few seconds, but on land its obviously got spark because it starts immediately. Also, once it is running and in the water, it runs and idles perfectly.

Regarding the electrical system, what component can be influenced by whether the boat is in the water or not? I have run it all day in the water and upon trailering, not a drop of water came out of the bilge, so I'm confident I'm not suffering a leak.

Thanks for the help Don!

 

[Don S]

Re: Starts great on land but hard to start in water

I have not inspected the timing as I felt since it runs so well the timing must be at least close

I personally, would NEVER assume such a thing, or it will come back to bite you.