980 hours on engines - compression test

[harringtondav]

Probably with a bore dial indicator thingy Something like this. . .

An interesting thing in the video was to see how the guy in the video rocks the dial gauge back & forth to find when the tool is perpendicular to the cylinder bore.

You'll still need something to "master" the bore gauge to zero at the spec. cyl bore size. An inexpensive digital caliper will get you w/in .001" to .0005". https://www.harborfreight.com/6-in-digital-caliper-63711.html Set it to your bore size and lock the slide. Then rock the bore gauge in the caliper until you find its minimum reading and zero the dial.

If you don't want to rent, or spring $50-$70 for an inexpensive dial bore gauge set you can buy an inexpensive telescoping gauge set. https://www.harborfreight.com/6-piece-telescoping-gauge-set-5649.html You'll need near surgeon's hands to get accurate, repeatable results. But with practice these will do. Lock the gauge on the smallest bore size and measure telescoping gauge with the digital caliper. $33 and you'll be set to get good hole/bore measurements in the future.

 

[tpenfield]

I do have a 4-5" micrometer as well, as the bore of the 7.4's are 4.25"

 

[alldodge]

Agree, to get accurate readings you need other things then a bore gauge, but to find out how much your bore is dishing out top to bottom, the bore gauge is sufficient. The very top of the cylinder will be original or bored size (top ridge). Every thing from there down will show you how much wear has taken place

 

[tpenfield]

Agree, to get accurate readings you need other things then a bore gauge, but to find out how much your bore is dishing out top to bottom, the bore gauge is sufficient. The very top of the cylinder will be original or bored size (top ridge). Every thing from there down will show you how much wear has taken place

That is a good point. I can take a measurement above the ring line and compare it to the rest of the bore. So, maybe 4 points of measurement and 3 measurements at each point.

 

[tpenfield]

Still practicing with the micrometers. I have a metal ruler, so I took thickness measurements with each type of mic (analog & digital) at the same place along the ruler's length.

Analog = 0.02065"

Digital = 0.02065"

That's crazy consistency . . .

Now I'll have to try for some accuracy. I got an old Briggs engine in the garage . . . maybe I'll take it apart and try some bore measurements

 

[alldodge]

Digital is great for old eyes

 

[tpenfield]

Re-visiting my thread from 2 years ago . . . Obviously, I did not proceed with the re-build and the engines have been running fine the past 2 seasons (2019 & 2020). I have 1,030 hours on the engines, so only doing about 25 hours per season, which is down a bit from years past.

Anyway, I am thinking that this time next year (Fall 2021) I will pull the engines and do a rebuild. Still saving up $$$ for my next boat and that may take a couple more years, so I wouldn't be selling the boat until late 2022 or 2023.

The engines are the Gen 6 version of the 454 - oval port. Is the Gen 6 the Same as the L29??? Not sure about the Vortec stuff either??? I think these engines just pre-date the L29/Vortec by a year or 2 . . .

Since I got 2 engines, and will eventually be selling the boat, I'm planning out a 'low(er) budget' rebuild in that I plan on doing most of the dis-assembly/re-assembly work myself. I am thinking about the following:

1) Send the engine locks and crankshafts out for machining. Hopefully, the bores can be done at 0.030" over and the crank can be 0.010" under. Mill the deck as needed. Install new camshaft bearings.

2) Send heads and valves out for grinding and milling (as needed). Not sure about the valve guides. (I believe that casting numbers on the heads are 10114156), which seem to be fairly rare

3) Inspect the camshaft (before sending things to the machine shop) determine if I should get a new cam or have it machined.

4) After machining buy a 454 rebuild kit with the proper oversize pistons and under size bearings.

5) Assemble the engines, test run, install, etc. etc.

I'm thinking/hoping that I can come in around $2k per engine or $4-5K total. I've seen some threads on OSO and elsewhere regarding a complete rebuild of a 454 and it those were running around $6K/engine . I'm hoping I can come in around $4K, which would make it worthwhile . . . if it were much more, it may not be worth it.

I assume that I should buy new lifters, so wondering if I should just get a cam 'kit' i.e. camshaft and lifters .

My guestimates for the cost of this are:
Engine block machining: $500 per engine
Crankshaft machining: $250 per engine
Head Machining: $250 per engine
Rebuilding 'kit': $750 per engine
Camshaft: $275 each
Miscellaneous stuff: $250 per engine

This would be about $2,275 per engine . . . $4,550 total.

Any thoughts on my plan and estimates?

Since boating season is over in the northeast (USA) I have time to think about these things . . .

 

[Scott06]

My advice might not be as much fun but ... leave them alone . If you’re only getting 25-40 hrs a year ( I do the same in upstate NY) They will probably be fine when u do go to upgrade. Whats your oil pressure at hot idle and WOT?

Certainly whoever you sell your boat to will be getting a very, very well maintained boat, even if you don’t tear into them.

 

[tpenfield]

My advice might not be as much fun but ... leave them alone . If you’re only getting 25-40 hrs a year ( I do the same in upstate NY) They will probably be fine when u do go to upgrade. What's your oil pressure at hot idle and WOT?

Thanks for the input. . . Perhaps not a critical need, as you stated

For oil pressure, I am getting about . . .

Port Engine - 45 psi at idle 65 psi at WOT
Starboard Engine - 35 psi at idle 45 psi at WOT

(per the gauges) Over the past few years I have noticed the port engine running higher . . . Didn't really notice that before.

I am also considering just doing a valve job, which may be most of the issue with compression loss/unevenness. Might only be $500 per engine. I could still pull the engines - clean up the engine bay - check the lower end of the engines and decide if they need work.

Here are the results of my most recent compression test (2020 end of season) as compared to the one done in 2018, 150 psi (red line) is the engines' spec for compression.

 

[louc]

Ted are the engines running smoothly, no misses at idle?
How's the oil consumption?
if no misses at idle and oil consumption is normal then I'd do a cyl leak down test to be sure. If that reveals leakage on the valves for the cyls that tested lower on the comp test, then doing a valve job makes sense. I would leave the bottom ends alone.
On a different topic, we have both discussed outboard boats in the past. From my reading on the Hull Truth, I have learned that they have their limits of lifespan in salt water. That limit seems to be 10-15 years for 4 stroke OBs.
What happens is that eventually you get corrosion between the cyl head or block sealing surfaces and the head gasket. Then water in a cyl & oil and now, you have an engine that is very expensive to rebuild because parts prices are out of sight, and, due to the aluminum construction, it may not come apart without bolts breaking.
So if I went that way, I'd limit my search to engines 5 years old or less. The ironic thing is that if you start with freshwater inboards, and convert them over to closed cooling as you did, they can actually last a good bit longer than outboards, and be far cheaper to repair/replace.

 

[nola mike]

Why not talk to a machine shop first and see what needs to be done?

Ted are the engines running smoothly, no misses at idle?
How's the oil consumption?
if no misses at idle and oil consumption is normal then I'd do a cyl leak down test to be sure. If that reveals leakage on the valves for the cyls that tested lower on the comp test, then doing a valve job makes sense. I would leave the bottom ends alone.
On a different topic, we have both discussed outboard boats in the past. From my reading on the Hull Truth, I have learned that they have their limits of lifespan in salt water. That limit seems to be 10-15 years for 4 stroke OBs.
What happens is that eventually you get corrosion between the cyl head or block sealing surfaces and the head gasket. Then water in a cyl & oil and now, you have an engine that is very expensive to rebuild because parts prices are out of sight, and, due to the aluminum construction, it may not come apart without bolts breaking.
So if I went that way, I'd limit my search to engines 5 years old or less. The ironic thing is that if you start with freshwater inboards, and convert them over to closed cooling as you did, they can actually last a good bit longer than outboards, and be far cheaper to repair/replace.

I always wonder how much of the corrosion occurs while running the engine, how much effect there is wet v dry storage, flush or not after running, etc.

@louc , what happened to you? Changed your name and demoted you with the upgrade?

 

[louc]

no idea!
yeah I feel demoted!
What I learned in my top end overhaul is that the cyl heads suffer more from raw water cooling than the block maybe because they get hotter, and after 15+ years of salt water use the cooling passages get eroded, to the point where a new HG might not seal well. So I keep filling mine up with AF as I've always done, maybe it helps, who really knows.
But I would not buy a 15 year old boat with outboard 4 strokes that old. Asking for trouble. It would have to be newer or re-powered.

 

[nola mike]

What I learned in my top end overhaul is that the cyl heads suffer more from raw water cooling than the block maybe because they get hotter, and after 15+ years of salt water use the cooling passages get eroded, to the point where a new HG might not seal well.

Now that you mention it, all the salt cooled issues I've seen on here are due to manifolds or a few cases of heads worn down. Don't know that I recall many problems with the block corroding. I decided against FWC on my new motor because of that, and because of the little wear that I saw on the 3.7 after 12 years of (admittedly not nearly the same) brackish water use (we're about 10-15 ppt). Keep posting, you'll be back up to your rightful rank in no time. Although I'm pleased that I outrank you. My sig pic seems to be gone, too lazy to replace for now.

 

[louc]

Now that you mention it, all the salt cooled issues I've seen on here are due to manifolds or a few cases of heads worn down. Don't know that I recall many problems with the block corroding. I decided against FWC on my new motor because of that, and because of the little wear that I saw on the 3.7 after 12 years of (admittedly not nearly the same) brackish water use (we're about 10-15 ppt). Keep posting, you'll be back up to your rightful rank in no time. Although I'm pleased that I outrank you. My sig pic seems to be gone, too lazy to replace for now.

I think I had something like 6,000 posts or something! And based on what I saw when I did that top end job I'd agree the blocks seem to suffer less, so replacing the cyl heads at approx 15 years or so, is a way of avoiding a bad hydrolock that could trash the rest of the engine (bent rods).
But if I get a reman or new engine for sure it's gonna be closed cooled. Just for the ease of winterizing alone!

 

[tpenfield]

Thanks for the input guys . . . certainly some things to think about.

The engines are running a full closed cooling system and have never tasted salt water. The engines run fine, but WOT is a bit off . . . . maybe 4200 RPM vs. 4400 previously. My only concerns are that the compression over the years is taking a downward trend, albeit not a sharp decline, and the variations among the cylinders is growing. So, the engines might benefit from some work.

Maybe I'll do a leak test in the spring and see what that looks like.

The last leak test was done during the 2014 compression test as per the results below . . .
Starboard
1 = 11% 139 psi
3 = 8% 140 psi
5 = 13% 138 psi
7 = 16% 140 psi
2 = 10% 146 psi
4 = 9% 144 psi
6 = 28% 139 psi
8 = 3% 143 psi

Port
1 = 5% 149 psi
3 = 11% 150 psi
5 = 25% 144 psi
7 = 3% 148 psi
2 = 3% 156 psi
4 = 17% 145 psi
6 = 15% 143 psi
8 = 3% 150 psi

So, as of 6 years ago, each engine had 2-3 cylinders that were a bit 'iffy'. The compression numbers have gone down about 7-8 psi on average from 2012 - 2020.

 

[nola mike]

What's your goal on a boat that you're selling in a couple of years? Your numbers will be close, drivability isn't an issue really. Don't know what the resale of your boat will be. 50k you might make your 5k back in resale, 15k you won't. Head work might be a good compromise, way cheaper and easier than pulling and refreshing 2 engines.

 

[tpenfield]

What's your goal on a boat that you're selling in a couple of years? Your numbers will be close, drivability isn't an issue really. Don't know what the resale of your boat will be. 50k you might make your 5k back in resale, 15k you won't. Head work might be a good compromise, way cheaper and easier than pulling and refreshing 2 engines.

Good question . . .

My goal is to make the boat easier to sell, but not spend so much doing it that it is not worthwhile. I think a 25+ year old boat with 1,100 (ish) hours and no engine work is a tough sell. Might be $10K of price incentives since anyone buying it would be thinking of it needing engine work at some point.

$2K of engine work (valve job) would certainly be worth it. $4K is probably an upper limit . . .

I'd probably pull the engines even for a valve job, because they are so close together it is hard to work on them. Also, if I pull the engines, I can then clean up and refurbish the engine bay with some bilge paint, etc.

 

[Scott Danforth]

while you have the heads off prior to sending for a valve job, use a die grinder and an assortment of tootsie rolls and rol-loc discs to smooth out the combustion chambers (just remove the casting flash). open up the bowls a bit and blend the valve guides.

 

[tpenfield]

while you have the heads off prior to sending for a valve job, use a die grinder and an assortment of tootsie rolls and rol-loc discs to smooth out the combustion chambers (just remove the casting flash). open up the bowls a bit and blend the valve guides.

I assume turbulent flow for the intake to promote vaporization of fuel and laminar flow of the exhaust to promote evacuation of the cylinder .

I am thinking, as a game plan, to pull the engines after the end of next season (so October 'ish' 2021) and run a set of compression & leak tests. Then decide what engine work to do (i.e. top-end only or lower-end as well).

While the engines are out I can do some re-hab on the transom assemblies and a make-over of the engine bay.

 

[Scott Danforth]

yes, 80 grit on the intake, 200 grit in the combustion chamber and as smooth as possible in the exhausts.

be careful shipfitters disease does not kick in.... otherwise while the engines are out you may go to stroker cranks, build a pair of 496's