Motor trouble - ever hear of this? (for the gearheads and I;m not one)

[So_I_Ski]

@BraceMaker it's a 2006 Gekko with a 350 chev PCM. @Orlando76 Just got home from skiing with a buddy and too late for pics but I will check the motor tomorrow for the serial number. And it is 100 percent an electric fuel pump mounted on the bottom right hand corner with positive and negative posts at the bottom. The model number is 4601hp and I believe that it is a Carter pump. As the fuel exits to the carb it goes up an 8 inch metal line with an rh bend followed by an 8 inch rubber fuel line with a fuel regulator in the middle which has a dial with options from 1 to 5.5 with half increments. I have removed that and taken it apart and it only has a small rubber diaphragm which is whistle clean. It had been set at 3.5. Then another metal line that bends left again and into the front of the carb. Just as it enters the carb body there is a very small screen hidden inside the connection which I removed to check over a week ago and that was also clean. Regarding the fuel pump as I said earlier I replaced it with an identical Specter but no change so I took that back. I had intended to remover the fuel pickup today but got derailed so I'll try that tomorrow. Thanks again guys for all the intelligent input.

[elr]

Deleted

[Orlando76]

Well the 4601 was used on PCM engines, as others too. @BraceMaker I too wondered about the possibility of it being converted to a carb but since he’s the original owner surely he’d remembered something like this. Not much info out there on Gekkos from 2006. A “quoted brochure” I found online listed the 270 hp 350 Merc as base power with the 350 PCM Apex being the upgrade with the Apex of course being efi. The 270hp Merc, all, appear to be carb and Merc loved electric fuel pumps with carbs. Both motors ran the PCM transmission. As they’ve proven in past, boat manufacturers will pull power plants from anybody that will give them a line of credit when things go south and change flavors up in a heartbeat to move a boat, not following original intentions/brochures etc. And PCM offered a 350 carb during that time, I thought only as a bobtail repower boats like Shamrock etc. in fact they still do, in the Crusader line. I believe Gekko was floundering in 06 while the original owner was gone for a period? Gekkos aren’t popular boats and this one is definitely a one off boat. So back to it shutting down at 2600... Surely the 1-5.5 doesn’t indicate psi? Meh, take a pair of lineman’s pliers to both bowls and give it a medium whack square on the back side and see if it dislodges something sticking, I think that’s been mentioned. And to go along with everyone else, an auxiliary tank hooked up to that fuel pump would eliminate sticky anti siphon valve. Another is 2600 is common speed for engine management to send into limp mode but at 7-10 seconds?

[DW]

This should not be the root cause as not changed prior to the problem, but does the carb sit level (mounted on a wedge plate) to the water? If not, perhaps the floats have a better chance of sticking or jamming and the float bowls would carry less fuel.

 

Another question, did you do anything just before the problem started, if yes go back and change it back to see if that induced the issue (my favorite troubleshooting method, what did 'I' do to mess this thing up...).

[Jetsetr]

Having the boat run with no load on it would not recreate the issue as mentioned...

 

Haven’t seen a electric pump on a carb motored ski boat (not saying they didn’t do that). USUALLY a electric pump has an external regulator, but I’m more familiar with race pumps. If the fuel pressure was too high it would pop the needle off the seat and cause flooding, not a lean condition.

 

Too much fuel isn’t the issue.

 

Crank the regulator all the way up and see what happens....not going to hurt anything...3.5 is a little low in my opinion...

 

I might have to come out there and fix your boat! Still fly for free since I retired from an airline...

 

 

[So_I_Ski]

@Orlando76 you are correct in a number of things about the origin of my boat and it being a "one off", kinda. Mark Overby who was the original owner of the hull had Centurion build the boats in their plant from inception. Then in 2005 he sold the mold to IMAR Group out of North Dakota. From what I understand they were a runabout manufacturer and knew little about building a tournament boat. A good friend of mine was the Gekko distributor here for years and he ordered the boat for me and chose to go carburated instead of EFI to save me some money so in that sense it may have been the only carburated boat they sold out of the limited number they did make. Anyway, the IMAR Group only made Gekkos for a year before the crash. And no one suggested whacking the carb up the back side so I'll give that a try. @DW I did not do anything prior to the onset of this problem and it had been starting and running great. @Jetsetr I tried cranking up the fuel reg to 5 but it made no diff. And you would think that with everything I have eliminated combined with the suggestions from you guys that the mechanic who is coming by on Tuesday should solve the problem pretty quickly if I don't get it myself. And what a great perk for you to be able to hop a plane and go wherever you want. Where do you live? I'm in Kelowna BC, semi-retired and work for myself. Kelowna is on Lake Okanagan in southern BC but a group of us drive 2 hours to a magical lake where we can ski on glass every day so come on up.

[RichardDoane]

Mercruiser would not have forgotten a fuel filter. Take a better look. Is it part of the electric fuel pump

[So_I_Ski]

@RichardDoane it's a PCM not a Merc.

[Orlando76]

Well, front side and back side. Back side shouldn’t be coming in at 2600 rpm. Must’ve been a bobtail PCM. The SN would be nice to confirm a couple things. Nice to see a carb boat in this day. So many carb haters out there but this summer on the forums the GT40 PCM problems were posted 10:1 compared to carb.

[So_I_Ski]

@Orlando76 there is a small aluminum PCM plate attached to the top of the tranny. Stamped on that plate is the model #IRM40-11 and a Serial #20069684.

[So_I_Ski]

@Orlando76 OOPS, that was the tranny info. The motor info is model # 03-572-01 and the serial number is 465076

[Brewski]

Could be as simple as the fuel filter. On quadajets they are at the inlet to the carb....

[Rednucleus]

The 3.5 pressure is what I expect for a carb; totally different beast then fuel injection. Just need to keep the bowls full, not supply a hi pressure fuel injector stream. Do you know what pressure the pump makes - I don't think our Sportster has a separate pressure regulator. If it's a low pressure pump try bypassing the regulator. My guess is the regulator is your problem - any way to test pressure?

Note - the 4601 hp is listed with a working pressure of 6psi - should be able to bypass regulator as a test w/o overwhelming the floats. Then if it's fixed or runs rich you know the regulator is the problem. If no change it's in the carb.

[So_I_Ski]

@brewski only fuel filter is exiting the fuel tank & I changed that. At carb inlet only a small thumb sized screen and it's clean. @Rednucleus I pulled apart that fuel reg and it's whistle clean and such a simple device with a small diaphragm that it can't be the problem.

[Rednucleus]

@So_I_Ski humor me, bypass it or test pressure and see what happens - it's an easy test and costs nothing. Sometimes when I know something can't be the problem I get a surprise.

[Orlando76]

@Rednucleus I agree with ya. That pump has a working pressure of ~6-10.5, pushing the high limit for a carb. But I think we can agree that if his pressure was too high he’d fall on his face after warm up and have no low end. Instead he has opposite.

 

@So_I_Ski not a PCM expert just a hobbyist with their parts and with what motors offered and marketed and what went where etc.

I expected a number real close to this:

P_LAPRL123D 465076

The D being the key, and the “46” confirms the 2006 year. It appears to have been a packaged motor, not a bobtail. When I look up the “03-572-01” I’m coming up with........ MPI 5.7.

[Rednucleus]

@Orlando76 My theory is the pressure is too low, not too high and so I would bypass the fuel regulator to see if it's the problem - and I would verify the pressure from the pump as well - both are quick/easy/inexpensive checks before digging in to the carb

[So_I_Ski]

@Rednucleus I would love to humor you but my problem is that it means getting another piece of fuel line to fit where the gauge is and then dragging the boat to the lake to do that test. And how do I test the pressure - do I buy a gauge? On top of all that, having opened that gauge I find it hard to believe that it is faulty. Logically, my problem is related to something that has broken down in stages albeit quite quickly. And you are correct that the number I gave you corresponds with my specs in the manual which indicate that I have a 5.7L MPI engine. Coming back to the fuel pump, when I replaced it with a new one, the symptoms remained identical. So again, looking at it logically, how likely is it that the new pump would behave in precisely the same faulty fashion. @TEL I have just finished pulling the fuel pickup and the screen on the bottom is clear and clean so one more possibility eliminated. I guess I am down to a vacuum leak or collapsed float bowl in the carb as per @Orlando76 if it's fuel related. Otherwise maybe ignition is the only thing left? Anyway I will keep you all posted when and if the mechanic solves the riddle on Tuesday. Thanks again for all the input. It's been an education if nothing else.

[Rednucleus]

@So_I_Ski I agree I think the pump is fine. If I was to test pressure I would rent a gauge from the local auto parts store and hook it after the regulator & put 12v to the pump. You mentioned you were able to take the regulator apart - could you take out the innards and re-assemble so it is just an empty shell. That would be the same as bypassing it and show if it's the problem?

[So_I_Ski]

@Rednucleus yes I could take it apart and remove the innards but if you saw it you would see that there is only one part to remove and that part is just a thin rubber diaphragm about an inch in diameter and it looks brand new. The reg itself is only about 2" in diameter and only consists of a spring loaded dial putting very slight pressure on that diaphragm as you turn it from 1 to 5. When I removed it and then put it back together I ran a low stream of compressed air thru it while turning the dial one notch at a time and the pressure of the air exiting the other side only varied slightly. So it works but I don't think it could ever have the significant effect that is plaguing my motor. Particularly when, as I say, it looks brand new and the only parts inside are a small spring exerting slight pressure on a thin rubber diaphragm. For it to have worked fine for years and then to have failed there would have to be at least some physical evidence of that failure within the unit and there is none. My next and last attempt before the mechanic arrives tomorrow will be to take it down to the lake and try tapping the carb as per @Orlando76 suggestion.

[Keith_Menard]

SO WHAT WAS IT!?!?

[So_I_Ski]

For those who were curious, I wasn't holding out on you. I just couldn't update because I headed back to the lake which has no internet and got home two hours ago. Now you're not going to believe what happened hours before I left. Last Tuesday the mechanic showed up and before taking the boat for the lake test he asked me to start it in the driveway whereupon he focused on my fuel regulator suggesting that was the problem. I had already informed him that couldn't be the problem as per my last report to you guys above. he was reluctant to agree with me but we took it to the lake for the test run. It took about 30 seconds before it started acting up and at that point he determined that it was definitely my primary coil that was failing and that it wasn't fuel related. He proceeded to order a new distributor and when it arrived on Thursday morning he came over and installed it. Then back to the lake and guess what? NO CHANGE!!

 

Now WTF? At that point he said that if we headed back to my place and grabbed his fuel pressure gauge from his car we could test the pump. Now I had told him that I had tried a new pump and it didn't solve the problem. We were packed and ready to head to the lake and I really didn't need my boat but he assured me it would only take 10 minutes to test the pressure. Anyway, he installed his gauge and low and behold, within 10 seconds the pressure starting dropping quite quickly and in another 10 seconds it was down to zero on his gauge. Now the new pump I had tried was a Spectra since the auto parts place didn't have the Carter pump that I have. The mechanic and at least three other experienced motor guys have all told me that if you put in a Spectra part you can expect one of three to work. So real shit parts. However, it still seems odd to me and one of those other guys that the Spectra would act faulty in precisely the same fashion as the Carter when most commonly, a fuel pump either works or doesn't work at all.

 

While I was at the lake I talked to one of those guys and he said that I can now do a very simple test to confirm that it is either the pump or something else that is just shutting down the pump when it goes over 2600. He told me to hot wire the pump directly to the battery and if if still shuts down it's definitely the pump and if not it isn't. So within the next day or two I will try that test and go from there so stay tuned.

 

[Jetsetr]

I like good Scotch...18 yr Macallan is fine....

See my Aug 10th post...

Will share!

@Horton still owes me a bottle from the submarine ski boat that threw the rods out...was right one that one too.

(All in jest of coarse ;) ;) :# )

[So_I_Ski]

@jetsetr funny guy and I like black Russians myself but I won't know for sure until I hot wire that pump. Remember, that the first two things I did was install a new fuel filter followed by a new pump so even though the symptoms indicated a fuel delivery issue, who would think that a new pump would be faulty in precisely the same strange manner as the existing one? I guess that's becoming more common these days with crappy parts from China. Boy does that make diagnosing mechanical and electrical issues more difficult in the future with unreliable replacements. I hope that a lot of guys read this thread just so they are aware that the new part they install might also be defective.

[Rednucleus]

I think I am entitled to a finger or two of that nice scotch as well :)

[So_I_Ski]

You're a bunch of damn alcoholics posing as waterskiers! :)

[LeonL]

Buy yourself a Holley fuel pump and move on. I would also suggest that you power it via a relay and not just powered from the ignition.

[Jetsetr]

@Rednucleus agreed!

 

[skier2788]

@So_I_Ski I have only done a quick scan of this thread but if you are running an electric pump with a carb they usually run a Murphy switch. It is an oil pressure switch back by the distributor. The idea is that you do not want your fuel pump to run while the engine is not but the key is on. It would over run the floats in the carb and flood the engine. I have seen the Murphy switch fail a couple of times on a buddies 04 Moomba. Does pretty much what you are describing.

[SM]

This has happened to me. Dirty pickup in the fuel tank.

[So_I_Ski]

@SM thanks but suggested by @TEL which I promptly did on Aug 11. @skier2788 thanks and I will go looking for that switch.

[eleeski]

@So_I_Ski How did you inspect the in tank pickup filter? I did an old 66 Mustang and there was a hole built into the tank to access the (horribly clogged) filter. But my 79 American Skier has no way to access the filter. Blowing backward got a nice reverse flow but the flow was restricted again on forward flow. I'm running an outboard tank now with no issues (similar problems to yours before). My scotch solution to your problem is betting on a dirty tank pickup.

 

Note, my check valve at the top if the tank was sticky. Bypassing that didn't work for long.

 

When I ran carbs, I never did much troubleshooting. I just replaced the carb with a new one. Rebuilt carbs never lasted long. I'd get a few years out of a new carb but the moist environment (my boats lived in the water) really took its toll. A new carb was cheaper than the mechanic and always made the boat run better. Sometimes I had to do a tune up as well (including lubing the distributor weights) but there's not that much to go wrong in those older engines.

 

Only had one fuel pump failure - that pumped gas into the carb from a leaky diaphragm (use a marine fuel pump! Saved me there.). Replaced a few coils - never had that fix a problem.

 

One last possibility, check the water flow through the manifolds. If you get salt or hard water time, your cooling channels can get restricted. Localized overheating can cause poor running without the temp gauge showing it - especially under load. My manifolds don't last very long in my water before they are quite plugged.

 

Good luck,

Eric

[BraceMaker]

@eleeski that check valve should just thread out and let you pull the pick up tube up and out of the tank.

[So_I_Ski]

@eleeski I removed the entire assembly, fuel inlet hose, pickup tube and float all ran through a hard plastic plate about 6 x 4 inches. Screen at the end of the pickup tube was whistle clean. As for an in tank pickup filter, if there is one I couldn't see it on that assembly.

[eleeski]

@So_I_Ski Thanks. I was hoping you had a trick but it sounds like your tank was designed for easy removal. Things are improving from 1979.

 

I might check the pickup lines for cracks. Air might get in and cause the problems?

 

@BraceMaker Mine is definitely welded in place. To access it I will have to cut some sort of hole. I'm reluctant to cut the steel tank for fear of sparks blowing it up (I know someone who was killed that way). I'll probably fill the tank with water to cut the hole. Big pain. The outboard tanks are pretty easy so not much incentive to do the job.

 

Eric

[So_I_Ski]

AND THE WINNER IS ....... anybody that stuck with faulty fuel pump even though that was the second thing I replaced! I hot wired the fuel pump and it still failed although initially it looked like it was going to run. Turns out the extra voltage from hot wiring helped it run a little longer but eventually the pump got worse to the point where I couldn't even start the boat without reattaching the alligator clip I had coming from the pump directly to the battery. So what a painful process just because replacement parts (from China no doubt) are so unreliable. Thanks again to all the ballers that offered possible remedies.

[Keith_Menard]

@So_I_Ski I may not have won the Scotch (btw, there are some awesome Bourbons out there right now) but I am really happy you got it!

[LeonL]

So_you_fix. What pump did you use for the fix.

[So_I_Ski]

AAAARGGHH - installed the new pump and NO CHANGE! So it wasn't the freakin pump after all that. Hot wired the new pump again but this time removed both positive and negative leads first to eliminate any possibility of something back feeding like a murphy switch and when it still ran only at 2600 that indicated conclusively that the problem was somewhere between the pump and the tank. Removed the pickup assembly for the second time and no defects. Then just before I reinstalled that assembly someone suggested a possible fuel line kink or collapse so I followed that line but no obvious kink or soft spot.

 

Now, to get at the screws to remove the pickup I had to remove the eight inch section with the new fuel filter so just as I was about to put that back I decided to eliminate that possibility by plugging into the tank without that section. Just as I went to plug the line back in, I looked into the line and low and behold there was my blockage, big as life and twice as ugly. Cut one inch off the line and held it up to the sun where I was shocked to be looking at a thin orange film covering the hole in the line. Turns out that there is a lining in the fuel hose which had broken down over the years and as it folded over restricted the flow. Three weeks and five hundred later motor running great again and I own a spare fuel pump. I don't remember if anyone suggested that possibility but if so then I am kicking my ass for not looking there first. And @LeonL It was a Carter pump which I replaced with another Carter model 4601hp.

[eleeski]

Stoked that you solved the problem.

 

I'll have to check the American Skier tank for your issue but I still have to make that dangerous cut in the tank.

 

I was pretty close in my diagnosis. Not perfect so we can toast to the frustrations of mechaniching over some Jim Beam!

 

If it's not electrical it's fuel.

 

Unless there's oil filling the bilge - like the old MC. It's getting an electric motor for it - someday.

 

Eric

 

Edit. Figured out it wasn't the in tank line but the main line. I guess I owe you the Jim Beam.

[skiinxs]

Alcohol in fuel causes lots of problems. I have seen fuel lines swollen to three times their normal size. Even at 10%, you never really know if the alcohol has separated out in the tank you get your fuel from, could be anywhere from zero to 100%. This is very dangerous in boats, as a leaking fuel line could kill you and your passengers,

[eleeski]

Modern fuel lines tolerate ethanol just fine. If your fuel lines are old enough to be affected by ethanol, they should be replaced anyway. Rubber doesn't last forever and is a safety item that needs regular maintenance. 20 year old rubber fuel lines should be replaced. Then run the normal fuel ( with its ethanol) with no worries. Do ski enough to use your fuel before it goes bad.

 

Eric

[So_I_Ski]

@eleeski Thanks Eric for the advice. It was my intention to replace my fuel line at the end of this season in light of my experience and since my line is now 13 years old. And I certainly ski enough to ensure that my fuel never goes bad.