Mercruiser 3.0 started twice perfectly overfilled the gas now won't start

[mercruiser_3.0]

Hello all,

I recently bought a Bayliner capri with a mercruiser 3.0 alpha one. I took it out with the previous owner it ran like a top. Brought it home, hooked it up to water, it started up great. Filled up the tank and went to the lake and it wouldn't start. When I got in the boat at the lake, I stepped by the gas tank and gas came out of the vent on the back. I was like ok maybe too much gas oops. I have not been able to get it started since. I checked the spark and we have great spark on all four plugs. I took the top off to look at the carb and it seems to have a lot of gas in the carb like it's flooding or something. Any help on what to do next? I drained some gas out and it still won't start.

 

[Chris1956]

Sure, just like those 60's cars needed to clear a flooded engine. Use the screwdriver to prop the choke open. Set the throttle to full in neutral.

Crank it until she fires, and then pull back on the throttle quickly to stop her from high RPM.

 

[Chris1956]

Gee, and fix the deck near the fuel tank.

 

[cyclops222]

A NON vented gas cap can over pressure the carburetor float and needle tip parts. Get lucky
Get a vented gas cap.

 

[Bondo]

A NON vented gas cap can over pressure the carburetor float and needle tip parts. Get lucky
Get a vented gas cap.

Ayuh,...... Boat gas tanks already have a separate vent system,.....

 

[cyclops222]

If it is working correctly. And a gas saving person has not modified the system to save money.

 

[mercruiser_3.0]

A NON vented gas cap can over pressure the carburetor float and needle tip parts. Get lucky
Get a vented gas cap.

So it would probably be best to take the carburetor off and check the float and needle?

 

[mercruiser_3.0]

Sure, just like those 60's cars needed to clear a flooded engine. Use the screwdriver to prop the choke open. Set the throttle to full in neutral.

Crank it until she fires, and then pull back on the throttle quickly to stop her from high RPM.

I have cranked it until one of my batteries died lol. I didn't do it all at once. I didn't want to make the starter crank that long but over a couple of days I cranked it a lot. My choke button is a bit wonky, I may need to check to make sure it is working properly.

 

[ESGWheel]

Sounds like there are a few things going on here and maybe more.

If the engine was flooded out by ‘pressurizing’ the gas tank and its been a day or so, that should have evaporated by now. So, let’s start at the beginning.

Post filing your tank and noticing gas spitting out of your vent when stepping on or next to the deck where the tank is indicates a possibility rotted out deck.

Why would it flood the engine? I assume this carb’ed engine has a mechanical fuel pump. These types of pumps will pass gas thru them if under some slight pressure > i.e. if you push gas into the pump inlet, it will readily flow thru the pump. And when that gas was getting pushed out the vent, its possible that it also pushed thru the pump.

Now normally, the needle / seat and float device in the carb would preclude more gas getting in UNLESS the incoming pressure is too high, or the needle / seat and float device is not working properly. More then likely it is working fine based on your excursions prior to buying. Thus, it was an over pressurization which your seeing lots of gas in the carb supports.

But still not starting and been at least a day. Hmmm…..

Here are my suggestions:

• Obviously charge the battery, once done and all is good do not forget to check its water level.
• Pull out the plugs. Do they look wet? Leave out the plugs reguardless.
• Open the throttle to max (Wide Open Throttle or WOT)
• With the spark arrestor off, use a screwdriver or stick to hold open the choke plate
• Come back the next day (now the battery is charged) and put it all back together and try and start normally. This will allow time for any flooding gas to evaporate and give it a wide path to do so.

Post results either way b/c if it does not start, lots of good folks here that can help work thru that.

 

[mercruiser_3.0]

Thank you for this detailed explanation! I will do all of that. I have checked the plugs and they were wet for sure. I will pull them and let it dry out.

Yea the floor was rotted when I bought it but I didn't think it was a huge deal. I was going to replace it soon.

Sounds like there are a few things going on here and maybe more.

If the engine was flooded out by ‘pressurizing’ the gas tank and its been a day or so, that should have evaporated by now. So, let’s start at the beginning.

Post filing your tank and noticing gas spitting out of your vent when stepping on or next to the deck where the tank is indicates a possibility rotted out deck.

Why would it flood the engine? I assume this carb’ed engine has a mechanical fuel pump. These types of pumps will pass gas thru them if under some slight pressure > i.e. if you push gas into the pump inlet, it will readily flow thru the pump. And when that gas was getting pushed out the vent, its possible that it also pushed thru the pump.

Now normally, the needle / seat and float device in the carb would preclude more gas getting in UNLESS the incoming pressure is too high, or the needle / seat and float device is not working properly. More then likely it is working fine based on your excursions prior to buying. Thus, it was an over pressurization which your seeing lots of gas in the carb supports.

But still not starting and been at least a day. Hmmm…..

Here are my suggestions:

• Obviously charge the battery, once done and all is good do not forget to check its water level.
• Pull out the plugs. Do they look wet? Leave out the plugs reguardless.
• Open the throttle to max (Wide Open Throttle or WOT)
• With the spark arrestor off, use a screwdriver or stick to hold open the choke plate
• Come back the next day (now the battery is charged) and put it all back together and try and start normally. This will allow time for any flooding gas to evaporate and give it a wide path to do so.

Post results either way b/c if it does not start, lots of good folks here that can help work thru that.

 

[Scott06]

Yea the floor was rotted when I bought it but I didn't think it was a huge deal. I was going to replace it soon.

So the floor is rotten enough to compress the gas tank and push fuel out the vent?

Floor usually rots after the stringers and transom rot, or is this a carpeted cover over fuel tank

 

[mercruiser_3.0]

So the floor is rotten enough to compress the gas tank and push fuel out the vent?

Floor usually rots after the stringers and transom rot, or is this a carpeted cover over fuel tank

This is a carpeted floor tank. It is in between the seats. I honestly never had one like this so I was like wait where does the gas go and he showed me it was under some marine plywood that he used for the soft spot lol.

 

[ESGWheel]

Here is what I found on the web for a 1750 Capri which is same as or close to what you have. The tank is forward of the engine and between the seats as you expressed. See picture. Sounds like the Previous Owner (PO) simply laid down a piece of ply on top of a rotted deck.

While the focus of this thread is to get you running, I strongly urge you to proceed with caution post that. Let me explain: as Scott expressed the deck is usually only part of the story. While I am not the expert on this, I believe you boat has 2 stringers running down the length of the boat just on either side of the center line and are what the motor is mounted to as well. In addition to the dangers of a rotted deck, if those stringers are also compromised your engine could literally rip out of its mounts. This is akin to a rust rotted out frame on a car, of which we have plenty of here in MA. Not trying to scare you but this could be dangerous.

My strong suggestion: start a new posting on the forum “Boat Restoration, Building, and Hull Repair” and provide boat info, history, and current situation of ‘rotted deck’ and ask the question: How best to determine the condition of my transom and stringers, in general need to know if my boat has its integrity or is perhaps unsafe. This will probably involve drilling. And if uncomfortable with that, a good marina or marine surveyor can help as well. Please, do not ignore figuring if your craft is safe. Thanks.

 

[cyclops222]

Did you ever remove the gas cap ? To remove the pressure ? If you screw the cap back on tightly ? It may build up pressure again. And again.
Leave the cap loose. Otherwise..... When you remove the carburetor. The tight cap will cause gas to pour out of the disconnected fuel line end.

 

[mercruiser_3.0]

Here is what I found on the web for a 1750 Capri which is same as or close to what you have. The tank is forward of the engine and between the seats as you expressed. See picture. Sounds like the Previous Owner (PO) simply laid down a piece of ply on top of a rotted deck.

While the focus of this thread is to get you running, I strongly urge you to proceed with caution post that. Let me explain: as Scott expressed the deck is usually only part of the story. While I am not the expert on this, I believe you boat has 2 stringers running down the length of the boat just on either side of the center line and are what the motor is mounted to as well. In addition to the dangers of a rotted deck, if those stringers are also compromised your engine could literally rip out of its mounts. This is akin to a rust rotted out frame on a car, of which we have plenty of here in MA. Not trying to scare you but this could be dangerous.

My strong suggestion: start a new posting on the forum “Boat Restoration, Building, and Hull Repair” and provide boat info, history, and current situation of ‘rotted deck’ and ask the question: How best to determine the condition of my transom and stringers, in general need to know if my boat has its integrity or is perhaps unsafe. This will probably involve drilling. And if uncomfortable with that, a good marina or marine surveyor can help as well. Please, do not ignore figuring if your craft is safe. Thanks.

View attachment 408699

Thanks for the help. I will not even worry about starting it right now until I take the tank out and fix the floor and stringers.

 

[mercruiser_3.0]

Did you ever remove the gas cap ? To remove the pressure ? If you screw the cap back on tightly ? It may build up pressure again. And again.
Leave the cap loose. Otherwise..... When you remove the carburetor. The tight cap will cause gas to pour out of the disconnected fuel line end.

I do tighten it every time I will leave it a little cracked.

 

[ESGWheel]

First off, your gas cap is not the issue. And I am glad you are investigating the rot issue. I found this on the web of doing a restore of a Capri link. He has a whole series of doing a restore. I only watched the episode of the gas tank removal. Frisco Boater (link) also has the best restoration series I know of and I did watch all of that. I provide these to give you a sense of the activity you are about to take on as it can be really extensive > go after the decking and end up needing to do the stringers and then the transom… In a way I envy you as I wish I had the youth and strength to tackle such a job. And it’s a great excuse to buy a bunch of cool tools!

Again, please keep posting on the appropriate forum, there is a lot of experience out there you can take advantage of!

Good luck!

 

[mercruiser_3.0]

First off, your gas cap is not the issue. And I am glad you are investigating the rot issue. I found this on the web of doing a restore of a Capri link. He has a whole series of doing a restore. I only watched the episode of the gas tank removal. Frisco Boater (link) also has the best restoration series I know of and I did watch all of that. I provide these to give you a sense of the activity you are about to take on as it can be really extensive > go after the decking and end up needing to do the stringers and then the transom… In a way I envy you as I wish I had the youth and strength to tackle such a job. And it’s a great excuse to buy a bunch of cool tools!

Again, please keep posting on the appropriate forum, there is a lot of experience out there you can take advantage of!

Good luck!

Thank you for the videos! I have the best father in law that likes to help with projects like this. With these videos I think we will be able to handle the stringers and rot. I already found a couple others to reference too. I'll be back and post the finished whenever that gets done.