Starboard Engine Slow Crank, No Start

[Beachbummer]

You more about it than me by a long shot...thinking out loud... Can you get to a point where you can turn both engines by hand and compare? There is the possibility that something is indeed wrong separate from the starter that is causing this engine to be harder to turn. Stuck valve? No clue what else it could be? But you have isolated the starter circuit and it behaves as if the engine was indeed harder to turn.

 

[Kernel]

You more about it than me by a long shot...thinking out loud... Can you get to a point where you can turn both engines by hand and compare? There is the possibility that something is indeed wrong separate from the starter that is causing this engine to be harder to turn. Stuck valve? No clue what else it could be? But you have isolated the starter circuit and it behaves as if the engine was indeed harder to turn.

I've haven't been able to turn either impeller by hand during this troubleshooting process. Which itself is kind of weird because I do recall having done it a year or so ago when I sucked up a tow rope. Killed the engine as soon as it went under the boat so it didn't do any damage, but it took me a good 10 minutes to get it unstuck and I want to say I turned the impeller by hand to free the rope, but now I'm honestly not sure. Should I be able to turn the impellers by hand?

 

[Beachbummer]

I think there is a plastic cover on the engine rear that you can remove and then hold the intermediary shaft in your hands, and that is a more likely spot for turning the engine over by hand. Someone else may come with more experience on it, I have not done that before.

 

[Kernel]

I'm wondering if maybe this isn't a starter issue, but what if it is a generator/electrical issue? The battery checks out, the relay checks out, the starter checks out, all of the wiring to and from the starter checks out. I'm not sure how the whole electrical system works, but at some point after the engine is started the generator sends power back to the battery. During start something prevents the current from flowing from the generator to the battery... right? Thinking of it like water, what if while the engine is trying to start, the generator is at the same time trying to send power back to the battery pushing back on the current coming from the battery and prohibiting the engine from starting? It would, in my mind at least, explain why the engine will start when I have the battery booster sending additional amperage to the engine and why the voltage on the starboard engine fluctuates significantly more than the port engine during cranking. Just thinking aloud right now, but if anyone knows about electrical systems, let me know if I'm way off base here.

 

[Kernel]

Answering my own question after some research. The regulator/rectifier (which is what converts AC power from the stator to DC and then sends it to the battery) is mounted to the header that I removed to get to the starter.... so my guess is clearly incorrect. I am thinking more anymore about amperage though. My battery is a 400 CCA Lead Acid battery, most pictures of batteries I am seeing on the forums are 800 CCA. Not sure what "stock" is, research continues.

 

[Cobra Jet Steering LLC]

It is your pump liner swelling up and dragging on the impeller very common after they sit a while spray some wd40 in the pump around the liner and impeller and keep trying to start it usually it will turn slowly at first and then start, you need to replace the liner section of the pump.

 

[Kernel]

It is your pump liner swelling up and dragging on the impeller very common after they sit a while spray some wd40 in the pump around the liner and impeller and keep trying to start it usually it will turn slowly at first and then start, you need to replace the liner section of the pump.

Good thought, but right now I’ve got the impeller, headers, and air box all removed.
Also, just dropped in a brand new battery, this one with 800 cold cranking amps. No change.

 

[Cobra Jet Steering LLC]

well if the pump is off and it still won't turn over there is an issue inside the engine can you remove the plugs and try to turn the engine from the P T O on the back of it

 

[Kernel]

well if the pump is off and it still won't turn over there is an issue inside the engine can you remove the plugs and try to turn the engine from the P T O on the back of it

I’m afraid that you’re right and the problem is inside the engine. It does turn, just about a hundred RPM slower than the port on crank and getting it started is next to impossible. Trying to eliminate all of the easy stuff before I breakdown, drive up to San Antonio, and drop it off with Yamaha.

 

[Cobra Jet Steering LLC]

ok and you checked to be sure the oil is not overfilled or smells like gas, a bad injector can do bad things to the engine and the oil level

 

[Kernel]

ok and you checked to be sure the oil is not overfilled or smells like gas, a bad injector can do bad things to the engine and the oil level

I haven’t done that actually. I did pull the dipstick to check the quantity/quality of the oil and it looked good. Don’t remember smelling any gas in it. It’s definitely not overfilled. I typically change it at the beginning of July every year, but it’s been down since late June now. I’ll have to take a closer look at it.

Both engines seemed to produce equal power for the same throttle setting prior to the break-down. Not sure if that means an injector issue is unlikely, but there were no indications anything was wrong prior to this.

Going to order a YDIS this week. Didn’t notice any codes, but it would be nice to check some stuff out.

 

[Cobra Jet Steering LLC]

I would also pull the plugs and take a look at each one, they are the report card of your engine and that may point you in the correct direction.

 

[Kernel]

I would also pull the plugs and take a look at each one, they are the report card of your engine and that may point you in the correct direction.

Pulled the plugs, didn’t measure the gap, but they appeared normal.

 

[Cobra Jet Steering LLC]

ok and they are all firing,

 

[Kernel]

ok and they are all firing,

Yep

 

[Kernel]

Update

Finally took to boat up to the Yamaha dealer in San Antonio. Turns out there is low compression in all cylinders on the starboard engine, which I can believe. Apparently normal compression is 150psi and the cylinders are reading between 40-80psi. The dealer says the low compression is a result of corrosion, and is therefore likely NOT covered by the Yamaha Extended Warranty (YES). This I cannot believe.

Here is why I simply cannot accept that the low cylinder compression is a result of corrosion.

1. I'm OCD AF when it comes to cleaning my boat and the engines after every use. We typically use the boat two days a weekend during the summer months. We rinse the engines with fresh water every Saturday, and salt away every Sunday. We also rinse the entire boat after every use, and wash with boat wash every other Sunday. My boat is only four years old and in amazing shape.

2. There were zero symptoms leading up to the first time the engine would not fire up. If corrosion were the culprit there would have been symptoms leading up to the complete failure of compression in all cylinders. Misfiring, running rough, hard starts leading up to this, something, but there were none. On the day it failed to start, it had started up completely normally and ran like a champ initially. We even stopped and started the engines several times as we followed near a pod of dolphins. It was only after a several hours at the beach that it would not start, with the slow crank as the only noticeable symptom.

3. Slow cranking, as far as I know, is NOT a symptom of low compression. If there were only low compression due to corroded/leaking seals the engine should be cranking FASTER than normal, not slower. I'm no mechanic (at least not anymore, former helicopter mech turned pilot) and most of my knowledge of engines is related to turbine engines, but this isn't the most complicated principle to understand. Suck, squeeze, bang, blow. If compression is low, there is less resistance during the squeeze. Less resistance means faster reps and because air escapes the cylinder the mixture is too rich and does not ignite.

4. I pulled the spark plugs myself and did not see any corrosion on them whatsoever. I used to work on and now fly aircraft that spend a lot of time very close to the water. I know what corrosion looks like and what it can do, that's one of the reasons I am so very OCD about keeping my boat in tip top shape. The rep I spoke to was in service had not seen the speak plugs himself, but said his mech said there was corrosion on the spark plugs. I'm just not buying that. I'm not calling him a liar, but I'm guessing it's a common cause of low compression and I think he may have just said that when I started asking questions.

I'm sure there is more I am forgetting, but it's 4am and I am awake because this popped into my OCD mind at 3am and couldn't get off of it. Long story short, I am looking at a "short block" replacement, and it's going to get expensive if not covered by YES. I'm open to critiques to my line of thinking. I don't know much about timing, but from what I've read previously this screams broken timing chain to me. I do know that timing chains were a common point of failure on earlier model engines, but I thought it was something that Yamaha had addressed and corrected with a thicker chain.

More to follow as the situation develops.

 

[Cobra Jet Steering LLC]

First thing I would do is my own compression test be sure the throttle is OPEN when doing that to allow proper air into the cylinders, compression 80 or above is the minimum needed for the engine to run. you could have a warped head or stuck or bent valves or a timing chain out of time or stuck rings, to check for stuck rings do a second test using oil in each cylinder and see if the compression goes up considerably from the dry test. You may also have cracked heads around the valve seats placing 5 valves in an aluminum head makes for pretty thin aluminum between the valve seats. You can also look in the cylinders at the top of the pistons, clean and shiny usually means water in the combustion chambers and is very bad. The plugs would also have had a silver color to the ends as well it is not a common issue with 4 stroke engines though.

 

[Kernel]

First thing I would do is my own compression test be sure the throttle is OPEN when doing that to allow proper air into the cylinders, compression 80 or above is the minimum needed for the engine to run. you could have a warped head or stuck or bent valves or a timing chain out of time or stuck rings, to check for stuck rings do a second test using oil in each cylinder and see if the compression goes up considerably from the dry test. You may also have cracked heads around the valve seats placing 5 valves in an aluminum head makes for pretty thin aluminum between the valve seats. You can also look in the cylinders at the top of the pistons, clean and shiny usually means water in the combustion chambers and is very bad. The plugs would also have had a silver color to the ends as well it is not a common issue with 4 stroke engines though.

Thanks for the tips! Boat is still up in San Antonio and I'm down in Corpus, but called the dealer this morning to speak to them about it. They're going to compression test the port engine to see where it's at. If the compression in the port is fine then it is pretty clear that the cause of low compression in the starboard engine is not due to lack of preventative maintenance resulting in corrosion. He agreed that low compression should result in higher RPMs on crank, not lower, and said he would ask the mech if he fogged the cylinders prior to the compression test to make sure they were not fuel washed. I'm still thinking it is a timing issue, but will know more later today.

 

[ReelFishingSWFL]

I have the same problem except it’s not low compression I have 180 psi in all just slow cranking. I checked everything you did any ideas?