92 Excel 351W quits under load
Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Engine Repair
Forum Discription: Engine problems and solutions
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=48745
Printed Date: November-23-2024 at 1:51pm
Topic: 92 Excel 351W quits under load
Posted By: Brian0445
Subject: 92 Excel 351W quits under load
Date Posted: May-26-2020 at 11:48pm
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Hello New here to the forum! Looking for some advice or possible guidance. The problem I am expierencing is engine runs fine under no load (in neutral) at various RPM's. Once under load anything over 2400-2500 RPMS the engine will run fine with no hesitation, backfire, or issues for 10-15 seconds and then engine cuts out but if I back out of the throttle it will idle fine (most of the time) wait at idle speed or lower RPMS then retry again to have same thing happen. If I run at higher RPM it will run for a shorter period of time. I installed a new engine long block 351W in August of 2019. The engine has approx 20 hrs. End of last season the original Pro-Tec ignition failed and replaced with DUI marine 7000 Distributor and new wires, and plugs. After spring un-winterizing running on a hose and bucket at home everything engine ran fine, went to launch at lake and wouldn't start. Found broken rotor parts in distributor under cap. I removed broken pieces, and replaced the rotor didn't seem like anything else was damaged, boat started to not run under load. To rule out any fuel issues (I always run 91 non-ethanal and used marine fuel stabilizer in 2 tanks before winterization) I have replaced fuel filter, checked fuel shutoff, checked anti siphon valve at fuel tank, drained and refueled tank with fresh gas and additve, checked inlet screen at carburetor (which was a little plugged, and carburetor was "rebuilt" @ engine installation. Ive checked the mechanical fuel pump (produces 6psi and holds for over hour), replaced spark plugs and re-gapped new plugs to .55, checked the timing with timing light (28 deg @3000RPM).When I removed the plugs they were not fouled and were a tan brown color. Removed the Holley 4160 Primary and Secondary Float bowls and checked the jets in primary section, checked the float needle valve and everything seemed good. Adjusted the idle air mixture screws (turned in all the way and backed out 1.5 turns) It seems like its starving for fuel. When I removed the plugs they were not fouled and were a tan brown color. Not sure if I have a carburetor issue or a issue with mechanical fuel pump. Can a fuel pump show within spec pressure but not pump required fuel? I bench tested the fuel pump and checked for pressure as it was off the engine I replaced. It doesn't show any fuel in clear line going to spark arrestor on top of carburetor. Thanks for any input!! ------------- 92 Nautique Excel Open Bow 351W, DUI Distributor Conversion Wake Tower |
Replies:
Posted By: SNobsessed
Date Posted: May-27-2020 at 12:04am
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You might want to look for blockage in the exhaust system. It could be choking out. ------------- “Beer is proof that God loves us and wants us to be happy.” Ben Franklin |
Posted By: Jonny Quest
Date Posted: May-27-2020 at 1:42am
Please elaborate on what "holds for over hour" means. A fuel pump that is failing may be able to keep up at idle speed, but might struggle at higher RPM while under load. I'm assuming that your "long block" did not come with a fuel pump, correct? Is the mechanical fuel pump a Carter? You may want to do some additional fuel pump evaluation. JQ ------------- Current 2003 Ski Nautique 206 Limited Previous 2001 Ski Nautique Open Bow 1994 Ski Nautique Open Bow Aqua skiing, ergo sum |
Brian0445 wrote:Posted By: KENO
Date Posted: May-27-2020 at 8:23am
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You mentioned checking /cleaning lots of the fuel system but I didn't see any mention of the suction line inside the fuel tank. Usually there's a small screen type filter/strainer that's there to keep junk from getting to the antisiphon valve. You might look and find nothing installed there or maybe you'll find a screen blocked with junk restricting fuel flow, but you won't know till you look  Otherwise like JQ said, it could be the pump. You could hook up to a temporary tank that's vented so the pump won't draw a vacuum in the tank, and run the engine under load and see how it runs to rule out everything on the suction side of the pump. If you had the pressure gauge hooked up at the same time, you'll know what the pump is doing under loaded real life conditions Also since this started after distributor issues, You might consider that you have a distributor problem even if you think it's fuel Then again, how's the carburetor?.
Not really related but 28 degrees at 3000 rpm is a little on the conservative side for a DUI |
Posted By: Brian0445
Date Posted: May-27-2020 at 8:33am
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Thanks for the responses! I forgot to mention when I pumped out the fuel of the fuel tank I also removed the tank pickup tube and inlet screen was clean. I tested the fuel pump with a pressure/vac gauge. I installed it on the outlet port of the pump and cranked the engine and gauge read 6-6,5 psi. I left the gauge installed for over a hour and it held the 6-6.5 psi. ------------- 92 Nautique Excel Open Bow 351W, DUI Distributor Conversion Wake Tower |
Posted By: KENO
Date Posted: May-27-2020 at 8:44am
Well at least that's out of the way, but do the other checks or go and buy another fuel pump for "troubleshooting purposes". Carter M60389 for a wild variety of prices if you shop around and if it's not the pump, it's good to have a spare on hand
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Posted By: Brian0445
Date Posted: May-29-2020 at 4:44pm
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Update.... Ive since replaced the mechanical lift pump with the original Carter pump. Water tested and same issues. I tried running out of different fuel tank to eliminate any fuel issues in the system. Water tested again with same issues. Called DUI distributors explained my issues said it may be the coil or cap due to rotor issue. They are going to send out a replacement. Hopefully that will fix the issue. Felt like a fuel issue but I'm at whits end! Has anyone else experienced a failed cap/coil to run under load then quit, and rebound if you throttle back to idle? ------------- 92 Nautique Excel Open Bow 351W, DUI Distributor Conversion Wake Tower |
Posted By: KENO
Date Posted: May-29-2020 at 6:33pm
That's why this was mentioned before. You wouldn't be the first and certainly won't be the last to think it was one and have it be the other. Whichever it turns out to be at least you'll have a few fresh distributor parts installed
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Posted By: Hollywood
Date Posted: May-29-2020 at 8:25pm
| Surely wouldn’t hurt to triple check your firing order. How do the plugs look? |
Posted By: Canuck-Surfer
Date Posted: May-31-2020 at 1:26am
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Could the transmission be locking up under load and killing engine? This happened to me a few weeks ago. We spent the winter rebuilding the 351 GT 40 block. On first water test the boat ran fine and light loads up to about 2000 RPM as soon as you got up to about 2500 or 3000 RPM the transmission would lock up and immediately kill the engine. You turn it off and back on and you could put it in to gear fine and move until enough load got put on it and it would happen again. Once we pulled the transmission and opened it up the drum is completely separated from the splined shaft which is why everybody hates those original 40A transmissions. Brand new transmission is sitting in the garage ready to get installed. ------------- 1996 Sport Nautique GT40 EFI |
Posted By: Brian0445
Date Posted: June-01-2020 at 10:34am
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The transmission doesn't seem to lock up causing the engine to quit. The engine stumbles and if you back out of the throttle the engine will idle down and continue to run. I spoke with DUI they said they will be sending a new distributor cap and coil. They said it may be the problem. ------------- 92 Nautique Excel Open Bow 351W, DUI Distributor Conversion Wake Tower |
Posted By: Brian0445
Date Posted: June-06-2020 at 3:10pm
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Update: Fixed the issue. Had the carburetor last year when the new engine was installed, so I assumed the carburetor was all good. Im not a carburetor guy but watched a few youtube videos and purchased a rebuild kit. Took about a hour to completely rebuild. Found what looked liked leaves or some type of organic material in the float bowl needle valve assembly in both the main and secondary fuel bowls. Would have never expected it as the rest of the fuel system was cleaned last year when the engine was installed. I checked the inlet screen on the gas inlet of the carburetor and was clean when I first experienced issues so didn't investigate any further. The fuel flow was blocked didn't really know how it even ran. Water tested for about 2 hrs and seems to be fine at all RPM Ranges. Wanted to say thanks for all the advice and helpful tips!! ------------- 92 Nautique Excel Open Bow 351W, DUI Distributor Conversion Wake Tower |