Cheaper Booster Pump for Vapor Lock?

boater2018

boater2018

Member
Feb 26, 2018
148
Boat Info
2000 Sea Ray 210 Sundeck
Engines
Mercruiser 5.0 EFI

Any thoughts on this versus the $800 mercruiser kit?
 
Scoflaw is very correct. Fuel injection needs more pressure and volume. How many years did the original one last you
 
Cheapest way out would be to run the fuel pump return line back to the tank instead of back to the filter
 
scoflaw said:
Cheapest way out would be to run the fuel pump return line back to the tank instead of back to the filter
Click to expand...
Yeah man, I was wondering if EFI vs Carb would make a difference. The issue that I have with running the return line to the tank is accessibility to install the adapter fitting. There is not much working room at all to be able to make the cut and install the adapter. I'll probably end up getting the Mercruiser kit, I just wanted to get feedback for this pump since it was a similar year model engine. I plan to replace the fuel line from the tank to the water/fuel seperator and the anti-siphon valve this evening. Thank you for the feedback.
 
Scott215 said:
Scoflaw is very correct. Fuel injection needs more pressure and volume. How many years did the original one last you
Click to expand...
I know googling can definitely bring up false results, but I thought carbs required higher fuel pressure than EFI. My EFI requires 30psi, I saw someone in another thread online said the carb models required in the 40s. Anyway, I can't find the PSI info for the Mercruiser booster pump, but it seems that it would be like them to not give that info to prevent you from purchasing a similar setup to this as well, but I could be wrong.
 
The guy in the video probably would have been fine if he just moved that existing pump closer to the tank and away from the engine (and eliminated the metal fuel lines). He talks about "backpressure" being an issue but that's not the problem at all.

The most susceptible part of the system to vapor lock is the section that goes from the anti-siphon valve to the pump (and that would include any filters). The pump needs to pull a VACUUM on that section and then push pressure to the carb or fuel injection. The minute it tries to pull VACUUM in a HOT compartment the gas will vaporize and make it MUCH harder for the pump to move ANYTHING. The first thing you might do is check or change the anti-siphon valves, as any additional resistance caused by those valves will make vapor-lock much more of a "thing".
 
boater2018 said:
I know googling can definitely bring up false results, but I thought carbs required higher fuel pressure than EFI. My EFI requires 30psi, I saw someone in another thread online said the carb models required in the 40s. Anyway, I can't find the PSI info for the Mercruiser booster pump, but it seems that it would be like them to not give that info to prevent you from purchasing a similar setup to this as well, but I could be wrong.
Click to expand...
Carbs are all 4-7PSI. Fuel injection can vary, and also depends on where in the fuel injection system you're measuring. Some have a "low pressure" and a "high pressure" pump. Also depends if it's a throttle body injection vs port injection. Port injection rail pressures can be 30-70 PSI.
 
In a carbureated application 6 to 7 lb is all you need fuel injection is in the '30s to say 50 in pounds I think he got it mixed up
 
And direct injection in cars is 1500 to 2000 pounds
 
Some Mercruisers of that era already have a booster pump installed at the factory. It would be located on the starboard side of the engine above the fuel-water separating filter. Your high-pressure pump is installed inside the cool-fuel module located on the engine's port side (way down low)

Assuming you don't already have a booster pump, the carter pump will work fine as a booster, but it doesn't replace your high-pressure pump for your fuel injection. The booster pump needs to be plumbed between your tank and your water-separating filter.

All that said, a booster pump is just a bandaid. The real issue is the vapor lock. Prevent that, and there is no need for a booster pump to begin with. The easiest solution is a check valve plumbed into the coolant line that goes between the cool fuel module and the thermostat housing. This prevents hot engine water from syphoning back into your cool-fuel module during the heat soak period. (It's also a hell of a lot cheaper and easier to install)
 
bobeast said:
Some Mercruisers of that era already have a booster pump installed at the factory. It would be located on the starboard side of the engine above the fuel-water separating filter. Your high-pressure pump is installed inside the cool-fuel module located on the engine's port side (way down low)

Assuming you don't already have a booster pump, the carter pump will work fine as a booster, but it doesn't replace your high-pressure pump for your fuel injection. The booster pump needs to be plumbed between your tank and your water-separating filter.

All that said, a booster pump is just a bandaid. The real issue is the vapor lock. Prevent that, and there is no need for a booster pump to begin with. The easiest solution is a check valve plumbed into the coolant line that goes between the cool fuel module and the thermostat housing. This prevents hot engine water from syphoning back into your cool-fuel module during the heat soak period. (It's also a hell of a lot cheaper and easier to install)
Click to expand...

Yes, that was my thoughts as well. I plan to replace the anti-siphon and the fuel line from the tank to the fuel water separator this evening or in the morning early. The Mercruiser bulletin regarding vapor lock says the booster pump and the check valve help remedy it BUT does not cure the problem itself. Obviously, curing the problem would be great, but there doesn't seem to be a way to know how to do that definitively. So far, I placed some 5/8 heater hose around most of the lines that I could reach fairly well, added the check valve in the water inlet line between the thermostat housing and the fuel pump, did a tune up, and haven't gotten it resolved completely, although I haven't had the severe issues that I had last season. I did nearly get stranded a couple of weeks ago, though, since the lake water temp is so warm right now. I've been working from the least expensive methods up and I'll see what happens after the parts I have now to replace. After that, I might get a mechanic to replace the pickup tube as I'm nervous about breaking something when taking it off. It is on there super tight. After that, IDK what else to do, but go to the booster pump kit, or look again and see if there is some way to route the return line to the fuel fill hose, but from what I remember, it's pretty tight to try and cut to fit an adapter in the space there is to work with. I just thought what's the difference this Carter pump in the video and the Merc booster pump in the kit. The Merc kit installs between the fuel water separator and the fuel pump and also has an inline filter.
 
km1125 said:
The guy in the video probably would have been fine if he just moved that existing pump closer to the tank and away from the engine (and eliminated the metal fuel lines). He talks about "backpressure" being an issue but that's not the problem at all.

The most susceptible part of the system to vapor lock is the section that goes from the anti-siphon valve to the pump (and that would include any filters). The pump needs to pull a VACUUM on that section and then push pressure to the carb or fuel injection. The minute it tries to pull VACUUM in a HOT compartment the gas will vaporize and make it MUCH harder for the pump to move ANYTHING. The first thing you might do is check or change the anti-siphon valves, as any additional resistance caused by those valves will make vapor-lock much more of a "thing".
Click to expand...
Just
scoflaw said:
You should be able to get that adapter installed at the deck pie plate.
Click to expand...
I'll look at that when I'm up there this weekend. Thank you
 
boater2018 said:
Yes, that was my thoughts as well. I plan to replace the anti-siphon and the fuel line from the tank to the fuel water separator this evening or in the morning early. The Mercruiser bulletin regarding vapor lock says the booster pump and the check valve help remedy it BUT does not cure the problem itself. Obviously, curing the problem would be great, but there doesn't seem to be a way to know how to do that definitively. So far, I placed some 5/8 heater hose around most of the lines that I could reach fairly well, added the check valve in the water inlet line between the thermostat housing and the fuel pump, did a tune up, and haven't gotten it resolved completely, although I haven't had the severe issues that I had last season. I did nearly get stranded a couple of weeks ago, though, since the lake water temp is so warm right now. I've been working from the least expensive methods up and I'll see what happens after the parts I have now to replace. After that, I might get a mechanic to replace the pickup tube as I'm nervous about breaking something when taking it off. It is on there super tight. After that, IDK what else to do, but go to the booster pump kit, or look again and see if there is some way to route the return line to the fuel fill hose, but from what I remember, it's pretty tight to try and cut to fit an adapter in the space there is to work with. I just thought what's the difference this Carter pump in the video and the Merc booster pump in the kit. The Merc kit installs between the fuel water separator and the fuel pump and also has an inline filter.
Click to expand...

I'm surprised the check valve didn't solve it. FWIW the booster pump just helps you push the vapor lock (bubbles) through the system, so yeah, not a real solution. IF engine coolant back-flow is the cause of your vapor lock then the check valve does cure it. It completely fixed the issue on my port engine. It sounds like the heat is coming from somewhere else in your case.

Have you ever had an impeller break apart and if so, were you able to find all the pieces? There could be bits of it lodged in your cool fuel heat exchanger big enough to cause vapor lock, but not enough to overheat the engine when running. Shudder the thought, because the cool fuel module is expensive and extremely difficult to get to.
 
bobeast said:
I'm surprised the check valve didn't solve it. FWIW the booster pump just helps you push the vapor lock (bubbles) through the system, so yeah, not a real solution. IF engine coolant back-flow is the cause of your vapor lock then the check valve does cure it. It completely fixed the issue on my port engine. It sounds like the heat is coming from somewhere else in your case.

Have you ever had an impeller break apart and if so, were you able to find all the pieces? There could be bits of it lodged in your cool fuel heat exchanger big enough to cause vapor lock, but not enough to overheat the engine when running. Shudder the thought, because the cool fuel module is expensive and extremely difficult to get to.
Click to expand...
I have had the boat for 6 seasons and have always had the impeller replaced every other season. I haven’t had any issues with it breaking apart. I replaced the fuel pump last season and removed the cool fuel setup when I replaced it. I put water through it with a water hose and don’t remember anything coming out. It seemed to have good flow, so I don’t think it’s the problem.
 
I had someone suggest adding a second blower bringing in air from outside through one of the vent hoses already there and directing it to the cool fuel module, then the existing blower would pull the air back out, creating a circulation affect.
 
scoflaw said:
Cheapest way out would be to run the fuel pump return line back to the tank instead of back to the filter
Click to expand...
I'm thinking I may do this next. I don't think the anti-siphon helped any, although I didn't have any issues starting with advanced throttle. I had guests, so I also poured some water on the lines and fuel pump/cooler areas as well. Anyway, my Sea Ray parts manual that I downloaded says it's a 1.5" Type A, Class 2 fuel hose. If I get the adapter in the link below, I assume that would work? I'm not sure if the hose is 1.5" OD or how that works. I have nightmares of cutting the hose and the fitting not working, then having a cut hose that I can't find a fitting to repair lol. It would be awesome if someone with the same boat had done this and could offer some advice, but I bet that chance is slim to none. I looked at the hose this weekend and it looks like it should be easy to get to after all.

https://www.hardin-marine.com/p-16582-fuel-line-return-to-tank-adapter.aspx
 
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