Runs great on hose, Dies under load

[Just-in Time]

Hello all, my '94 90hp evinrude O/B seems to run great on land but in water dies anything above idle when in gear. Same for forward or reverse. Seems to run marginally better with the tilt way up. Engine is recently purchased and i've done a fair amount of repairs already. these include cleaning the carbs, replacing fuel lines, inspecting and cleaning fuel pump, replacing water pump, replacing head gaskets and deflectors, replacing thermostats, & other repairs not important to this issue.
I noticed the problem last night. she rode fine for a few hours, turned it on and off several times with no issues, then all of a sudden, after sitting for only a few minutes, it would only idle. had to idle miles back to the boat launch.
I'm more or less mechanically inclined and am open to trying most things. I appreciate your responses in advance. thanks a bunch, justin

 

[Daviet]

Re: Runs great on hose, Dies under load

Couple of basic checks, compression and spark, easy to check and to elimatate those out of the picture.
It sounds like you still have a fuel problem, when you cleaned your carbs did you remove all of the jets and clean all of the orifices and install new carb kits? Are the float levels correct,"runs better tilted up"?

 

[mrcj001]

Re: Runs great on hose, Dies under load

Sounds like a ignition issue. Once engine is warm, some ignition parts start to fail.

Do a spark drop test once the engine is warm and see if there is a cylinder not getting good spark.

Usually, when the engine wont go under load, there is a cylinder(s) dropping.

 

[Just-in Time]

Re: Runs great on hose, Dies under load

Couple of basic checks, compression and spark, easy to check and to elimatate those out of the picture.
It sounds like you still have a fuel problem, when you cleaned your carbs did you remove all of the jets and clean all of the orifices and install new carb kits? Are the float levels correct,"runs better tilted up"?

I checked the compression before the issue and it was fine but i'll check it again. i did clean the jets but wasn't exactly sure how to adjust the float levels. Is it possible for the floats to go from being correct for hours to suddenly being off so far the engine would only idle? Also it appears the previous owner recently did a carb rebuild as all the components look very new.
I thought perhaps the running better more tilted up was because it was putting less of a load on the engine.
thanks for the quick reply. I'll check compression and spark

 

[Just-in Time]

Re: Runs great on hose, Dies under load

Sounds like a ignition issue. Once engine is warm, some ignition parts start to fail.

Do a spark drop test once the engine is warm and see if there is a cylinder not getting good spark.

Usually, when the engine wont go under load, there is a cylinder(s) dropping.

Ok thanks, can i do that on the hose or does it need to be in water/tank?
thanks for the quick reply

 

[jtexas]

Re: Runs great on hose, Dies under load

See a lot of posts with newly acquired motors running great awhile then crapping out. Usually turns out to be fuel related -- my thought is, some crap built up in the tank, or the lines, or somewhere along the way gets dislodged, or dissolved by the ethanol in the gas, and delivered into the carbs, but that's just a theory.

Got fresh fuel? Tank clear of water/debris? Fuel line holding pressure? Tank vent open and clear?

Float adjustment: hold the carb body upside down, the float should hang parallel with the carb body. A float could suddenly start sticking shut, starving the cylinders it feeds. Or sticking open, flooding 'em. Can't say how probable it is, but it happens. I like your engine-load-tilt theory better, but if you aren't sure you got 'em right the first time, I'd just go ahead & reset 'em.

Use an inline spark tester clipped to the engine block, gap set at 7/16" for your spark test. If it can't jump a 1/2" gap in open air without a spark plug, it won't fire in the hole under heat and compression. Test it on the muffs is fine.

 

[R1racer]

Re: Runs great on hose, Dies under load

Am working on My friend 70HP 1986 Evinrude that do the same exact thing ,Great idle shift fwd and reverse on the hose, Take it to the water and she is a different Eng .

I did read your post yesterday, I noticed when i tilted this 70hp up where the lower unit just in the water it run , shift both direction like a dream . The carbs been done and went twice over the float & the jet setting which they are fixed by the way so no adjustment needed... The old fashion spark test show good spark ...

Compression suppose to be ok . I could swear on 2 things it either droops a cylinder when it gets warm or i noticed the top carb got fuel dripping out the throat but not way much but noticeable and this drips they looked like lightly milky in a way ... Left me to wonder there might be some water intrusion to the 6gal fuel tank. However the main issue that it dies under a load unless i slam it to full throttle ... Don?t mean to high jack Your thread but i figured to share as am experiencing the same issue

 

[putawaywet]

Re: Runs great on hose, Dies under load

Im having the exact problem with my 93' 115.
I did get on plane by standing on the choke.
Idle speed runs fantastic with no choke.
Planed out runs great only with full choke.
New fuel, oil, plugs and cleaned all the contacts.
Im thinking deposits in the fuel system/carbs..
Its been sitting for two years.

 

[R1racer]

Re: Runs great on hose, Dies under load

I believe if you do a good carb Cleaning or rebuilt kit ..Fresh fuel filter along with overall check on your fuel line ,Spark tune up you will be golden ....Specially if she run on full choke wide open ...Good luck

 

[price chris craft]

Re: Runs great on hose, Dies under load

Please click one of the Quick Reply icons in the posts above to activate Quick Reply.

 

[price chris craft]

Re: Runs great on hose, Dies under load

Same issue on my i/o float was sticking and linkage three cleanings of carb before it ran right. Also could be built up crap in engine and fuel lines

 

[jtexas]

Re: Runs great on hose, Dies under load

more than one motor per thread is confusing.

R1racer and putawaywet please start your own threads.

 

[Just-in Time]

Re: Runs great on hose, Dies under load

alright guys, I took the boat out to diagnose the problem when in the water and for awhile i couldnt get it to have that issue again. eventually though, it did exactly what i described before: would only idle in reverse or drive and dies when given throttle. however, i did get a piece of good information. we learned that if someone pumps the fuel just until we're on a plane, the boat will run fine. we had to do this several times and it worked every time.

on a side note, that was the boat ride from hell, ran aground at full speed and got thrown to the front of the boat, couldnt start the engine for hours after that then ran out of gas 1/2 mile from the ramp.

Im planning on checking the gearcase oil for water intrusion because im thinking its likely the propseal broke. is there anything else i should check after running aground?
thanks guys

 

[jtexas]

Re: Runs great on hose, Dies under load

Sounds like insufficient vacuum at low RPMs. Check the pulse line to the fuel pump. You might end up rebuilding the pump.

If it sucked in a load of sand, the water pump might be compromised.

 

[Just-in Time]

Re: Runs great on hose, Dies under load

Sounds like insufficient vacuum at low RPMs. Check the pulse line to the fuel pump. You might end up rebuilding the pump.

The hose seems to be in good shape but ill put the air compressor on it tonight to check for leaks. I took apart the fuel pump and it looks brand new. Would i be able to see some form of malfunction?

If it sucked in a load of sand, the water pump might be compromised.

Okay, so should i check the impeller for any signs of damage or should i be concerned about the gaskets being broke?
there was an incredible amount of sand. The sky above my boat darkened for the moments while sand rained from the air. I had no idea that much sand could be thrust into the air that quickly.
thanks for the help

 

[jtexas]

Re: Runs great on hose, Dies under load

The hull hit a sand bar, or just the lower unit? I guess there are worse things you could run into. Any ideas why it wouldn't restart?

I never heard of propshaft seals being damaged by impact, but I wouldn't discourage you from checking the oil for water.

Sand in the water pump could score the pressure plate and/or that chrome housing insert, is what I'd look for. Maybe the impeller. That would diminish the effectiveness and maybe shorten the useful life of the impeller.

I can't say for sure if a new diaphram would solve your problem, since it runs fine at high speed. I doubt any problems would be evident. Is that the VRO pump?

 

[jmendoza]

Re: Runs great on hose, Dies under load

Check the o ring on the fuel line connector, and the clamps on the fuel lines. Any slight leakage will sometimes cause the pump to cavitate and not deliver enought fuel for full throttle. Make sure the tank is venting too. If you ran in sand for a while, I would be worried about the pump, but if it stalled when you hit the sand bar, you are probably OK. Check the prop hub rubber bushing and be sure it did not tear or slip, as it it supposed to sacrafice itself when you have a blade strike. If the lower unit/gearcase oil is milky, it's usually becuase you did not use new nylon seals when putting the fill and drain screws in, and they need to be quite tight, or, you have bad shaft seals. Rinse out the milky oil (if it is milky) with 50:1 gas oil mix.

 

[jtexas]

Re: Runs great on hose, Dies under load

... Rinse out the milky oil (if it is milky) with 50:1 gas oil mix.

I don't think putting gasoline in the lower unit is a good idea. just drain & refill with fresh gear oil will be fine.

if you do find water, there's plenty iboats threads about ways of pinpointing the source, so no need to jump to conclusions.

 

[Just-in Time]

Re: Runs great on hose, Dies under load

The hull hit a sand bar, or just the lower unit? I guess there are worse things you could run into. Any ideas why it wouldn't restart?

I never heard of propshaft seals being damaged by impact, but I wouldn't discourage you from checking the oil for water.

Sand in the water pump could score the pressure plate and/or that chrome housing insert, is what I'd look for. Maybe the impeller. That would diminish the effectiveness and maybe shorten the useful life of the impeller.

I can't say for sure if a new diaphram would solve your problem, since it runs fine at high speed. I doubt any problems would be evident. Is that the VRO pump?

the hull hit the sand bar a little but it was about 10 inches deep and i was on a plane so pretty much just the lower unit. the engine lifted up almost all the way. instead of saying the engine wouldnt start i should have said it had a very difficult time starting. it would kind of run intermittently. on and off for awhile. (mostly off)

I'll planning on dropping the lower unit this weekend and checking the water pump. hopefully its fine because i just rebuilt it.

I believe my model engine does have a vro but the previous owner removed it and now i premix.

 

[Just-in Time]

Re: Runs great on hose, Dies under load

Check the o ring on the fuel line connector, and the clamps on the fuel lines. Any slight leakage will sometimes cause the pump to cavitate and not deliver enought fuel for full throttle. Make sure the tank is venting too. If you ran in sand for a while, I would be worried about the pump, but if it stalled when you hit the sand bar, you are probably OK. Check the prop hub rubber bushing and be sure it did not tear or slip, as it it supposed to sacrafice itself when you have a blade strike. If the lower unit/gearcase oil is milky, it's usually becuase you did not use new nylon seals when putting the fill and drain screws in, and they need to be quite tight, or, you have bad shaft seals. Rinse out the milky oil (if it is milky) with 50:1 gas oil mix.

I put a new connector on the fuel line (the one that goes from the line to the engine) recently so it should be fine. fits very snug. Im thinking ill hook up the air compressor to the fuel line and listen for leaks.
To me however, since the problem happens intermittently it seems unlikely to be a break in a fuel hose. It seems like that would cause the problem to happen constantly. Seems most likely a problem with the fuel pump but it looks fine visually. i dont know of any way to test the fuel pump
thanks very much for the reply