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Thread: 2.5l mercury overheating
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07-04-2022, 07:08 PM #16
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Smalltownbassin liked this post
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07-04-2022, 07:18 PM #17
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07-04-2022, 07:21 PM #18
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07-04-2022, 07:34 PM #19
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07-04-2022, 07:37 PM #20
Pressure at idle with stats is 5-6psi. Without stats the gage reads zero at idle but the block is full and good strong stream. When rpm goes up so does the water pressure just like it does with stats in and open.
"The character of a man can be easily judged by how he treats those who can do nothing for him"
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07-04-2022, 09:14 PM #21
Not sure if this was mentioned yet , but the divider has been pulled and checked/cleaned for blockage, also adapter plates been checked/cleaned, poppet been checked, head passages r clean , water tube down to pump seal is good. Everything water pressure related has been gone thru least twice , I don't see how we have over looked anything
The only thing cooling wise is diverters don't have any but also didn't come with any
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07-05-2022, 05:24 AM #22
Colder plugs, back off timing, test. I wouldnt be afraid to run a colder plug in that hole only. If that doesnt improve the situation id try some spark boxes from a good running motor if possible. If not a new pair from a different supplier or different type. Seems like throwing darts for this one
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Smalltownbassin liked this post
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07-05-2022, 06:39 AM #23
I can change engine water pressure a couple pounds at WOT by increasing the opening in a restrictor by 1/8". Removing the stats eliminates all restriction creating an open cavity of about 5/8". The pressure has to drop a LOT when they are removed. The fact that it didn't go down indicates a problem, it's not acting as it should.
Living in the Freedom provided by Bud Conner and his fellow warriors.
R.I.P. my Heathen Brother
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07-05-2022, 06:45 AM #24
Yeah thats kinda where im at with it. I was really hoping one of you guys would say "Hey dumba$$, your trigger is toast" or "your SB's are smoking the hole with extra spark" etc. I hate the idea of dropping a grand on new ignition components just to "find" the problem if in fact that is the problem. Not my style. Ill never sleep again if i cant understand what happened and why.
"The character of a man can be easily judged by how he treats those who can do nothing for him"
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Merc 2.5 liked this post
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07-05-2022, 06:53 AM #25
I understand what you mean but the 2 piece plate is restricted by design already. I have one "tell tale" T'd off the stat dumps that ties to the adapter for exhaust cooling. Between the tell tale and the adapter dump ive got between 1/4-3/8 total diameter of open flow exiting. This is much less than what the two stats can flow which in my mind is whats keeping pressure up in the "normal" range at RPM. Just my thoughts on it. Im not saying im right but after going through the flow path, it makes sense for a stock cooling system. Especially with a brand new pump. This is the main reason i dont think its a water flow issue. But...im not certain about it.
"The character of a man can be easily judged by how he treats those who can do nothing for him"
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07-05-2022, 07:35 AM #26
I had a sbc with a gremlin that haunted me for two summers. Couldnt get that thing running consistently no matter what. Finally one day when i popped the air cleaner off i heard a clap that definitely came from the carb. Turned out the vac secondary cam arm was bent ever so slightly and the quick change spring case i installed was ever so little wider so occasionally the secondary arm would catch on it causing a variety of weird. Bent the little arm back straight, problem solved. This was a new carb, that i then sent for rebuild to a highly reputable shop and no one caught it. Sometimes its the smallest things and in my experience its almost always something im 100% sure is good. All i can say is experiences like this has taught me three important lessons. 1. Never let these bumps make you angry or ruin the day. 2. Custom builds are half done the day you first fire. The next half of the build is shaking down and dialing it all in which takes a lot if effort to maximize returns. 3. They’re never done, you simply reach a point of performance satisfaction, for now.
keep your chin up, one change at a time. You’ll find it. In these cases having complete spare parts motors kicking around is invaluable. I have five already, in preparation of my first shakedown year. If your patient good deals come up.
hope some of this helps you outHydrostream dreamin
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07-05-2022, 10:20 AM #27
Enjoy your vids Smalltown!
In the short clip of you checking timing, something didn't look quite right (double time at the end of clip). Maybe try again with engine running, or not, should have nice evenly spaced spark. You can walk the timing light around the flywheel and it should only hit on your index tape or mark on the cylinder your testing, at the timing # that your shooting for. But you already knew that!
Up here in the summer water (70°), I run 140 at idle, when first put on plane they will drop to 100 and work their way back up to 130/140. If I run at high idle in gear, for very long, they build heat, I have seen 170-180. The couple times I had the temp alarms go off my temp gauges read about 185/190. Happened once with lu to high. Again with way to much prop. Another time, eager on the throttle in cold water. Seems they prefer warmed up a long time in 40 degree water, even up on plane and right back off for some more idle time. None of these events left a engine looking like yours.
I believe a switchbox could have problems on just one cylinder, unrelated to trigger. Also could imagine anything connected to em, could potentially damage one. A dva is more conclusive than ohm test when testing sb/stator/trigger.Last edited by OnPad; 07-06-2022 at 08:30 PM.
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07-05-2022, 10:27 AM #28
I don't know if the pics posted earlier with the heads off are from the present state of your engine or when your last one melted number 4... but the piston in that picture is DONE...if that is the present state of your motor I would not run it. The melted aluminum all over the top of your piston can cause predetonition by itself from all the peaks and valleys that get overly hot during combustion. Just my 0.02
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07-05-2022, 02:22 PM #29
Thanks! And i did get some DVA measurements. Stator is fine, trigger pulse was 10-10.2v. CDI spec says 9-10 so im assuming thats ok? Trigger coils ohm all same at 940ish or 0.940K which is inside the .8-1.2K stated in the spec sheet even though its on the low end. SB's are tricky. Only voltage measurement to take is bias on the spec sheet. Its all ohm readings from there and im getting meh numbers. Seems more like im charging or discharging the caps the way the resistance climbs as im measuring. For the life of me i cant make heads or tails of that one. I never saw the double spark myself and ive been trying to capture it. Thats why doing this on video is so helpful. You can see what i miss and point it out. Ill check again this afternoon. Finishing up the second video this week so please keep an eye out for it. Mostly going through the electronics. This thread will help me finish up. Seems like im going to be buying a new set of SB's.....again.
New question- You know anything about old key switches causing a ground fault and killing SB's? Ive heard and read that but never actually seen it. Im wondering if my key switch isnt the culprit and causing me to spend all this money and time over a $20 switch."The character of a man can be easily judged by how he treats those who can do nothing for him"
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07-05-2022, 03:56 PM #30
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