Perplexing speed drop problem 90 hp 2 stroke

[RonKMiller]

My 1987 ETLH 90 is exhibiting a speed drop issue and reverting to "safe mode"... yet the buzzer alarm is not sounding at the same time.

A couple of questions:

1. I checked the thermoswitch with the hot water dip continuity check, it was almost spot on so - that eliminates a bad sensor there. I heated the thermoswitch with a heat gun on low power while connected and it DID trigger the buzzer - as expected.

2. My oil reservoir is half way full and displays a green light, but is it possible the breather (I see they changed the design and eliminated this after 1988 in favor of a different design) on top of the reservoir is plugged and creating a vacuum and restricting flow, thereby triggering the speed drop function? The speed drop function is only supposed to happen when it has less than 0.4 qts in the reservoir, and the alarm is supposed to sound along with the red light displayed on the tach.

3. I recently rebuilt the impeller and have an impressive pee stream at idle but no psi reading. The display shows 5psi when I throttle up to about 2000 rpm but does not climb above that. Should I see a higher and higher psi on the gauge as the engine revs up? IF so I may need to revisit the impeller rebuild even though I feel I did it correctly - or perhaps the connecting water tube is not transporting all the water that it can into the head...

4. Do the buzzer and speed drop always go hand in hand - or is it possible to get one without the other?

Dang, I'm really stumped on this one. Any direction here would be greatly appreciated.

Other than that, the motor runs great!

Picture of my "trailer on a toon" attached for your viewing enjoyment. It was named the "Y knot?"

[200090tlry]

This is my last post for awhile there is plenty to read up on

Fuel related? Starts with FP

[99yam40]

Yes alarm and RPM reduction should happen at the same time

You can check to see if it is going into RPM reduction by watching the timing as that is how the RPM reduction is con*****ed I believe on that motor

[RonKMiller]

Ah, thanks guys...

Both good thoughts.

Fuel pressure could indeed be the culprit, but I've got all new hoses, tanks, fuel/water seperator and a new fuel pump. I did bypass the engine mounted filter since I thought it was overkill. The only thing I did not replace was the 3 way valve connecting the two tanks and the quick connect attaching the hose to the engine - either one or both certainly could be an issue by restricting fuel since they have not been replaced since it was built - and gum and varnish have a way of accumulating at "choke" points over time. That's well worth checking out!

Thanks also for the heads up on the timing change - at least now I've got a way to diagnose if it is indeed going into "speed drop function", but it sure feels like it. No doubt a fuel restriction could cause the exact same sensation - AND it starts to make more sense since I am not getting the alarm at the same time.

What's the old saying, when you hear hoof beats don't start looking for zebras?

Thanks again for your input - much appreciated especially when you are banging your head on a wall.

[99yam40]

Measuring fuel pressure out of the pump and vacuum into the pump will show any problems and a piece of clear tubing will show if it is sucking air into the fuel system but do not leave it there

[RonKMiller]

Measuring fuel pressure out of the pump and vacuum into the pump will show any problems and a piece of clear tubing will show if it is sucking air into the fuel system but do not leave it there

Excellent, thanks. Sounds like a good first step before I start throwing parts at it. My preferred way of fixing things.

I'm already running a piece of permanently mounted Tygon F 4040 clear tubing from the inlet on the motor housing to the pump so have that covered.

One other thing occurred to me that could be causing a restriction - the new Attwood primer squeeze bulbs I installed. Maybe they were only intended for smaller outboards... Hmmm. Bought them at Walmart. My bad, perhaps a different/better brand would work better? Doesn't seem like the fuel demand would be all that much until you get into much higher horsepower motors.

[99yam40]

I am not sure Tygon tubing is rated for fuel and you will not be able to snuff out a FUEL FIRE easily out on the water when you are abandoning ship if it happens

[RonKMiller]

I am not sure Tygon tubing is rated for fuel and you will not be able to snuff out a FUEL FIRE easily out on the water when you are abandoning ship if it happens

It's designed for all kinds of fuel, although external to the engine I have typical Marine type certified tubing which of course has to deal with additional mechanical demands since it is exposed to UV, flexing, chafing, etc. It's far superior to typical rubber type fuel tubing used for pump to carb connections, oil pump connections, etc.

There is - of course - "generic" and counterfeit Tygon out there which is garbage.

I've actually got FOUR fire extinguishers on board: A big one at the helm and another big one just outside the two rear fuel tank compartments, one mini at the entrance to my trailer and one small under the sink.

I HATE on board fires - I've been a Commercial Pilot for the past 28 years...

at least on a boat you can jump into the water.

Tygon F4040:

http://www.tygon.com/uploadedFiles/S...uel-Tubing.pdf

[Bayliner17yamaha90]

Speed drop issue

My 1987 ETLH 90 is exhibiting a speed drop issue and reverting to "safe mode"... yet the buzzer alarm is not sounding at the same time.

A couple of questions:

1. I checked the thermoswitch with the hot water dip continuity check, it was almost spot on so - that eliminates a bad sensor there. I heated the thermoswitch with a heat gun on low power while connected and it DID trigger the buzzer - as expected.

2. My oil reservoir is half way full and displays a green light, but is it possible the breather (I see they changed the design and eliminated this after 1988 in favor of a different design) on top of the reservoir is plugged and creating a vacuum and restricting flow, thereby triggering the speed drop function? The speed drop function is only supposed to happen when it has less than 0.4 qts in the reservoir, and the alarm is supposed to sound along with the red light displayed on the tach.

3. I recently rebuilt the impeller and have an impressive pee stream at idle but no psi reading. The display shows 5psi when I throttle up to about 2000 rpm but does not climb above that. Should I see a higher and higher psi on the gauge as the engine revs up? IF so I may need to revisit the impeller rebuild even though I feel I did it correctly - or perhaps the connecting water tube is not transporting all the water that it can into the head...

4. Do the buzzer and speed drop always go hand in hand - or is it possible to get one without the other?

Dang, I'm really stumped on this one. Any direction here would be greatly appreciated.

Other than that, the motor runs great!

Picture of my "trailer on a toon" attached for your viewing enjoyment. It was named the "Y knot?"

Hi I got the same engine and had similar problem. Finally found the reason. The diaphragm on the gas pump was broken, causing my engine to stall when I was floring the throttle for more than 3/4. Also, i was getting an oil alarm at full throttle. To fix that, i cleaned the old oil sticking on the net inside the tank with gas and trouble never came back.

[boscoe99]

Hi I got the same engine and had similar problem. Finally found the reason. The diaphragm on the gas pump was broken, causing my engine to stall when I was floring the throttle for more than 3/4. Also, i was getting an oil alarm at full throttle. To fix that, i cleaned the old oil sticking on the net inside the tank with gas and trouble never came back.

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