Almost there on that 25 HP 1989.

http://www.marineengine.com/boat-forum/showthread.php?412918-More-help-needed-on-that-25-HP-1989
Link to last thread for reference.

Got it to the lake today. WOW, I think Graham was right. It flies. Easily 25+ MPH
But it isn't quite perfect.

I tried trial and error timing adjustments.

Basically where I am at now is the last bit of throttle it starts to shudder and bog down a little.
When I first started today the "spark advance link rod" was about where I though it was by the coloration of the threads and it was about centered.
I slowly adjusted the "spark advance link rod" shorter and shorter. It kept getting better. I ran out of shortening room.
It starts, idles and gets up to nearly WOT until it starts to fall back and shudder.

Is it time to buy a timing light and tiny tach?
I will re-size some pics and upload to see if that can help anyone help me.

Thanks again.

Jim

Adding pics.
This in in neutral
This is about as good as it gets but going very fast.
This is WOT. It shudders and bogs down here. There is only a small twist of the throttle handle to get from pic2 to pic3.

If you really want to "tweak" this you will need a tiny tach (or similar) and a timing light.

It's suicide to try and time the wot setting without a proper tank and a test wheel (prop) but you can time these at 3000 rpms (not on a flusher but in a garbage can full of water or with the boat on the trailer secured at a launch).

AT WOT the timing should be 25 degrees before top dead center (3 dots on the flywheel if yours has the dots instead of the numbers - each hash mark is 2 degrees).

At 3000 rpms you can time it at 28 degrees BTDC (the timing light would "freeze" 1 and half "hashes" to the left of the 3 dots on the dot marked wheels) and at 5500 it will retard the 3 degrees down to 25 where you want it.

Guys thanks again.

Tiny Tach is on the way, and I will be getting a timing light very soon. This one does have big white dots on the flywheel.
I removed the entire power head and resealed it on Graham's advice over the winter. Seems he was right.
Setting it at 3000 seems way safer than WOT. I don't know about the tank timing setting. It will loose a lot of water fast.
The lake I was at yesterday isn't busy and if I go during the week, I may be able to do it on the trailer. Triple wide launch and no docks.

I never would have considered sealing an engine that looked like you could eat off of it.
This shows there is no substitute for experience.

Thanks again. I will report back as soon as I get it tweaked in.

If you are working from a "garbage can" test tank you can disconnect the shift link so that it doesn't go into gear (just pop the rod off the ball on the shift) - that way you can wind her up (to 3000, and only for short periods to check the timing marks), without blowing all the water out of your can with the prop.

Do you guys have factory manuals or something?
How do you know 28deg. BTDC is equal to 1.5 hashes to the left of the 3 dots?
Just curious.

I would rather try the tank method out of gear. Thanks for that tip!!
You guys are the best. I will get this perfect even if I die trying.

I have both the service manual and a Seloc's - they both have their advantages.

If you would like the section (service manual) on the timing etc just drop me an email ([email protected]) - make the subject something obvious (like 25 horse timing) and I will send ya a pdf file.

OK, crappy timing light and not sure of the correct setting for the Tiny Tach. 180 or 360?

From TinyTach manual.
180 says 2 sparks per revolution.
360 says 1 spark per revolution.

Set at 360 it is in neutral and idling about 1200 to 1500? Close to the 4 dots on the flywheel.
I think 180 is the correct setting, but shooting the timing light with (TT set on 360) 3000 RPMs the way it is set now, I don't even come close to the 3 dots.

Lengthening the rod all the way was as close as I got. About 4 hash marks to the right of the 3 dots.
On the lake I had the rod completely shortened, which made the shudder only happen very close to WOT.
There must be something I am missing?

No Jam Nut (13A?) on this engine. Just pop and turn. I have been messing with part #12 for quite a while.

It should reach max advance around 3/4 throttle

Click to expand...

It is still moving all through the throttle range, so something is not right.

Yes I am using plug #1, top one.

I think I am starting to understand this.
This will be a 2 person job for sure.

I may decide to put the engine on my big boat. It will be much safer. Only issue is it is a short shaft on a 20" transom. My kicker I cannot run at WOT or it will suck air into the prop.
If I get a couple of people in the back though it may work.

Thanks again.
Jim

Tiller.

Boat I am hoping to use it on is a typical 14' Starcraft with a severely beefed up transom (done by me).
It is a 13P prop currently.
Previous boat was a beefier 14' with deeper hull, similar but certainly not the same.

..."time to buy a timing light "

I hope you did. Running too much advance (what it sounds like) eats pistons.

Jeff

OK went to the lake and let her rip.

I put the timing adjustment rod (part#12 back to its original location. This was because with the rod shortened all the way, RPMs exceeded 7.5K.
With the rod about centered, the 3 DOTS appeared about 2 hash marks to the LEFT of the mark on the starter cover at 3000 RPMS.
It starts to shudder at 3600 RPMs doing 17 mph.

Idle in neutral is about 1100 RPMs.
Idle in gear is about 800 RPMs.

At 3000 rpms you can time it at 28 degrees BTDC (the timing light would "freeze" 1 and half "hashes" to the left of the 3 dots on the dot marked wheels) and at 5500 it will retard the 3 degrees down to 25 where you want it.

Click to expand...

Graham, did you mean to say right and not left?


1 and a half dashes to the left is about the end of the timing marks. There is only one mark left.
What are all the other dots for?
I am going to try a 15P prop if I can find one locally.
My wife is in NJ now and I am having her get the specs off of the POs boat.

Thanks again, I will get this.

Jim

Current prop is marked,
48.19640 A10L 13P

Yes, sorry, 1 1/2 hashes to the right (when I "think" about it I always get things backwards - you are working with BTDC, so moving to the right is (less) closer to dead center - 28 BTDC would be "left" of 25 BTDC - ok, I'm straight now - one of those things when you are doing it, I know what I'm looking at/for )

Sounds like your current prop is a 10.375" (10 3/8") Diameter, 13" Pitch.

Altering the diameter has (almost) the same effect as altering the pitch.

Moving up from a 10d13p (current), to a 10d15p would typically drop your top rpms by 400 from whatever they are hitting now.

So, likely my timing is OK, and a different prop isn't going to do anything for me.

I may take it back to the lake tonight. I literally had it to myself last night. When I had the rod shortened (retarded all the way) the Tiny Tach was still bouncing all over (5000-8000 RPMs).
I managed to reconfigure the tach so it was steady. I need better readings from the tach as I retard it further, which is where it runs best.

How can I diagnose this? Am I dropping a cylinder? Some wires arcing over?
What ever it is, it is consistent. Should I pull the flywheel and recheck everything under there?

More Info.


I did some general ignition testing.


Stator = 3040 ohms
Trigger = 747 ohms
Both primary ignition coils = short
Top secondary coil = 919 ohms
Bottom secondary coil = 915 ohms


All are in spec. except the stator which is very close.




Spark plugs are B8HS-10 gapped at .040.
Why these are in there (I put them in)?
Service bulletin says they should be NGK BP8H-N-10
Could this be my issue?


I rerouted some wiring, and will try to retest this weekend.
After this I may start shotgunning parts, starting with coils and wires.
At least on these new engines they are available.

I am shotgunning the coils and ignition wires. The Sierra coils came with these tubular looking ferrites.
Where do they go?

Thanks
Jim

You don't need them.

Those coils can be used with the 6 horse motors on up. The 15 horse and below mount the coils with a bolt right through the coil body (that hole in the middle of the coil).

Your 25 should want them mounted with the case over them installed in the (holder) on the motor itself.

So just install them and forget about those insulated sleeves that came with them - not for your model...

Awesome, thanks again.

I may get there. 2+ years now on this engine. Carb. is now flooding badly.
Popped it open, floats don't float very well when full of fuel.
How many issues can one engine have?

jim18611865 said:

How many issues can one engine have?

Click to expand...

Couple of years back I took my 15 horse up north fishing - last 150 miles on a single lane logging road - so miles from civilization/dealers etc.

Loaded up and boated out to the island we were camping on - throttled back coming into the shore and blew the gasket on the intake transfer cover (down to 1 cylinder and a bit of the second - lower cylinder).

Horsed around with the timing/throttle adjustments enough to keep it running (like a wet dog on a freezing cold day). Ok, can live with that. Two days go by and I blow the upper crank seal - now my 15 horse is running more like a 5 horse.

Still managed to salvage the week with my "trolling motor" that was blowing raw gas everywhere.

Got it home. Replaced the seal and the gasket. Tried to re-sync everything - still ran like crap. Had a carb kit - it had never been done and was a 1991 model so figured it couldn't hurt - threw in the kit including fuel pump kit.

Fired it up, tweaked everything and noticed it had developed a "miss". Was about to shut her down and replace it with one of my 9.9's when I heard the "snapping" sound - lower coil was throwing lightning bolts.

Pulled the coils and gave them a good wipe down. Both cases were spider-cracked badly. Over to the Sierra dealer for a new pair of coils.

Moral of the story - sometimes one thing leads to another - oh ya, got her fired back up running like a top - tuned perfectly and she stopped pumping water. Impeller was a year old - pulled the lower unit and the waterpump cover seal (where the water tube enters the cover) was missing a giant chunk.

She has ran fine all of last year and this year "so far" - so there is light at the end of the tunnel - just sometimes it says "EXIT"

...."She has ran fine all of last year and this year "so far" - so there is light at the end of the tunnel - just sometimes it says "EXIT"

And sometimes that light is from an oncoming express train!

Jeff