1999 Mercruiser 454 Horizon Inboard Valve seats

Discussion in 'Mechanic Recommendation Forum' started by West32, Oct 15, 2018.

  1. West32

    West32 Active Member

    114
    May 24, 2017
    Racine
    1999 Sea Ray 370 EC Hardtop
    Raymarine Axiom Pro system, AP, Radar, VHF, Fox Marine Engine Monitor
    Twin Mercruiser 454 Horizon 380 hp
    I purchased a 1999 Sea Ray 370 EC with 3500 hours on it in July of 2017 knowing the port motor had issues. When I finished the 2017 season, I pulled the motor and brought it to a very reputable motor builder. He went through the entire motor and found the Cam was bad (Wiped Out). The bottom end was perfect, so he honed the cylinders, put new rings on the pistons,New bearing, Cam, new oil pump and did a valve job... I put it back in the boat and it ran great. This year I noticed performance starting to go down throughout the year. I did a compression check and found 125 to 130 across all 8 cylinders. I pulled the motor and brought it to him. Everything inside looked great except for the Intake Valves. All 8 intake valve seats showed a gap on 25% of the seat next to the Exhaust valve. There were NO signs of heat build up anywhere. Nothing was discolored. Nothing smelled when he pulled it apart.
    Has anyone ever heard of this? The engine ran about 125 hours with 100 of them at Idle Trolling for Salmon. It never ran over 4000 RPM for more than a few minutes ever. Cruise speed is around 3500 - 3700 RPM. I did use a lot more fuel in that motor throughout the year too..

    Thoughts? What are we missing?

    Would like to figure it out before we put it back together again...
     

    Attached Files:

  2. joeyleggz

    joeyleggz Active Member

    526
    Jan 15, 2013
    long island
    current boat: 1997 sea ray 330 express cruiser
    twin 454's efi
    Sorry to hear about your problems I have a 97 33 express cruiser with 454’s repowered both my motors last year have about 80 hours on them now with no issues what I did hear from mercruiser is that at idle for prolonged periods of time meaning 30 minutes or more a good practice is to bring the RPMs up to around 1200 to 1500 for a minute or so and let it burn off and push out any condensation or misting water droplets that get drawn back in to the exhaust valves From the exhaust pulses which our motor seem to have problems with. There was a mercury bulletin about adding resonators to break up the exhaust pulses so that you do not get the back pressure of sucking in and ingesting water droplets So that might be a possibility with over 100 hours at idle speed other things that come to mind would be a bad head job did he redoo the seats in the heads? And what cam did he put in ?possibly with the wrong clearances maybe the valves are slamming into the seats a little harder? Just throwing this out there
     
  3. joeyleggz

    joeyleggz Active Member

    526
    Jan 15, 2013
    long island
    current boat: 1997 sea ray 330 express cruiser
    twin 454's efi
  4. West32

    West32 Active Member

    114
    May 24, 2017
    Racine
    1999 Sea Ray 370 EC Hardtop
    Raymarine Axiom Pro system, AP, Radar, VHF, Fox Marine Engine Monitor
    Twin Mercruiser 454 Horizon 380 hp
    There was no evidence of water intrusion into the system. The boat was previously used a salmon fishing boat and the starboard motor now has over 3700 hours of mostly idle running with still very strong compression (155 average). Bad head job? Maybe, this guy does around 200 motors a year. He has GREAT references. He is as baffled as I am. Nothing shows signs of Heat damage. The only thing that might have some credibility is Timing. Maybe the ignition module is not advancing at higher RPM's? Maybe? It was Running VERY good at the beginning of the season.
     
  5. hottoddie

    hottoddie Well-Known Member

    Jan 11, 2012
    Boston/Cape Cod
    1986 Sea Ray 390 EC
    Garmin 4212 Chartplotter
    Garmin 24 HD Radar
    Garmin 546s Plotter
    454 Crusaders
    What is the rated max rpm? Cruise on gas marine engine is usually 70-75% of max rated rpm. I cruise mine at 3200 max but aren't Horizons and max out around 4200.
     
  6. West32

    West32 Active Member

    114
    May 24, 2017
    Racine
    1999 Sea Ray 370 EC Hardtop
    Raymarine Axiom Pro system, AP, Radar, VHF, Fox Marine Engine Monitor
    Twin Mercruiser 454 Horizon 380 hp
    WOT RPM is 4400 to 4800 RPM. I can get to 4600. I cruise around 3300 to 3500
     
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  7. West32

    West32 Active Member

    114
    May 24, 2017
    Racine
    1999 Sea Ray 370 EC Hardtop
    Raymarine Axiom Pro system, AP, Radar, VHF, Fox Marine Engine Monitor
    Twin Mercruiser 454 Horizon 380 hp
    This was on a calm day running 25 MPH Engines seemed happy. Notice the port motor GPH vs the Starboard.... quite the difference


    1530646098365.jpg
     
  8. PlayDate

    PlayDate Well-Known Member

    Dec 25, 2006
    Washington DC
    1994 370 Express Cruiser
    454 Mercruisers
    Your eyes are better than mine: What is the GPH on each motor? RPMs look to be 3200?

    In regards to the Starboard motor.....that is great compression for 3500 hours. For the rebuilt port motor.....do you have a photo of the valve seat?

    Since you lost power over time.....I would check the new cam (lift and duration), lifters, rocker arm geometry and valve guides for a problem. It could have been a break in problem with the new cam which caused the loss of power over time.

    Have your guy also check the oil for metal.
     
  9. PlayDate

    PlayDate Well-Known Member

    Dec 25, 2006
    Washington DC
    1994 370 Express Cruiser
    454 Mercruisers
    Great video BTW. I love the sound of big blocks running.
     
  10. West32

    West32 Active Member

    114
    May 24, 2017
    Racine
    1999 Sea Ray 370 EC Hardtop
    Raymarine Axiom Pro system, AP, Radar, VHF, Fox Marine Engine Monitor
    Twin Mercruiser 454 Horizon 380 hp
    17.8 GPH on port vs 16.2 GPH on Starboard.
    He said the Cam looked fine. All 8 intake seats had about a gap towards the exhaust valves..
    He also told me I had a broken Guide plate.
    The cam was the issue on the original build with 3500 hours. The cam was worn down over 1/8 of an inch on the number 5 cylinder....
    This is a Horizon motor with Roller lifters
     
  11. hottoddie

    hottoddie Well-Known Member

    Jan 11, 2012
    Boston/Cape Cod
    1986 Sea Ray 390 EC
    Garmin 4212 Chartplotter
    Garmin 24 HD Radar
    Garmin 546s Plotter
    454 Crusaders
    Assuming the flow meters are accurate the difference in fuel use is about 10%. There are a few things that can account for that. Counter rotating transmission, ignition timing, props, faulty injector and overall engine condition IE compression. There is usually some difference in fuel consumption between engines.
     
  12. PlayDate

    PlayDate Well-Known Member

    Dec 25, 2006
    Washington DC
    1994 370 Express Cruiser
    454 Mercruisers

    When you say gap.....what does that mean? Does that mean the intake valves were not seating properly? If that was the case the engine would have been backfiring continuously.

    It is time to do a leakdown test on the engine to determine if the heads or the block is the problem. I'm suspect of honing a block with 3500 hours on it. Any block with that many hours probably should have been bored to get the cylinders round. That could be the compression problem since the new rings would seat for a while then start to bleed compression.

    In any event, a leakdown test will prove what is bleeding compression. All it costs is a set of head gaskets and you don't need to do anything but bolt the heads onto the block, tighten them down and find TDC for each cylinder to test it.

    Your guy could be great and I'm trying not to second guess him but he knows a leak down test would identity the compression problem in seconds. The air either goes through the valves or past the rings.

     
    joeyleggz likes this.
  13. West32

    West32 Active Member

    114
    May 24, 2017
    Racine
    1999 Sea Ray 370 EC Hardtop
    Raymarine Axiom Pro system, AP, Radar, VHF, Fox Marine Engine Monitor
    Twin Mercruiser 454 Horizon 380 hp
    When I brought the engine to the builder the first time, he disassembled and miced up everything. The cylinders had little to no wear and the factory cross hatching was still there.
    This year, the builder did do leak down test and the intake valves proved to be the culprit. The valves themselves looked fine and in fact were measures and put on the valve grinder and found to be perfect. The valve seats were the real problem. The deformation on the seats were limited to a small area adjacent to the exhaust valves. The question is why did this happen. After the motor was rebuilt last year, it was put on the dyno and proved to run within specs. The beginning of this year, the engine performed as good or better than the Starboard motor, but as the year went on, the performance started dropping fast. Please note that this motor idles most of the time. The engine ran about 125 hours with 100 of them at Idle Trolling for Salmon.
     
  14. PlayDate

    PlayDate Well-Known Member

    Dec 25, 2006
    Washington DC
    1994 370 Express Cruiser
    454 Mercruisers
    That is helpful although I have never seen a block with that many hours that didn't need to be bored.

    That said....the leak down test showed the intake valves seats were deformed so let's go with that:

    Normally that is accompanied by a heat problem (cooling) and/or lean condition issue. The head material is softer than the valve so the head will distort before the valve does. So the $1,000 question is why did the heads deform consistently at the same spot?

    The only thing that will distort/damage the head is heat. Unusual heat comes from a lean condition which your ECM compensates for by adding more fuel and creating more heat. You saw this on your fuel meter and my guess is that this got worse over the last 100 hours of use.

    Vacuum leaks will create a lean condition that will affect all cylinders and cause their temperatures to rise. It would take something like this to cause a problem like this across both heads in the same spot. An ECM will cover up a problem by adding fuel for as long as it can until it exceeds its parameters.

    I'm not sure how visible the heat of this nature would be on the heads. The valves would definitely be gray but the seats probably would not look off.

    Is your guy going to replace the Intake seats in your heads? The good news with that is that a replacement seat is much harder than the cast iron and won't deform. That will solve the compression problem. When you put it back together just make sure everything is tight on the intake and plenum.

    I did make one assumption that the replacement cam has the same specs as the one it replaced. Hopefully that is the case.

    I hope this helps.
     
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  15. PlayDate

    PlayDate Well-Known Member

    Dec 25, 2006
    Washington DC
    1994 370 Express Cruiser
    454 Mercruisers
    One last thought.....since most of the hours are spent trolling....I would speculate the damage was done trolling which means you should probably replace the IAC valve since it manages vacuum at low RPMs. I'm not sure that is the problem but it is cheap insurance.
     
    hottoddie likes this.
  16. West32

    West32 Active Member

    114
    May 24, 2017
    Racine
    1999 Sea Ray 370 EC Hardtop
    Raymarine Axiom Pro system, AP, Radar, VHF, Fox Marine Engine Monitor
    Twin Mercruiser 454 Horizon 380 hp
    I did replace the IAC valve as I had some surging earlier in the year. This corrected the problem
     
  17. West32

    West32 Active Member

    114
    May 24, 2017
    Racine
    1999 Sea Ray 370 EC Hardtop
    Raymarine Axiom Pro system, AP, Radar, VHF, Fox Marine Engine Monitor
    Twin Mercruiser 454 Horizon 380 hp
    Thank you for the long reply. The builder did say that one of the intake manifold gaskets did not look good and there was Oil up in the plenum. This would cause the computer to add more fuel.. I will be talking to the builder tomorrow about replacing the seats. Also, we replaced the cam with a Mercruiser Stock OEM Thanks again.
     
  18. West32

    West32 Active Member

    114
    May 24, 2017
    Racine
    1999 Sea Ray 370 EC Hardtop
    Raymarine Axiom Pro system, AP, Radar, VHF, Fox Marine Engine Monitor
    Twin Mercruiser 454 Horizon 380 hp
    Update. So the builder did not put Stock rings on the pistons. He put "High Performance" rings on. What we've learned is the Rings Mercruiser puts on are special. They have a special coating on them.
    By not using the right rings, Oil was getting into the compression chamber and coating the intake valve between the intake and exhaust valves. The Oil was building up and turning to carbon (Charcoal) and holding the valves open. The valves were not burnt, Just coated. Once he cleaned valves and checked them all of them were fine. He Bought new rings from Merc ($1300) and installed them. $1300 for rings is Insane..I'll be installing the engine on Monday, but I won't be able to run it until next year..
     
  19. techmitch

    techmitch Well-Known Member GOLD Sponsor

    May 1, 2008
    Chesapeake Bay, Middle River/Frog Mortar Creek MD.
    1999 270 DA
    Twin 4.3s W/Alpa I Gen II's
    Late to the party here. In reading your first post I see that the cam was replaced. I was wondering what the builder determined to be the root cause of the failure "wiped out" and were the lifters also replaced at the time of the repair?
     
  20. West32

    West32 Active Member

    114
    May 24, 2017
    Racine
    1999 Sea Ray 370 EC Hardtop
    Raymarine Axiom Pro system, AP, Radar, VHF, Fox Marine Engine Monitor
    Twin Mercruiser 454 Horizon 380 hp
    He said the root cause of the cam failure was the needle bearings in the lifters failing and the roller not rolling on the cam.
    On the rebuild, the Cam and lifters were replaced along with bearings and rings. The bores were "Perfect"
     

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