Loss of power 0n 1985 90 johnny

[Salty Tricks]

For months this problem has stumped me...and apparently my mechanic too
Engine starts up fine and runs fine when I throttle up on plane. Seconds later she dies and I will not be able to keep it going unless I push in the fuel enrichment button. After months of coming up empty my mechanic now tells me the cylinders are scored. My issue.... is this coincidentally a new problem or could this be the original problem all along? As I said this engine runs fine for a few seconds on plane then dies out. I contest that a if it was the cylinder scoring that it would run poor all the time. Since my 17' Whaler never got above 35 mph (GPS) perhaps the power was always not up to optimal and the above is another problem. I sure would like to get another year out of this motor?

 

[fireman57]

Re: Loss of power 0n 1985 90 johnny

Sounds to me like you have a clogged jet or your fuel pump is weak. If you have to hit the button then you are starving for fuel. That means that you are also starving for oil which lubes the cylinders. You might take the carbs off and check the reed valves for an obstruction. Do a compression test and post the numbers. I don't think that the scoring is your original problem I think it is an effect of not enough fuel and hence lube.

 

[tashasdaddy]

Re: Loss of power 0n 1985 90 johnny

check the compression on the motor. 100 psi or above, and within 10 % of each other it will run. higher is better as long as all equal. enriching the fuel, says it has a fuel restriction somewhere, and sort of rules out electrical. are you running a built in tank, is the vent clear, or portable is it open? when were the carbs last cleaned jets removed, and reassembled with rebuild kit? are you sure there are no air leaks, in the fuel line. test the fuel pump. also has any one messed with the linkage. the link N sink could be off. this synchronized, the spark, with the carbs, so they work together. could be flooding, as spark is not advancing. was that enough to total confuse you? are you sure your mech is up to date. that 1985 is just broken in, proper care it will out live you.

 

[Salty Tricks]

Re: Loss of power 0n 1985 90 johnny

I rebuilt carbs two years ago, linkage was never touched as far as I know. motor ran great after I did carbs but that was different symptom since then I couldn't get on plane but it wouldn't die. Then, the fuel enrichment would get it on plane. Now the fuel enrichment just keeps it running and gets me back to the dock. I have a gut feeling that the cylinders were scoured before this problem. I did a compression test two years ago and it was 115 on all four. time to start with a new compression test and see what I got.....I'll be back

Thanks for the great ideas.

 

[Salty Tricks]

Re: Loss of power 0n 1985 90 johnny

Okay Folks here's my compression results

Cold motor, throttle open:

Left 2 cylinder read 95psi
Right 2 cylinders read 100psi

The left head is the head that was removed by the aforementioned mechanic. I bolted it back with existing head gasket and I didn't torgue the head bolts.....could be the reason why those two are slightly lower.

Nonetheless doesn't this indicate that my original problem is not being caused by scoured cylinders. Also, based on the compression results, is this engine now worth sinking some money into such as a new fuel pump (I'm gonna try getting an earlier non VRO pump), all new fuel lines, possible new fuel tank (this one is a fiberglass Pate tank which could be suffering from the use of 10% ethanol) carb rebuild etc?

Thanks for all your continued help

 

[OBJ]

Re: Loss of power 0n 1985 90 johnny

The reuse of the head gasket will cause a low compression reading. Get a new one and torque the head to specs.

I think T-daddy hit it on the head with fuel restriction. I believe I'd go for the carbs.....a good soaking and rebuild. And unless your seeing some physical or audio signs of the VRO being bad and the cylinders look good, stay with the pump. Just make sure the connections are tight at ends.

 

[Salty Tricks]

Re: Loss of power 0n 1985 90 johnny

Thanks OBJ

However do these numbers indicate that mechanically I still have something to work with ??? I did feel some slight irregularities on the cylinder walls though. I didin't open the right side yet. I was hoping these numbers would be sufficient to start considering repairing this motor instead of looking for another.

 

[OBJ]

Re: Loss of power 0n 1985 90 johnny

Your numbers sound OK Salty. Not sure what you mean by "irregularities" on the walls. If I can slid a finger nail around with out catching, I feel the walls are good to go. Can you see any scuffs or cuts in the walls?

 

[Salty Tricks]

Re: Loss of power 0n 1985 90 johnny

I can feel some minor ridges running from top to bottom in the cylinder bore on both cylinders. Both are on the gearcase side of the bore.

Also you recommend keeping the VRO. I was inclined to swap it for a non VRO and go with pre-mix. This would also make it easier using the 1980 15 hp Johnson I have for a kicker. I also think I'm flirting with disaster depending on a 22 year old pump (assuming it's original)

 

[Salty Tricks]

Re: Loss of power 0n 1985 90 johnny

I posted a similar question on another site and a response suggested that this motor should be up around 130 psi and that it will not run very well at the numbers I'm getting. I am not trying to play you guys against each other..just trying to ascertain whether this motor deserves some money and time or it should be scrapped. Thanks for your input.

 

[hoeser]

Re: Loss of power 0n 1985 90 johnny

That engine will run with those numbers. If you have to choke to keep running you are for sure starving it and it will lead to eventual damage, though as it sits now once you resolve the issue I wouldn't be worried about your compression numbers. You'll definitely want to retorque that head and put a new gasket following the appropriate torque pattern.

 

[Salty Tricks]

Re: Loss of power 0n 1985 90 johnny

Thanks Hoeser

I think I'll focus on the fuel system and delivery. Wiil certainly buy head gaskets and re-torque.