Bogging problem Evinrude crossflow

[sparkroost]

Hi all. I have been trying to figure out a what seems to be a fuel problem. This is an evinrude '73 V4 crossflow. I can get on plane, but after a few moments the engine dies down, as it's in need of fuel. Squeezing the primer bulb does nothing. Depressing the choke primer helps a little but won't drown out the motor. As if there is no fuel there but enough to make it run a little better. I vacuum tested the lines. Tried an aux spare tank. Swapped carbs. Checked pulse line to fuel pump. checked fuel pump diaphram for cuts and tears. Pump is 1 year old. Primer bulb get's hard and does not pump anymore once pumped. Engine never stalls, just bogs down and I have to reduce the throttle to idle, wait a few moments, then I can get on plane again.<br /><br />At first it was surging(a few weeks back) It wouldn't take 5400rpm, starting to bog and rev up. Had to back down to 4000 to run fine. Now I can get up to 5k, but for a short period, then it's like it's out of gas.. but never stalls.<br /><br />Idles like a dream and has great power. EGT's seem like they drop when this occurs, but not much. Don't smell raw fuel. Carbs are not spitting.<br /><br />Would bad gas do this? It's the only thing I can think of I didn't try.<br /><br />Please help<br /><br />Spark

 

[walleyehed]

Re: Bogging problem Evinrude crossflow

Ignition???? How do the plugs look....tan, black, white???? If you think it may be fuel starvation, it SHOULD show up when you look at the plugs if it hasn't idled very long. Kill it when it's acting up, and take a peak...????

 

[walleyehed]

Re: Bogging problem Evinrude crossflow

BTW, you can run lean of peak EGT, and get lower temps .........

 

[Hooty]

Re: Bogging problem Evinrude crossflow

When it's fallin' on it's face, try the ole "premix-in-a-spraybottle" trick and see if that breaths life into it. Unless it's been changed, you've got real choke butterflies in those carburetors instead of a primer so choking should either cause it to perk up or choke down. If it doesn't choke down, there's no fuel there.<br /><br />c/6<br />Hooty

 

[sparkroost]

Re: Bogging problem Evinrude crossflow

I converted it to electric primer. In the past, running at WOT, the primer would drown out the motor in a matter of seconds. This is not happening now. It improves it, but not cure it, and definatly does not drown it out. That makes me think there is no fuel after the fuel pump. If this were true, I should be able to squeeze primer bulb and help things. No so. I can't create a load at the house, so I have to take it out and try the spray bottle thing. What if it is getting fuel? What could it be from that standpoint? I have excellent compression, idles perfectly. All gauges are working and within normal operation levels.<br /><br />On the plugs, I will have to check that next time out.<br /><br />Walley, ignition??? What does that mean? Could I have an ignition problem? Never crossed my mind. <br /><br />On the way back in tonight I gave just enough throttle that it would not get on plane. I think it was at 3000 rpm. The boat wanted to plane. but was just shy of doing it. The boat ran good like this for a good 100 yards, then.. I could tell if I floored it it would fall on it's face.. so I tried and sure enough... backed off for a minute and gunned it,power again. Then shortly after bogg.<br /><br />I had the fuel pump discharge line off and squeezed the bulb, plenty of fuel coming out pump. I can only imagine when I squeeze the bulb it's keeping the float bowls full.<br /><br />Is it possible that the ignition is saturated at higher rpm's due to a powerpack issue? I wouldn't have considered this from my symptoms but wierder things have happened. I have never heard a backfire or noticed anything along those lines. <br /><br />The engine does sound a little funny when this happens. Almost like it's misfiring or a couple cylinders are dry. Clears up within a few moments.<br /><br />The problem is..I can't work on a problem at home that I can't see! I will try and get a test wheel tomorrow so I can combat this problem at home.<br /><br />If I had bad fuel, wouldn't I have a problem at idle as well?<br /><br />BTW, This motor has about 75-100 gallons through her since rebuild. Running great, no problems. I did have the problem after a new re-fill. NOthing abnormal happened that I can account for this problem.<br /><br />Compression is 150*4, water pressure 25psi, egt 1100WOT, 500 idle, tach works, charging system fine, penzoil syn/blend w/89 octane and lead added to fuel @ 40:1. ql77jc4 plugs. boysen reeds(looked at reeds when I swapped carbs, none missing or broken). no signs of shavings on plugs. If I rotate engine flywheel, holds compression on all 4 cyls, bleeding off the same amount very slowly.<br /><br />If I lost pulses to fuel pump, wouldn't pumping the bulb bypass the pump?<br /><br />Could a faulty powerpack do this??<br /><br />Sorry for the long winded story. <br /><br />Stumped

 

[ob]

Re: Bogging problem Evinrude crossflow

That makes me think there is no fuel after the fuel pump. If this were true, I should be able to squeeze primer bulb and help things.<br /><br />If you have a restriction in your midrange or high speed orifices/porting,or bowl pickup tubes,sqeeezing the fuel primer bulb will not help.

 

[sparkroost]

Re: Bogging problem Evinrude crossflow

I tried 2 set's of carbs. 1 set has only 4 jets pr. carb, the main and the primary x2. The 2nd set has 7 pr. carb.. Both carbs did exactly the same thing. Fuel is filtered and visible in a sight glass.<br /><br />More I think about it.. it's gotta be fuel. Before it would probally kill the engine if I held the choke primer long enough. Now I can hold in indefinatly when this bogg occurs. If I hit the primer when idling it will kill the enigne in about 5 seconds. If I had a restriction in the jetting, the choke would bypass that. The choke primer(s) are connected at the base of the carb going to the center channel of the intake.

 

[Hooty]

Re: Bogging problem Evinrude crossflow

Bingo!<br /><br />c/6<br />Hooty

 

[walleyehed]

Re: Bogging problem Evinrude crossflow

I'd still be looking at the plugs when it acts up and see what you have before you burn it down looking for something else.<br /> pumping the bulb puts way more pressure on the floats than the fuel pump could ever do....If pumping the bulb does nothing, you have one hell of a restriction, and you WILL melt it.<br /> I would also look, or consider the fuel lines having what is known as a "flaper" inside-the inner fuel line coming apart, and blocking flow, which I could see being possible, but most likely not because pumping the bulb should create high pressure, and the bulb would feel squishy.<br /> Hooty is very possibly right, but I think you have other problems........my opinion....

 

[walleyehed]

Re: Bogging problem Evinrude crossflow

I'd still be looking at the plugs when it acts up and see what you have before you burn it down looking for something else.<br /> pumping the bulb puts way more pressure on the floats than the fuel pump could ever do....If pumping the bulb does nothing, you have one hell of a restriction, and you WILL melt it.<br /> I would also look, or consider the fuel lines having what is known as a "flaper" inside-the inner fuel line coming apart, and blocking flow, which I could see being possible, but most likely not because pumping the bulb should create high pressure, and the bulb would feel squishy.<br /> Hooty is very possibly right, but I think you have other problems........my opinion....

 

[sparkroost]

Re: Bogging problem Evinrude crossflow

welp... I figured it out. Really surprised at the outcome. When I bought gas, I had filled up my 22 gallon tank on board and another 10 gallon tank. I had anticipated going 100 miles that day and didn't get to go but 64. All of the 64 miles was low speed and some short jaunts. I do believe this starting acting up on that fill. When I had swapped tanks to the 10 gallon in testing I didn't really think about me filling that tank up the same time.<br /><br />I went through alot of testing before buying new gas. Thought I would have idle problems, never did.<br /><br />I emptied the 10 gallon tank today, put fresh in and ran it. I also swapped power pack and left air box cover off so I could squirt pre-mix in if need be.<br /><br />With the airbox cover off I gained another 600rpm. How can this be! this was with the cowling on.(the front cover is a the late style)<br /><br />Just to rule out the powerpack, I swapped to the on-board tank... sure enough bogged after a short burst of WOT.<br /><br />The reason that my primer was not drowning out the engine is because the fittings I used for the primer circuit were too small in diameter.<br /><br />Is it normal to get bad gas and have these symptoms?

 

[walleyehed]

Re: Bogging problem Evinrude crossflow

Are you saying it runs fine now????<br />My next question is, if it's still not running good, have you ran it without the cowl on????

 

[sparkroost]

Re: Bogging problem Evinrude crossflow

Running perfect. with the cowl on and the airbox cover off. Increased RPM 600. Can't understand that one. Everything under that cowl down to the foot was re-done by me, down to the bare metal. Everything was replaced aside from major parts. The airbox "side ports" were free from objects. I did a plug shop at 6500RPM. EGT said 1200-1250. Plugs were all tan. No dry powder. I found out another thing.. when running at 155-160 psi, pump gas doesn't do it. I had to back the timing down today 2 deg with 94 fuel. Unless that gas was not fresh. I usually add some lead at run it at 26deg. I can hear it if it pings. Well today It needed 2 less deg cause I didn't add the lead <br /><br />I swapped fuel supply lines today twice to verify test. Both times the engine bogged with the on board tank. And when I was troublshooting yesterday I used both tanks as well, but both were full of the same fuel and both bogged.<br /><br />Word of warning! It can happen, cause it did to me.

 

[walleyehed]

Re: Bogging problem Evinrude crossflow

Well, I'm happy you found your problem. I wasn't aware you had high comp heads. Have you ever tried a mix of high oct. pump gas with 100LL aviation gas????? I run about 25% 100LL. Nice thing about the 100 is it doesn't varnish, and acts as a stabilizer. I've tried it straight, but it's charactoristics just aren't right for running straight.<br /> Glad you found your problems!! Happy boating.