Honda 115 HP won't start after warm

[FishingInWI]

Just bought a boat/motor with a 115 HP Honda 4 stroke on the back. Issue I'm having, that wasn't disclosed at sale, is the motor won't start after it's been warmed up.

​​​​​​Motor cranks fine, but will not fire up. In addition, last night I had it out, and after cruising around it actually shut right off after it got too warm. Not sputter, just straight cut out. And that's the weird thing to me, the motor runs perfectly fine, with no hiccups. Nothing rough, and at start up, it fires right up and runs great
​great. But once it gets warm, it seems like some switch or possibly the high pressure pump shuts off.

I haven't torn apart the vst yet, but just curious if there is something obvious I should look at before taking it to a professional to diagnose? Only thing I can think is a relay getting warm or the high pretty pump gets warm. But looking for some input from someone who knows more about these things.

Thanks for looking

 

[ahicks]

When I get something like this, I would start at the water pump. You have no idea how long it's been in service, and it should be changed just 'cuz. Same story on the fuel filters, all of them! This, with an oil and filter change, brings you up to date on the service and a base line for your future service needs. It would also eliminate the possibility that any of those items might be the source of your current headache....

 

[FishingInWI]

Update to this... Replicated the issue in the driveway on muffs. Ran it till it got warm, shut it off for 10 minutes, then tried to start it. It pops, then nothing. Just cranks.

So I took off the line running to the fuel injectors and when cranking, it's still sending fuel. Not sure if it's the proper pressure, but the pump is still working.

So I'm looking at something with the spark, is there something that would stop firing when it gets warm? A switch or something else?

 

[FishingInWI]

When I get something like this, I would start at the water pump. You have no idea how long it's been in service, and it should be changed just 'cuz. Same story on the fuel filters, all of them! This, with an oil and filter change, brings you up to date on the service and a base line for your future service needs. It would also eliminate the possibility that any of those items might be the source of your current headache....

Yeah, all filters and engine oil have been replaced. Gear oil will be replaced when I put it away for the winter. I did post an update to my troubleshooting above btw

 

[ahicks]

Wow, missed that by 2 minutes!

Still need to consider the water pump. And while doing the lower fluid, get that prop off and inspect the drive shaft just ahead of the seal to make sure there's no fishing line wrapped around that shaft trying to take your seal out.

Also, after one that gave me fits on a 50hp engine, I'd be suspicious of the block temp sensor. Not the coolant temp, but the block temp. Would be interesting to use an infra red temp gun on that area to see if heat was building up there after shut down.

 

[FishingInWI]

Would the block temp sensor shut down the electronic if it was faulty and thinking it was overheating? I'll look at the water pump regardless though

 

[ahicks]

Yes it can. If the ECU is programmed like the 50-60 hp engines I'm familiar with, it should sound the temp. alarm and drop 500 rpm to try to cool things down first.

I isolated the problem by unscrewing it from the block, then leaving it hang by the wires while running. On mine, that stopped the problem, but I went through hell to figure out why.

If your seller is a dealer, I would get him involved in this ASAP. These things can be expensive to work on. If you just bought it I would think they should at least help out with the repair parts. Maybe they could loan you a service manual for it?

There, you'll find that these ECU's will sometimes record issues. These can be read using beep codes and a series of flashing lights. All that info is in the manual. I'll warn you in advance though, it's entirely possible for that manual to run you through a bunch of diagnostics - without finding the issue. In that case, they simply tell you to try a new wire harness or try a new ECU. Both will run you several hundred bucks.

 

[FishingInWI]

So I did some troubleshooting. Took out a blow dryer and heated up individual components. Thought I had it narrowed down to one of the ignition coils. Started having issues starting, so I was about to order a new one, but figured it wouldn't hurt to be sure. So I kept making sure either one of the coils were warm, and it didn't end up being that...

So I decided to focus on the water temperature sensor. Not sure if what I did was by the book, but it seemed to tell me what was wrong. Ran the motor on the muffs for about 10 minutes, then let it sit and the problem consistently was there. Wouldn't even fire during cranking. So I disconnected the wire from the water sensor and used a wire to jumper the plug. Cranked it and it fired right up and ran. Plugged it back into the sensor, and it wouldn't start again. Did this quite a few times to convince myself it wasn't a fluke, and it seems to be the water sensor is bad, or I'm not getting good water flow. Either way, I'm about to order the sensor, a gasket, and an impeller kit.

Like you said, I need to get every single thing on this motor up to service minimum and get a base line for everything. Hopefully this fixes my issue cause the motor seems pretty solid when it actually runs.

Thanks for the info Ahicks, I'll report back if it's resolved

 

[MattFL]

Great job trouble shooting. It's interesting there was no buzzer warning of an overheat condition, might want to check on the buzzer to be sure it's working. If that Honda is like mine (1999 50HP), if you trim it up too far and turn the key on, it will beep loudly at you. No need to start the motor, turning the key on is enough.

 

[FishingInWI]

Great job trouble shooting. It's interesting there was no buzzer warning of an overheat condition, might want to check on the buzzer to be sure it's working. If that Honda is like mine (1999 50HP), if you trim it up too far and turn the key on, it will beep loudly at you. No need to start the motor, turning the key on is enough.

Oddly, it would buzz at me when I would jumper the plug and get it running. But no buzzer when it was plugged into the sensor. Just wouldn't start. Once I get the new sensor and impeller kit, I'll confirm everything

 

[ahicks]

Right. The injected motors are going to beep if any of the sensors are unplugged, with no chance of starting. Should beep twice when the key is turned on, flash the trouble lights, then those go out and you SHOULD be ready to go.

 

[FishingInWI]

So, I got a new sensor in today, but did not get the impeller kit. Boats dot net sent me an o-ring I didn't order, instead of the kit... Pretty annoyed about that, so I just ordered one off Amazon.

Thing is, the sensor wasn't the fix and I found something else out. Only way I could get the motor started was by actually pulling the sensor out, due to water heating up with it in, and causing pressure. With the sensor pulled, the water would take a bit to move up the side and I could see steam coming out before the water got there. If I allowed the water to continue to flow out, it would cool everything back off, but if I plugged the hole, it seemed like the water wasn't flowing properly and the block got warm within a second or two. Not sure if it's due to a weak impeller or I have blockage in the chambers and water isn't moving correctly. I get water out the pisser valve everytime, and it's cold even though the block is hot as hell.

So basically, it will not start if I leave the water sensor in after it's warmed up, due to pressure building up from water evaporating. As soon as I pull the sensor out, and relieve the pressure, it starts...

I just ordered some outboard descaler off Amazon to run the engine in a barrel with the cleaner, cause I'm assuming water isn't flowing correctly. Am I assuming correctly? Or could it just be a crap impeller? Mind you, I did have the lower unit dropped today, and impeller housing pulled apart in preparation for the kit to come, ended up putting the old one back in to test the sensor. But the impeller looked ok. Held to the shape of the housing, but it didn't look too bad.

 

[ahicks]

Something that SHOULD have been on my list of things that should be serviced when you get a motor, but was omitted, is the thermostat. That could be the source of your evil when it comes to something that might restrict the flow of water.

Too, from my reading, I'm thinking there is some sort of pop off or pressure relief valve that might stick on these bigger engines. I don';t get involved in the bigger engines, just up to 90 hp myself. So I'm a little over my head here and would hate to provide you bad info.

As far as built up crud, often pulling the t-stat cover and t-stat will give you an idea of what the internals look like. You could even remove the t-stat to help diagnose your water flow issue?

I'm with you in the conditions of the vanes. If they're there, they should be able to provide enough water for testing here.

I've had some trouble with boats dot com this year as well. Seems like Covid is really kicking their pants. More so than some of the others. I wish them all the best as they've been terrific in the past. -Al

 

[FishingInWI]

Yeah, my focus is now on the thermostat and the relief valve. My motor does have one in the plate just below the thermostat. I ordered everything needed to pull that plate, along with 2 different thermostats. The one that was in the motor was a 72 celsius, and I ordered that and a 60 celcius.

Tested the thermostat that was in the motor this morning. It was supposed to open at 72c (161f), and it didn't open until over 190f. Which isn't far from boiling... So that could be a culprit of the water almost boiling and building up pressure in the case. But in turn, I was curious to why the pressure relief wouldn't let pressure past. Also, doesn't make sense why I had to relieve pressure to get it to crank back up...

Either way, I'm going to pick up a bunch of vinegar to run through it tonight, along with the descaler when it comes in. I'm not stressing too much about it, even though it's been a bit bothersome. Everything I'm doing and replacing is something that needs to be done regardless. Who knows the last time any of this has been done by the previous owner. Just looking at the boat itself and what I've done on the motor so far, it needed some TLC.

Thanks for the replies, I'll be sure to follow up, for others who may run into something similar.

 

[FishingInWI]

Still waiting for a couple parts for the water cooling aspect, but while the thermostat was out, I ran it in vinegar to try to clean out the passages. Still going to do the descaler, but just wanted to see if the vinegar would break things up. It did, seems to be flowing alot better.

In the process of running and making the problem come back, I discovered the root of all the evil (I believe). I had ruled out some stuff in the past, but last night I found out the high pressure pump wasn't pushing anything, or not enough fuel... I had checked this before, but didn't figure it out at that time.

I broke down the vst and checked everything out, tank was pretty clean, just a bit of debris. Cleaned everything out either way, and tested the pump. It would work intermittently, but didn't tell me exactly that the pump was bad. I wanted to make sure I was even getting 12v to the connector. So I put everything back together, ran the motor and got the problem to show up, and hooked a VOM to the connector from the harness. Turned the key and I had a steady 12v... So... I ordered a high pressure pump.

Wondering though, if I should order a fuel pressure regulator right away too. I'd rather not just slap a bunch of new parts on it and hope something sticks, but I need the motor running top notch by labor day weekend. Got family coming into town... Thinking I'll order one, just to have it on hand, in case I need it now, or in the future.

So that's where I'm at... Didn't expect to be this much of a pain. I know my way around a 2 stroke, this has been a learning experience on how a 4 stroke Honda works.

 

[ahicks]

OK, this may apply to your 115, maybe not. Inside the VST on the output side of the high pressure pump, there's a rubber "grommet" for lack of a better description. If it's not installed properly, it's possible that "grommet" can plug the outlet in the upper VST body, effectively reducing output to a dribble.

On another forum, several of us (5 and counting just this season) with smaller 50-60hp injected engines have tracked fuel supply issues to this grommet after an incredible amount of troubleshooting. It's a really crummy design that's very well hidden. I just tripped across it while messing with an erratic motor of my own. I would have fuel pressure, then I wouldn't. I actually wired the pump to come on with the key switch to help troubleshoot. Finally, one time it was running, then quit while running in a barrel. I could hear the fuel pump running. So I disconnected the fuel line at the rail, no pressure. Removed the high pressure fuel filter, and STILL no pressure (pump still running!)! So I pulled the VST down for the 3rd or 4th time. There's only an inch from the output side of the pump to the high pressure filter, and the ONLY thing that could possibly block it was this grommet. That's when it dawned on me what was happening. A couple of quick cuts with a #11 x-acto and that possibility was eliminated. Reassembled and everybody lived happily ever after!

When "re-installing" the high pressure pump, I think it's normal to push the grommet into the upper VST body, then push the pump into that grommet and secure the pump with it's mounting screws. The issue is, as the pump is being pushed into that grommet, there's nothing to keep that grommet from sliding further into the VST body, and blocking off the passage leading to the high pressure fuel filter.

Later, I figured the "right" way to install the grommet, is to slide it on to the fuel pump outlet, THEN slide the fuel pump into the cavity in the VST housing and secure. That would eliminate any chance of that grommet going in too far.

4 strokes no harder to work on. They just require more patience. I think they're worth the extra trouble myself. People LOVE them, myself included! -Al

 

[FishingInWI]

Root of all my problems did in fact end up being the high pressure fuel pump. It would work intermittently, so it led me to parts that weren't actually the problem. When I turn the key now, I can hear the pump prime up the rails. Could barely hear the old pump, and all it would do when it acted up, wasclick.

So basically, if someone is having intermittent running and starting issues, check to see if you can hear the high pressure pump spool up in the vapor separator tank. If you can't hear anything, check for voltage at the connector when you turn the key to the first click, then voltage again when you're cranking.

I came into this knowing quite a bit about 2 strokes. In my opinion, after all this troubleshooting and learning more about this particular 4 stroke, they're way less complicated. Also, Honda makes a very solid motor, with ease of maintenance. I used to be a jet mechanic in the Air Force, and I'm amazed at how much thought Honda put into building their product, the hardware used, and the placement of everything. Nothing was terribly hard to get to, or work on.

To those who commented, thank you. You helped me troubleshoot and learn more about Honda's/4 strokes