90hp - 90ETLJ - Just not quite "perfect"

[JKTrevecca]

Thank you in advance for taking the time to read this. I'll do my best to be concise.


Purchased a 1986 90hp this week. Carbs were professionally rebuilt in 3/2014 by four corners marina in nashville. I have all paperwork. In addition to carb rebuild, the bulb and fuel lines were replaced. Prior owner paid about 500 bucks for this. When I first purchased the boat, it would start and run great for about 45 seconds at idle, then begin to miss on 1 cyl. I removed the "out" fuel line from the pump and attached a 4 foot hose. I then started the engine (had fuel in the carb bowls) and there was little to no fuel being pumped out of the fuel pump. I thought it had to be the fuel pump so I replaced it. Exact same thing with a new pump. Then I began to eliminate variables by swapping fuel tanks first - same issue. Then I took a known good fuel primer bulb and used it with a known good and clean portable tank. With that, the motor ran good continuosly so off to the river I went. In the water, the engine runs consistently but has what feels like an intermittent miss and tops out at 4200 RPM and 30mph on a 16 ft fiberglass v-hull run-about. (junk boat that the motor came with).


Compression is 115,115,110
Fuel pumps very well with the "good" bulb and tank (I tested it using method captioned above)


Since the "new" bulb went bad after only 3-4 months, is it possible or likely the carbs are dirty again too? The prior owner said he only used the boat 1 time since the carbs were rebuilt and was selling the boat to avoid forclosure on his house.

Is it reasonable for me to ask the marina that re-built the carbs to check and warranty their work or is 3-4 months too long to expect them to look at it again without charging me?

Any other advice? I can post pix and a video later if that helps. It runs consistent but my 70hp Evinrude on a 16ft aluminum deep v has more power and certainly higher RPMS and top speed. I bought the new boat with intentions of using the 90hp yamaha on my fishing boat but if I can't get it to run any better than this, I'll just flip and sell the entire rig as-is and keep my 70hp and be happy.

Thanks again. I appreciate your time and sharing of knowledge!

-- Jason

 

[99yam40]

if you pump trash into cleaned carbs you get to clean them again.
Why would anyone redo the carbs for free , if it was not their work that was at fault

 

[JKTrevecca]

You bring up a good point that I completely understand and agree with 99yam40. I guess i'm having trouble wrapping my brain around the possibility that the carbs would need to be cleaned again after 3-4 months when a lawnmower or pressure-washer with a briggs engine can sit in my shed for a year and start up immediately with no carb rebuild/clean needed. However, if the carbs on these outboards are more picky and need to be cleaned b/c of trash, I wouldn't expect the shop to do it for free. I picked up the manuals from the public library today and will be more scientific and objective in pinpointing what's going on. Thanks for the help.

 

[99yam40]

If the tank, line, bulb, or pump has any trash in it where do you think it will go to when you fire up a motor that had cleaned carbs on it?
not hard to wrap your mind around that concept.
clean the carbs , pump the bulb and you get to clean the carbs again if there is any trash in any of the stuff before the carbs

 

[nayborbob2]

I would take off carbs and look in float bowl. That will tell you if there is a fouling problem. If you are not comfortable doing that yourself it will cost you. I just bought a 1986 70hp Yamaha and it was only running on 1 of 3 cylinders at idle. After taking off carbs I was not sure how it ran on the one! The carbs on my 70 are pretty simple. I would think yours might be also.

 

[JKTrevecca]

Thanks nayborbob2! I appreciate the helpful post/reply. I'm glad you got your 70hp running better.

Since I posted, I removed and cleaned my carbs and now it runs perfect. I obtained 5200 RPM smooth as silk and about 40 MPH in a heavy and junky fiberglass boat that came with the motor. I'm hoping to get all the kinks worked out and move this motor to my aluminum fishing boat that currently has a 70hp evinrude on it. Now the new "kink" that needs to be worked out.... After running at WOT for about 45 seconds, the buzzer/warning goes off and the RPMS drop to 2k. The oil tank is full but both the "full" oil light and the "empty" or red oil light are on when the buzzer sounds. If I cycle the key off/on a couple times it goes off and then comes back on again as soon as I accelerate. I didn't push my luck running it in case it truly isn't getting enough oil. I know it's getting at least some oil based on the exhaust smoke being slightly blue.

From what I'm reading, the warning buzzer + the green and red lights on indicate an oil delivery problem. Correct? Can anyone with more experience share what exactly the system is sensing and where is it getting it's data/reading from? I read that to test the oil delivery system, I need to remove each oil line from the oil pump, run the engine at 1500 rpm for 3 minutes (on pre-mixed gas) and measure the oil output on each of the 3 oil injection hoses (installed in place of the hose that was removed) to see if the oil pump is working like it is supposed to for all 3 cyls. I may also remove the oil level sending unit, which I believe has a filter in it ????, and clean that filter in case it's causing a blockage. The prior owner of the boat told me he replaced the oil pump about a year ago but who knows. The entire engine on this thing looks un-touched and very clean.

Anybody have any other suggestions? Ideas? Experience with this symptom? The darn thing runs awesome until the light and buzzer come on and then it's being electronically limited.

Here is a picture of my tach. It has 3 oil indicator lights at the bottom. The right "oil tank full/green" light is on all the time b/c the oil tank is full I suppose. When the buzzer goes off, the left-most "oil tank empty/red" light comes on in addition to the green one.

Thank You! I know I have several posts going on here. I'd be happy to delete the other two if needed.

 

[JKTrevecca]

99yam40 - I appreciate the blunt feedback. It made me angry at you to begin with but after re-building the carbs, I have learned they can get gummed up in only 3 months.

 

[99yam40]

99yam40 - I appreciate the blunt feedback. It made me angry at you to begin with but after re-building the carbs, I have learned they can get gummed up in only 3 months.

Sometimes it will happen the same day you clean the carbs if you do not clean the stuff out of all the other places.

On the oil alarm,
not sure on a motor that old as to what all the lights mean.
Does this 90 have a motor mounted oil tank and a remote mounted one in the hull that pumps oil?

 

[nayborbob2]

I Bet you have a sensor problem. I have heard those oil pumps are pretty reliable...but no personal experience

 

[JKTrevecca]

Well dang it. I just broke an air-bleed screw on the oil pump. I read that after the oil tank has been disconnected (which it was for the carb removal), I'm supposed to bleed the oil injection system of air. Thinking that may have caused the alarm, I jumped all over it. When I did this, I over-tightened the bleed screw and broke it. I was able to get it all the way out but finding another one may prove difficult. It's a brass screw with a hole through the middle of it and another hold drilled cross-ways just below the head of the screw. It appears to be about 5-6mm metric threads.

Anyway. 99yam40 - This engine has only 1 oil tank and it is engine mounted. The oil pump is gravity fed from the bottom of the tank, then pumps the oil back up directly into the intake behind the carbs.

 

[99yam40]

good luck finding that screw.

There is no oil flow alarm,
only oil level so need to start checking the level switch and wiring to see what is going on

 

[JKTrevecca]

This alarm is driving me nuts! I was able to make a replacement bleeder screw using a M5 x 0.80 machine screw and drilling a 1/16inch hole in it cross ways just below the head and then another 1/16inch hole through the bottom of the screw up to where I drilled cross ways. Worked like a charm and cost me $0.23.

However, the alarm is CRAZY. I removed, cleaned, and tested the oil level sending unit. Works as it should. I removed the t-stat and while I had the cover off, ran the engine on muffs to make sure it was pumping water all the way to the top and it was, in abundance. Water went everywhere. I mixed some oil and gas in a portable tank just to be safe and went to the lake. I unplugged the oil sending unit wiring to eliminate that variable. Alarm still went off after about 1-2 minutes at WOT. However, the red "oil" light didn't come on this time (perhaps b/c that wire was disconnected). I Removed cowling and touched head. It was very warm but not scalding hot. Normal? Tell-tale is/was slightly warm but kind of like bath water. Definitely not "HOT" to the touch.

I noticed when running the engine on muffs with the t-stat cover removed, the water comes out of the tell-tale before it gets to the top of the head. This tells me the tell tail is at the beginning of the cooling circuit and not the end. So... Could I have a severe water-flow restriction somewhere behind the tell-tale and behind/below the t-stat cover? If an engine is overheating, would I still be able to touch the head w/o burning my hand? What is "normal" temp for the exterior of the cyl head on these things?

I'm going to remove the temp sending unit and test it in a pot of water to see what temp is when it closes it's circuit.

Thanks for listening and thinking with me on this!