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So I've got a 26S (1991) with a 9.9 Evinrude looks like 1996 4-stroke. With the earmuffs on in my driveway, it starts up on first crank. Twice I've hauled it a couple hours up the road to Wiskeytown and get it at the ramp, and nothing. It cranks fine, but no start up. The first time I just sailed off the dock and the next morning, after spending the night at anchor, with a little work and choke cleaner, it started up. Yesterday, my wife wasn't keen on leaving without a motor (just the 10 yrs old boy and his friend were with me on the first occasion, they have far more faith in my abilities than they should ) so we hauled out and went home. That night it didn't start in the driveway, but this morning, first crank, it started up no problem.
Some basic research indicated it might be backpressure on the exhaust that keeps it from starting up in the lake. The causes may be, according to the research, compression, spark or bad fuel. I pulled the sparkplugs to do a pressure test but my tester is 14mm and too large, so I've ordered the correct size. The plugs looked okay. The fuel is fresh and I put additive into it to help.
Anyone else experience this issue? Am I on the right track or are there other known causes?
Thanks
Bill V
SV Areion
M26S 1991

Get new plugs and good fuel first off.

Water should not cause a significant amount of back pressure to prevent you from starting, but the water could be providing too much resistance on the prop to allow a start. Make sure it’s in neutral, if it has a transmission. Make sure the fuel is able to get into the carb, I assume you have a bulb pump and are pumping it till firm.

BillyBobV wrote: ↑Sun Jun 13, 2021 8:27 pm That night it didn't start in the driveway, but this morning, first crank, it started up no problem.

...The plugs looked okay. The fuel is fresh and I put additive into it to help.

Welcome to the forum, Bill. Sorry that your first post is about a finicky outboard.

Fresh fuel was a good move. Are you running non-ethanol fuel?

So, it didn't start in the driveway at least once. That would seem to eliminate the back pressure theory. I don't know everything, but an outboard that won't start in the water, due to being in the water, sounds a bit off.

Descibe your cranking procedure in detail. For example:

Orient bulb with discharge end up (credit-Tomfoolery)
Pump until firm.
Engage choke.
Pull rope briskly (engage starter if electric start) - you say it cranks fine but no start implying electric start.
Note if engine pops, backfires, or otherwise indicates there is ignition; or merely just turns over.

Also, note:
Is there a fuel slick around the motor in the water after failed cranking attempts?
When you pull the engine cover after it fails to start, do you get a strong fuel smell? Is there fuel in the carbs?
Does the engine have a choke? Have you verified it works, if electric? I have a mercury on a bass boat that has to be choked at the air box by hand with the cowl off - because the choke design is not functional.

First step: Agree with Massey. Get new plugs first so you eliminate that altogether. Many of my issues with small engines have been solved by new plug(s). May not be your issue, but worth doing to be sure.

Note history. Is this motor new to you? If not, has it always started in the lake before? If motor is new to you, have you ever seen it start reliably in water (test sail?)

Elaborate on your "with a little work and choke cleaner" comment. Were you using the choke cleaner for starter fluid - i.e. Did you spray it in the carb, then try starting? If so, this would indicate a fuel/choke issue in lieu of spark.

When it's in the driveway, is it stored vertically? Do you tilt it for the drive to the lake?

Sorry for all of the questions, but trying to diagnose engine troubles in writing isn't easy.

Do you run the carb dry before you store the engine, or transport it? If the engine gets transported laying down with a full carb, you could simply be flooding the engine. When you finish running the engine, unplug the fuel line before you shut the engine off and let it drink up the fuel in the carb. This will do 2 things for you… one, prevent flooding, and fuel spilling out of the carb into the housing. And second will prevent the fuel from leaving nasty deposits in the carb that will require a rebuild to clean out. If the pilot jet gets clogged, you pretty much will have to replace the jet because of how small they are.

Thanks Massey! That seems like a great tip about pulling the fuel line and letting the carbs run dry. That's how I tend to keep my other small gravity-fed carbureted engines (mowers, generators, etc.) crud-free and in good shape after each use...that and using ethanol-free with a dash of StāBil 360 Marine with maybe a slug of SeaFoam and/or Marvel Mystery Oil in the fuel.

The Honda BF50A has a fuel pump though, and from the motorcycling and automotive worlds I'm led to understand that some fuel pumps, being cooled by the fuel itself, may react poorly to being run dry. Of course, such pumps are often within the fuel tank itself. But what say you to that concern? I don't know enough about my BF50A (2001?) to have enough knowledge of the matter. I drain its bowls manually before wintering with the little screw and hose setup as per the manual, have swapped its prop, changed its oil, water impeller, drive and trim fluids, cleared "pee hole cloggery" a couple of times, but that's about it.

Thanks everyone for the responses, I appreciate them all.
Massey, I'm going to try your suggestions on running the fuel out; flooding could very well be the problem. I've left the fuel lines hooked up and the altitude change could be enough to cause it to flood while in transport. It wasn't an issue last year but who knows.
I've already ordered the new plugs and will be pressure testing it anyway, since I'll have the time to do that before I go out next.
Jimmyt, thanks for the welcome and yes, I understand it is difficult to diagnose based on written descriptions. I'm going to do the plugs and assuming there is no compression issue found when I test it, try Massey's suggestions. I'll post back here the results after I'm at the lake next (could be a month or more depending on the kids schedules).

Bilgemaster wrote: ↑Tue Jun 15, 2021 5:47 am Thanks Massey! That seems like a great tip about pulling the fuel line and letting the carbs run dry. That's how I tend to keep my other small gravity-fed carbureted engines (mowers, generators, etc.) crud-free and in good shape after each use...that and using ethanol-free with a dash of StāBil 360 Marine with maybe a slug of SeaFoam and/or Marvel Mystery Oil in the fuel.

The Honda BF50A has a fuel pump though, and from the motorcycling and automotive worlds I'm led to understand that some fuel pumps, being cooled by the fuel itself, may react poorly to being run dry. Of course, such pumps are often within the fuel tank itself. But what say you to that concern? I don't know enough about my BF50A (2001?) to have enough knowledge of the matter. I drain its bowls manually before wintering with the little screw and hose setup as per the manual, have swapped its prop, changed its oil, water impeller, drive and trim fluids, cleared "pee hole cloggery" a couple of times, but that's about it.

The BF50A has a mechanical diaphragm fuel pump. It's basically a rubber sheet being pulled up and down by a lever and a couple of one way valves. Not really any cooling going on there. I always ran mine dry at the end of the trip and never had a problem with the pump.

Be Free wrote: ↑Tue Jun 15, 2021 9:54 amThe BF50A has a mechanical diaphragm fuel pump. It's basically a rubber sheet being pulled up and down by a lever and a couple of one way valves. Not really any cooling going on there. I always ran mine dry at the end of the trip and never had a problem with the pump.

I've always just run mine dry in the driveway at the end of the season, then drained each of the three float bowls through the little black hoses it came with into a small container. There's always some gas in those float bowls even after running it dry, which is, of course, why the drains are there.

A brief update.
I did a compression check this evening and it was good. Also checked the spark with a tester and it seemed okay but I replaced the plugs anyway. Then I ran the gas out of the motor. I think Massey was correct that it will turn out to be flooding. We'll see in a month or so for certain.

Cheers

I'll make this the final update. So, the original problem turned out to be flooding, I believe. I learned somewhere that if you crank the throttle to full on, it will overcome the flooding (I think it opens things up to allow more air in). However, I then experienced a situation where it was becoming starved of fuel. I rebuilt the fuel pump. It didn't start immediately but once I properly primed the fuel line, that seems to have solved it. I had to disconnect the fuel line at the pump and prime with the squeeze thing to relieve an air lock in the line.
Thanks to everyone who provided suggestions.