98' Mercruiser 3.0L Drive train interruption. bent push rods etc?

[T4Frog]

Hello all. Many thanks for outstanding advice over the past 4 months, especially to those sharing their wisdom. I decided to take on my first engine complete rebuild for an engine that upon internal inspection should have been scrapped, and wanted to do it by the book. Mercruiser 3.0L had sat idle for 5 years filled with rain water in places water should never be. It was winterized properly, while I was up north, but the boat was not covered allowing water to freeze and get in through the dip stick which started the problem (winter 2013).
In spring 2016 I changed the oil, outdrive impeller and with carb manipulation, got it to run/i looping and rough, concluding it was the sketchy carb. (turned out It was heavy pitting in the 2, 3, &4 cylinder walls).

May 30, 2019, I pulled the engine, free'd the stuck piston rings, found cyl.1-4 psi's of 60, 50, 40, & 25 (more water in the compression chambers back to front from the boat/engine tilt, along with a rusted through front cover. Read a thread for advisement and found that the coolant system held 30psi for 40 minutes before I bled it down and decided to put time into her. When I opened the engine up, the amount of rust top to bottom with rust stalactites hanging off the crank was something to see.

400 backyard man hours, $2100 in parts, $300 for the machine shop tank, bore, hone, and pistons press on later, I took her out for a test run break in. PSI's were now 193, 192, 190, 192. I had bench run, and in the backyard boat run the engine for a total of about an hour at low rpms (1000 or less), working out the bugs and getting the idle, shift, etc., set. It was bay test run day(eve) 9/14/2019 at 7pm. Had the wife steering for 15 minutes from the marina to the bay at 1200-2000 rpms and all was good. Chesapeake Bay was rough and filling nearing high tide 3-4' surge. I took over at 2000 rpms increasing to 3000 rpms over 10 minutes at dusk before deciding to turn back to beat nightfall just in case. All was running beautifully, with a new 14.25x21 aluminum prop, a steady engine temp of 170, and a very smooth running completely open for viewing engine. Five minutes running back about 3/4 mile off the coast against the surge, my boat hung up and rpms went from 3400 to 1000 at 3/4 throttle. I immediately cut her off, tilted the outdrive, although it was getting dark saw the un-fowled prop. I went to start and could not less sputtering. I am a back up plan guy and mounted my old outboard Johnson 15 long shaft as a kicker just in case. That kicker saved our asses at about 10 mph for 30 minutes on the transit back.

When I trailered her and got home about 8:30pm, I went to clean the boat and saw all 3 blades had rebar dents, the anode disc plate had been torn off, the cavitation plate was bent, and the alpha outdrive paint was scratched up in front of the prop. The notorious high tide submerged Chesapeake Bay crab pot had struck again!

Here's where I'm at this morning. Oil is pristine. Pulled the distributor, gear teeth Look good. pulled the plugs, compression test 1-4, 191, 10, 190, 190. I camera inspected cylinder 2 and from what I can make out, cylinder walls look good. piston top looks good and travels with a very small amount of build up, valves and head were difficult to see with todays bright sun but are opening/moving. I hear no clicking while cranking with plugs out, nor did I notice a loud noise upon engine dying on the water. plugs look great.

I'm trying the least involved process of elimination and need some guidance. I'm not a mechanic, but get things done over the years.
My though process: Drivetrain abruptly going from 3400rpms to 1000 or less rpms due to prop fowling means not all parts in motion agree to stop at the exact same time, aka broken gears, teeth, crank, bent valves, metal particles in the oil, stripped U-joints and couplers, etc.

Current guestimation conclusions: skipped/chipped aluminum cam gear or crank gear, sheared cam key/crank key, bent exhaust or intake valve, blown head gasket, cracked head.

I'm looking for knowledge related to the cause and outcome, any new direction to head, and for help with narrowing down the potential problems least to most involved.

Update: Day 2 post crab pot engine damage.

Deeper inspection, after hoping for something mild, I pulled the valve cover. All rocker studs are even hight, pulled push rods out of cylinder 2 and got up to 176psi compression meaning, head gasket is good. Intake valve is able to close, but believe it might have a slight bend. I pulled the camera mirror tip off and mashed it into pieces in cylinder 3, which had a more noticeably bent rod. Been vacuuming out the non-magnetic brass pieces little by little.

My current questions, since I ended up with bent rods, (haven't pulled all 8 yet), and possibly slightly bent valves, but good compression, can I just put new push rods in, adjust the valves, reset timing and drive on with confidence in the engine?? or is there likely more damage and where? I'm thinking the cam gear might be damaged. Not my dream, pulling the engine I just rebuilt (All internals new, less the crankshaft and main caps), but if metal particles, cam gear teeth etc. could have been damaged, I'll pull it. I want it good for the possibility of Gulf Stream fishing.


Thanks,

Ralph

 

[Howard Sterndrive]

190 compression?

Isn't the spec like 170? seems high

 

[Rick Stephens]

190 compression?

Isn't the spec like 170? seems high

I spect that like most non-professional compression testers his is a bit off. Important part is his range hole to hole.

T4Frog, I also spect that you will regret not pulling the head and making sure. You boat in real water. Not sure you have an excuse to halfway anything mechanical. I'd be pulling the drive and inspecting everything I can get to. Pop the top cap, look.And I'd surely pop the top off the engine and have it gone through. If the valves are close enough, a decent machinist won't waste more time on them. If bent, eventually they'll be burnt, and right at the wrong time and place.

Sorry to be a downer. At least you are well conversant in the task.

Rick

 

[T4Frog]

Not sure.. The block face was very lightly planed. I will say, looking back, I didn't figure that in, and for valve adjustment, I took a shortcut after bolting on the head that seemed smart at the time. I paint pen marked the rocker studs and backed off 3 or 4 turns, placed the rods and tightened the nuts back the 4 turns.
Are there any other reasons or negatives for higher compression? I realize that increased compression risks head gasket blowing and possible clearance issues. It is bored out .030 over and I lapped the valves a little heavily. It's been a few months but from what I remember, the new rings came middle of the min/max fitting range and I only had to open one up to match due to one cylinder being slightly narrower. I would guess tighter tolerances can increase compression. My new pistons are flat topped. Now I'm going out to the garage and look at my old pistons to see it they were cupped or flat and my old compression tester gauge I've been using to see if its accurate.

Old pistons were flat topped but pressure gauge does not infect start at zero. the needle os 20psi high so all of my numbers for the build are likely 20 psi higher than reality.

Thanks for helping me to have a look down other directions. These could have aided in the collision.

 

[T4Frog]

Rick,
Thanks for the response and for the bent valve to burnt valve info. I've done a ton and want dependability.

 

[T4Frog]

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[T4Frog]

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[Scott06]

I like the engine stand in the living room!!

 

[T4Frog]

The den was climate controlled, well lit, and cleaner then the garage. Kept the dust out of the bearings and wife loved it :lol:

 

[Lou C]

lucky man there hope you appreciate it lol.

 

[T4Frog]

I'm a little stumped on the findings, with head removed.

I'll try and sum up and update along with posting recent pictures to bring the forum along.

Did a detailed complete rebuild of the 3.0L and she was running nicer than ever before. 30 minutes into test run break-in, running smooth at 170 degrees (with about an hour for compiled driveway low RPM run time on the newly and completely rebuilt engine) out on the bay I hit a submerged buoy and ran a crab pot through the prop at 3400 RPMs. Engine RPMs dropped to 1000 and falling and I floored it (3 seconds) with no response less a backfire. I shut her down, checked the prop. Upon 2 attempted start ups, I had no start, but backfiring.

Engine internals were ALL new, less the crankshaft and the main caps. I kept and cleaned up the rusted cast iron parts with acid baths, pressure washing, scrubbing and wire brushing, to include the block, the head, the exhaust manifold and elbow, water pump, and thermostat housing.

Driveway compression tests pre damage and post damage (note: test gauge is stuck at 20 psi, so I am correcting results):

PRE POST

Cylinder 1: 173 171

Cylinder 2: 170 10

Cylinder 3: 171 170

Cylinder 4: 172 170

Initial conclusion from findings, I bent a or some push rods and valves with the sudden drivetrain jam up.

I loosened cylinder rocker arms and was able to generate a 170 psi in cylinder 2, but not again when I replaced the push rods.

I pulled the valve cover and found one rocker in cylinder 3 nearly off the chewed valve steam seat. the rocker was also chewed on the face. New rockers are here and new valves arrive today. Cylinder 3 compression tests were still fine.

Push rods pulled and rolled on a pane of glass. 5 of 8 were very slightly bent, with only the one from the messed up valve and rocker in cylinder 3 a little more visibly bent.

New rods arrived and put in with valves adjusted. Still low to no needle twitch compression in Cylinder 2, 3 other cylinders coming in at 170 psi. (All rockers seem to be moving as they should and stud heights are correct).

* while checking things week one, I dropped a tin "bronze filled" bore scope mirror tip in cylinder 3, mashed it into 8 pieces while cranking, trying to bring cylinder 3 up to top and then wasted 5 hours fishing all the non magnetic pieces out (successfully). Cylinder 3 has some digs from this, but none no notable crescents from valve collision. I can't rule out the possibility of a slight kiss.

*** I did a leak down test with a Harbor Freight China tester the % loss guage failed, but still showed cylinder 2 did not hold air for even a second with repeated attempts. I then ran in 70 psi on several tests listening to hear where the air was going. I had airflow out the spark plug holes so I put the plugs in, I had air into the exhaust/intake manifold, out the carb and out the exhaust elbow, leading me to believe the valve or valves were not seating. I had a good amount of air bubbling in the exhaust manifold coolant hose, which I could pinch and restrict?? My conclusion possibilities at that point... bent valves, blown head gasket, or the rusted to blockage of flow manifold that I cleaned the heck out of had a crack internally? No air loss noted out of the dip stick or push rod passages.

A negative finding: I pulled the head and was confused. I used a new digital torque wrench to loosen the bolts in reverse sequence and never got above 50 FtLbs so the bolts, which I heavily cleaned, coated with sealant and torqued down with a cheap torque wrench to around 75 Ft.Lbs or more (I saw different recommendations) had loosened significantly.

My additional positive findings,

All cylinder walls are un-scratched and great. all 3 other piston tops, including piston 2 with no compression are immaculate.

I ran the hose and flushed and rinsed what I could the night of the damage. The engine sat with brackish water for 2 weeks now and so some rust in the passageways only. The head gasket and faces showed no signs of damage or water intrusion, although the steel rings around the pistons are slightly misshapen out of round as compared to the cylinder openings in the block. My conclusion, this happens from the torquing compression. I put the gasket on dry and since it has only been on a month or so with little run time, it did not stick to with face, the head or the block and looks nearly new.

My plan... and please stop my if I'm wrong,

Today, I'm going to do a head test that I saw online, With the valves facing up, rockers down, and plugs in, fill the valve bowls up with oil and blow air into the intake and exhaust ports looking for slight air leaks, aka poor valve seating/sealing.

Question: I've never replaced a valve stem guide and have no clue. The valves fit nice and tightly when I replaced them. Engine in all has very low hours on it. Are they likely fine? Any tips?

Next..... Replace all 8 valves with new and a slight lap to seat them. Install a new head gasket, clean the head bolt threading and holes and put the head, new rockers, new push rods, and compression test her. Then install the manifold and drive on if numbers come back right.

Questions..... Do they sell ARP head bolts for this engine or another that also might work for this engine? should I get new bolts? I saw a Youtube video with a pastor who torqued sequentially in increments, but up to 90 ft lbs. I believe the online manuals gave me numbers from 67 to 77 ft lbs with a re-torque after 20 or more hours of use. I now have a good torque wrench and so I was going to re-look up the specs, likely shooting for around 80 ftlbs? Why would you re-tourque on head bolts you have used sealant, which hardens on?

Questions related to the findings and plan and what ever I might not be seeing/realizing.. I realize the head gasket could be much of the cause for air getting by into water passages and that along with bent valves could be showing the lack of compression. What else am I not seeing? Engine rotates smoothly with pistons coming up to TDC nicely and rockers moving accordingly. Distributor stem and gear looks good and rotates as it should. I see this as a mechanical compression issue that is tied to the top end and gasket. I've tried to catch you up without leaving out any information. Please ask if there's something obvious or tricky and not known I might have missed.

Thanks a ton, and I look forward to getting out on the water soon with confidence. Wish I could put videos up!

 

[T4Frog]

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[T4Frog]

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[T4Frog]

New Head gasket and manifold gasket will be here tomorrow. Any chance some of the new lifters could be damaged? rockers are pumping and compressing the new springs.

 

[T4Frog]

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[T4Frog]

Update: Valves arrived. I'm waiting on the head and exhaust gaskets to arrive tomorrow,


I did a head removed Valve leak down test with water in each valve bowl, and eventually 100 plus psi of compressed air from an air gun tip.

Here's what I got. Absolutely no leakage initially for the first 3 minutes on any valve with water in them. Then I went back to cylinder 3, the one with great compression, but a chipped intake valve stem and rounded off intake stem and rocker seat. That valve also had the only one visually noticeably bent push rod..... When I say noticeably, it's not much, but when looking for it, while in your hand, you can see the highest 2.5" are slightly tweaked. That valve seemed sealed well, but I will change it and the rocker and all push rods. I saw a 1mm bubble forming around the smaller exhaust valve lip. I decided to go back and push more air in. Every 10 or so seconds with 110 psi, I was able to make a small bubble rise. It's not worth sweating, but since I crunched up some brass/bronze pieces on that cylinder while testing, I figured, why not change them both.

** My conclusion, with an end result head bolt torque from 40 to 50 ft. pounds, The bolts definitely loosened up significantly, possibly also due to the Mahle/Victor Reinz Mercruiser head gasket set compression caused lower than necessary torquing coupled with the sudden impact stress. The head gasket was under pressure, and possibly that tweaked cylinder 3 intake valve kissing the piston, though from my take, I see no noticeable crescents where they should be on that piston for valve edge impact, the rod was bent and the rocker and seat were chipped and rounded.

Here are my disclaimers: When returning the rocker stud nuts back the 3 or 4 turns it took to get them back to where they were from factory (No planing was done on the head or the block and original valve sizes were used on a low hour engine rebuild), I might have gone 4 or 5 on that valve. It's easy to loose count when things are going so well, or with distractions, etc.
Also using a way off brand tools and Harbor Frieght gasket sealant that had trouble, long delays in time for hardening on the head bolts) might not have been a best choice. Seeking advice from multiple internet sources on torque specs, although you can not necessarily trust the manuals might also steer a person in the wrong direction.

I've got to replace the cylinder 3 valve/s and one rocker arm. The one valve with the chipped rocker face rounded over edge that promotes the rocker slipping off, and the now leaking from a likely ever so lightly scratched exhaust valve seat from mashing the camera scope tip up.

** I'm now most concerned withe the loosening head bolts and head gasket not keeping compression. Did I over tighten it causing the head gasket stainless cylinder ring compression to be weak and the torque to loosen under the strain/higher head pressures?

I'm going with the head gasket failure. Am I missing something?

Can I get some detailed clear cut guidance on head gaskets, head bolts, and the best way from someone with a good amount of experience on torquing and possibly re-torquing them... and some advice on the head bolts and why I lost so much off the torque spec?

Thanks,
R

 

[T4Frog]

Talked with ARP. Apparently they have a contract with "Mercury" and can't help me, but steered me their way. I spoke of the GM engines sharing many similar components back in the day and that the head bolts were possibly the same as the GM V-8's. He said quite possibly. Call Mercury, or get the specs for my bolts and compare to what they have for other engines. Any guidance on this from anyone?

Here is a close up of my head gasket layer over the cylinders showing the misshapened cylinder openings. Is this normal?

 

[T4Frog]

Did some research. Since the bolts look fine and are not Torque To Yield (TTY) bolts, they are to be reused. They also look a great deal like the ARP bolts in shape with their stem step and in color and wear, less them saying ARP on the top. I'm speculating they are a high tensile steel and am going to re-use them, torquing from 30-60-90 ft.lbs. with Quicksilver Perfect Seal thread sealant. The rule of thumb is to re-torque after 20 hours of engine use. I've got some new, high-end "re-useable" Red sealant that is removable without a torch I used on the rod caps. It's called "Vibra-TITE VC-3 Threadmate." Let me try and post a link below. I would love to use this stuff, but I'll probably stick to the long standing Mercury Quick Silver stuff if West Marine has it on hand tomorrow.

 

[Rick Stephens]

Talked with ARP. Apparently they have a contract with "Mercury" and can't help me, but steered me their way. I spoke of the GM engines sharing many similar components back in the day and that the head bolts were possibly the same as the GM V-8's. He said quite possibly. Call Mercury, or get the specs for my bolts and compare to what they have for other engines. Any guidance on this from anyone?

Here is a close up of my head gasket layer over the cylinders showing the misshapened cylinder openings. Is this normal?

Yes, that is normal to every head gasket set I ever saw. Get FelPro Marine sets if you want the best. I bought my last set from Summit Racing.

Note, a Mercruiser Engine is a short block right off the GM assembly line. They put different core plugs, head gaskets and cam in and ship them in huge batches to Mercury to finish up. Things like heads and bolts are directly off the GM line.

 

[Tycer]

New Head gasket and manifold gasket will be here tomorrow. Any chance some of the new lifters could be damaged? rockers are pumping and compressing the new springs.

You can compress the #2 lifters to see if one is frozen. You can swap #2’s lifters with a different cyl. and recheck compression. The new lifters haven’t yet mated with the cam enough to matter. Have you had your spring pressure tested? Are all the rocker studs in line? Are they all the same height? I’m trying to work with the compression without pushrod scenario here.