I thought I had all this figured out. I was having problems with the engine bogging bad in the last 1/3 of the throttle. Then sometimes it would start backfiring at over 2500 RPMs and not want to go over 3K RPM.
I did a tune up on the dist, replaced the IGN coil, took the air horn off the carb and set the floats, pumped all the fuel out of the tank, cleaned the tank, replaced the fuel tank vent hose, took the fuel tank pick up out and checked all connections, replaced fuel line from tank to fuel/water sep filter, and checked all spark plugs for proper gap.
The boat ran great after that. It ran perfect for about 15 hours of use. No bogging, no intermittent backfiring and not gong over 3K RPM.
So yesterday I went out for a couple hours and I noticed it was not running right. It would run fine up to 3500 RPM then start to bogg but it was different than the secondaries bog. When I got back to the dock I started checking things over and hooked up the timing light. The timing had moved from 8 to 2 so I checked the dwell and it had moved also. I replaced the points screw in the dist and set the gap, dwell, and timing again.
I went out today and there is about a 15 min no wake zone from where my dock is to the channel. I idled out to the channel and opened her up. Ran great, no bogging, secondaries opened up and it ran great. About 5 mins after that a small sailboat was coming by so I slowed down and moved some gear around. Then when I got back up on plane again the engine was bogging over 3500 RPM. I slowed to idle checked the dwell and timing and they were both good.
I drove around for a little while at about 3K RPM and tried going over but it would bogg every time. Then about an hours later it started right at about 3K RPM it would surge or hesitate, like I was keeping the throttle still but it the rpm would go up a little then down then up then down, if I gave it a good bit more gas it would die way down.
So Im thinking the fuel system. I hooked up a fuel pressure gauge where fuel enters the carb and it reads 3.5 PSI all the way from idle to WOT. The Edelbrock manual says to have 4-5 PSI min at WOT. I hooked a vacuum gauge up BEFORE the fuel water sep. Never not a bit of vacuum on it.
But here is what it looked like in the tube. You can see there is barely any fuel coming out of the hose from the tank.
http://www.youtube.com/watch?v=g3iQdprs5mI&feature=youtube_gdata
So then I hooked it up between the fuel water sep and the fuel pump.
I NEVER got any vacuum reading on it. There was however no air bubbles and the clear tube was full of fuel unlike the previous test above. Then I did the test where you pinch the line.
It never gets over 5 Hg vacuum and it take almost 60 seconds to get there.
http://www.youtube.com/watch?v=Y3VAa8Zi2a8&feature=youtube_gdata
The Capt Jasons rule about this is not clear in the thread. It says what outboards and sterndrives with mech fuel pumps should reach so much vacuum in 10 secs or the pump is supect.
But what about sterndrives with electric fuel pumps?
The pump on there came with the new engine a couple months ago. Its a Carter. All I could find on it was a number stamped in it. 40700E20A
Cant find one with this model number online but I did find a P-4070 which looks just like it. But all of these pumps they say are way better at pushing fuel then pulling it. I have about 3-4 ft of hose between the pump and the tank. And a fuel water sep filter.
You can see in the pics that the paint is coming off of it. I don't know if they painted it while the engine was being painted or if its the original that peeling off cause it got wet. The ones I found P-4070 are black also.
So what do you guys think? Fuel pump not up to par? Do I need one that is better at pulling fuel? But then again I was creating the kink in the hose less than 1 ft away from the pump.
What is the rule of thumb about the pump creating suction? It took me 60 seconds to get 5 Hg.
Can a fuel pump problem like this be comething that happens somtimes and not all the time? Boat was running great for about 15 hours since I changed the points and cleaned the fuel system.
Oh yea and I checked the fuel water sep and there was 0 water in it. Just wanted to make sure.
Thanks so much guys.
I did a tune up on the dist, replaced the IGN coil, took the air horn off the carb and set the floats, pumped all the fuel out of the tank, cleaned the tank, replaced the fuel tank vent hose, took the fuel tank pick up out and checked all connections, replaced fuel line from tank to fuel/water sep filter, and checked all spark plugs for proper gap.
The boat ran great after that. It ran perfect for about 15 hours of use. No bogging, no intermittent backfiring and not gong over 3K RPM.
So yesterday I went out for a couple hours and I noticed it was not running right. It would run fine up to 3500 RPM then start to bogg but it was different than the secondaries bog. When I got back to the dock I started checking things over and hooked up the timing light. The timing had moved from 8 to 2 so I checked the dwell and it had moved also. I replaced the points screw in the dist and set the gap, dwell, and timing again.
I went out today and there is about a 15 min no wake zone from where my dock is to the channel. I idled out to the channel and opened her up. Ran great, no bogging, secondaries opened up and it ran great. About 5 mins after that a small sailboat was coming by so I slowed down and moved some gear around. Then when I got back up on plane again the engine was bogging over 3500 RPM. I slowed to idle checked the dwell and timing and they were both good.
I drove around for a little while at about 3K RPM and tried going over but it would bogg every time. Then about an hours later it started right at about 3K RPM it would surge or hesitate, like I was keeping the throttle still but it the rpm would go up a little then down then up then down, if I gave it a good bit more gas it would die way down.
So Im thinking the fuel system. I hooked up a fuel pressure gauge where fuel enters the carb and it reads 3.5 PSI all the way from idle to WOT. The Edelbrock manual says to have 4-5 PSI min at WOT. I hooked a vacuum gauge up BEFORE the fuel water sep. Never not a bit of vacuum on it.
But here is what it looked like in the tube. You can see there is barely any fuel coming out of the hose from the tank.
http://www.youtube.com/watch?v=g3iQdprs5mI&feature=youtube_gdata
So then I hooked it up between the fuel water sep and the fuel pump.
I NEVER got any vacuum reading on it. There was however no air bubbles and the clear tube was full of fuel unlike the previous test above. Then I did the test where you pinch the line.
It never gets over 5 Hg vacuum and it take almost 60 seconds to get there.
http://www.youtube.com/watch?v=Y3VAa8Zi2a8&feature=youtube_gdata
The Capt Jasons rule about this is not clear in the thread. It says what outboards and sterndrives with mech fuel pumps should reach so much vacuum in 10 secs or the pump is supect.
But what about sterndrives with electric fuel pumps?
The pump on there came with the new engine a couple months ago. Its a Carter. All I could find on it was a number stamped in it. 40700E20A
Cant find one with this model number online but I did find a P-4070 which looks just like it. But all of these pumps they say are way better at pushing fuel then pulling it. I have about 3-4 ft of hose between the pump and the tank. And a fuel water sep filter.
You can see in the pics that the paint is coming off of it. I don't know if they painted it while the engine was being painted or if its the original that peeling off cause it got wet. The ones I found P-4070 are black also.
So what do you guys think? Fuel pump not up to par? Do I need one that is better at pulling fuel? But then again I was creating the kink in the hose less than 1 ft away from the pump.
What is the rule of thumb about the pump creating suction? It took me 60 seconds to get 5 Hg.
Can a fuel pump problem like this be comething that happens somtimes and not all the time? Boat was running great for about 15 hours since I changed the points and cleaned the fuel system.
Oh yea and I checked the fuel water sep and there was 0 water in it. Just wanted to make sure.
Thanks so much guys.
