87 NS25C2 Rough Idle, Rough Mid Range, Fine @ WOT

[MrTotty]

I will check the reed valve case nuts for tightness. , I did spray carb cleaner around that and had no change. I'll pull the flywheel and other assortment of goodies and check/replace that seal. If thats not leaking my only guess is the carb is just wore out, I found it odd that there was a sharp point at the end of the dip on the throttle cam, I'm wondering if it didn't wear that way, if that was the case that could also explain the leaking around the butterfly. Be nice if I had some parts laying around to test. These parts go for a premium, even used.

 

[Sea Rider]

Can you post a pic of the old throttle cam to have a look at the sharp point at the end of the dip on the throttle cam ? The only way you can wore throttle cam & butterfly would be if having an excessive over cam actuation during long years running wot . Can you measure the rod distance of the timing flywheel plate & arm in mm with the vernier's point side used to measure internal diams.

With new ignition/carb adjustment, you have set timing mark to 25 deg and full 180 deg butterfly right ? when holding carb's pawl at max height and when throtteling to wot back and forth, do you hear a very light bang sound when cam bangs against white roller ? As to check if with over cam/carb actuation.

Happy Boating

 

[MrTotty]

The old cam is posted on Page 1 of this thread, you can see the dip that I am speaking of, I've only owned this motor for about a year and of that year it's only been running the past couple of months, I have not idea how it was run before I bought the boat it came with. I'm not sure what you mean in your measurement request.

I do have it set to 25 deg at full 180 deg deflection of the butterfly, I do know you can move the throttle plate a touch more than the arm moves it, so it's not binding if that is what you as asking. I've got a stock throttle plate (as well as a ball joint that I broke) in the mail and will replace that when it arrives.

I also replaced the upper seal last night, it did have quite a bit of oil residue around it, my guess though is if it's leaking it may be coming from the crank case halfs. From what I can see there is no paper gasket between them, only permatex? If that is the case, I'll have to order a new powerhead gasket to remedy that.

I think I'm close to closure on this, but I don't like being close, I like it being right... Thank you for all of your help so far.

 

[Sea Rider]

The upper timing rod distance should be around 35.0 mm as in pic. check yours. Which color are your actual rod snaps, white or black ? There's no gasket in middle ckarankcase's halves, are sealed with permatex only. The groove on old cam probably came so, a matter to compare it to a new one, that's why was assuming a probable over cam actuation against roller.

BTW, how are all your throttle plastic parts from tiller throughout the whole trottle mechanism, have excesive side play ? Tohatsu 25-30 HP throtttle mechanism is simple, cheap and fast to repair, but with time they due wear out fast if not lubed/greased frequently..

Happy Boating

 

[MrTotty]

My upper timing rod has two black ball joint caps, I will have to measure the distance on them as I have it set now. I would assume it gets measured from the inside of the nut to the inside of the nut.

I have not noticed any play throughout the throttle, I don't use a tiller, this is a remote setup. I did notice the lube was very stiff on the advance ring, which I cleaned off and re-greased with some marine bearing grease, works much smoother now. I should get my first shipment of parts today with the throttle cam, I'll make sure it's all lubed correctly when I replace the homemade part. I did break one of the white snaps (which I ordered more) as well as a ball joint cap (which was the second order).

 

[Sea Rider]

The timing is measured :

ext nut--------------rod--------------ext nut = 35.0 mm or near it.

Happy Boating

 

[MrTotty]

Mine is in the 20MM range, I don't think I could even get 35 out of it. Mine does have double ball joints instead of a snap on one end. at WOT it's sitting at 30 Deg timing, at idle it's sitting at 0 I would assume that is correct. The upper seal didn't change anything, I've checked and rechecked all other leak points I can find, the only thing I can think of is something is wore out on the Carb. I'm keeping my eye out for a replacement carb that someone does not want 200.00 for. My guess is that might be my answer. Other than that I may just run it like it is and see if run time helps.

 

[MrTotty]

While running on Saturday it ran fine up the river, then started acting the same as before (cutting out) coming back down river. I had cleaned the block while looking for leaks, and noticed oil coming out of the left side of the crankcase where the two halves meet. I've pulled the power-head, and will split the case and reseal. I'm hoping at this point it solves the issue. While the power-head is out I will re-torque the head bolts. Do you know what the torque spec is for the crankcase bolts?

 

[Sea Rider]

If parting cranckcase in halves to re seal properly, take advantage to manually decarbon both piston heads and cylinder head as well. Once new carb cam is changed and stopper A correctly adjusted to achieve 180 deg butterfy, adjust timing to 25, 30 deg is too much, will have excessive timing for the max fuel entering engine while at wot, not good for engine.

Open/close rod nuts untill correct timing is achieved, If carb has front butterfly with slight worn casting, not an issue, if rear small butterfly with excesive rod side play, will have idle issues.

Cylinder head torque is 30 Newton/Meter, don't forget to re torque manifold nuts and lateral exhaust lid/cover with wrench bit tight. Post your findings, water tests results.

Happy Boating

 

[MrTotty]

I was wrong, I was running at 25 Deg timing (up from 20). I split the halves tonight and found another issue. When i pulled the read cage off to remove the two bolts, a screw fell into the bottom of the block (that I didn't take out). The screw that holds the labyrinth packing had apparently backed out, enlarged the hole in the lower half of the crank and wedged against a reed valve. It's been this way for a long long while, it wore a nice little divet in the inside of the reed plate cover, and wore the reed stop in a spot, there was one tiny little place on one of the reeds that you could see it rubbed against, but no damage. I bought a new bolt, used red loctite, and put some oil/gas safe epoxy to help keep the screw from moving, it all went back together well. I'm wondering if that bolt wasn't keeping a reed closed. If that screw would have fallen into the motor with it running it would be scrap. I'm awaiting the gaskets to put it back together, The head was decarboned when I replace the head gasket. I also noticed that the upper bearing was spinning on the crank (inside race). The crank looks to be slightly worn, I put some red loctite on the shaft and replace the bearing (suggested by a mechanic friend of mine). I am beginning to wonder if this motors days are numbered.

 

[MrTotty]

Got the motor back together tonight, It seems to run better. I think I still have a touch of adjusting to do on the low end needle. It seems to run much much quieter than it did before. I also noticed that now the water is clean in the trash can where before it would be milky and have oil sludge floating in it. May have the idle set a tad to high as well, need to get a Tach to check that.

First video is how it ran after I replaced the head gasket

 

[MrTotty]

This is how it ran after I put it back together tonight.

 

[Sea Rider]

Sounds good, after engine is quite warm go for a 3-5 minute wot spin prior adjusting pilot screw. The factory delivered setting is usually 10-10,5mm measured from top mixture screw to base at 6 o'clock position, measured with a vernier's back indicator (Upper screw/base)

Idle rpm speed on that engine measured with an induction tach is bit erratic, adjust to a point engine doesn't die when geared forward. Adjust till engine pushes well boat at min idle speed. Can do it inmediately after finishing with pilot screw adjustment.

Happy Boating

 

[MrTotty]

so thats 10-10.5mm from the top of the screw to the edge of the screw hole? I've got a new needle, I'll try that when I replace it.

 

[Sea Rider]

so thats 10-10.5mm from the top of the screw to the edge of the screw hole? I've got a new needle, I'll try that when I replace it.

Yes, measured top screw head straight to base at 6 o'clock, this lower part has more flat surface than measured at 12 o'clock. With pilot screw set at 10 mm should idle well and even once engine is fully warmed up. Readjust idle speed screw as recommended if needed.

Happy Boating

 

[MrTotty]

I took the boat out to go fishing and the motor ran pretty bad in the mid range, it had issues getting to WOT some of the times, I would have to pull back on the throttle, then reapply to get full power (as seen in the video). Once I got the boat back home (awesome day fishing btw) I changed the throttle lever which I can't remember which was which. I bought both one for the NS25C2 and the NS25C3. This may have fixed my mid range issue (have not water tested yet), but the throttle response difference was huge. I rechecked the compression and found that I was reading the gauge wrong. It looks like i have 110 in the upper cylinder and 102-105 in the bottom which may explain my rough idle unless you think it should idle fine with 5 PSI diff.

 

[MrTotty]

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