454 wont go over 32-3400 rpms

Im still working on recovering and repairing all the troubles I had during my vacation trip. I had a bad U-joint and I replaced both of them now, along with the gimbal bearing and bellow. I swapped my B1 lower that was cracking for a B3. The other problem I had was that I would come up on plane and get to 3400 RPMs and it wouldnt do anymore. I pushed the throttle all the way down and nothing changed. It was running smooth and had no hesitation at all. It runs perfect from idle to 3400. I dropped off plane changed both the inline fuel filter and the water seperator filter. No change. It just wouldn't go any faster. I usually run up to 36-3800 to get around boats and such and top out around 4300. I checked today and made sure the throttle cable was opening the butterflies wide open and it was. I checked the secondaries and it seemed to work smoothly by hand. I did notice a large amount of black on the flame arrestor from the crankcase breathing. I cleaned that to new condition. Would this being clogged cause the problem I described? Bad u joint cause it? Any other suggestions? Its not running out of fuel, it just wont open up! Im just trying to get everything back in order for the winter!

Re: 454 wont go over 32-3400 rpms

Older 454 ????

Check the compression . . . then . . . do a cylinder leak test . . . . followed by a cooling system pressure test.

Weak point is the cylinder heads.

Re: 454 wont go over 32-3400 rpms

I don't know much about bravos but could the ratio be wrong with lower switch to a B3 from a B1. That would easily explain the change. I know on an alpha the ratio is in the upper don't know on the bravo.

Re: 454 wont go over 32-3400 rpms

I will do a compression check tomorrow and a leak down. I haven't run it with the B3 yet. It is raw water cooled so I have no way to check cooling. It is a Gen IV but it was rebuilt a couple years ago.

Re: 454 wont go over 32-3400 rpms

Props & gear ratio!

Re: 454 wont go over 32-3400 rpms

None of the drive/prop stuff was changed before the proplem. Everything happened at the same time. I am fixing it all now. The B3 and the new props havent seen the water yet.

Re: 454 wont go over 32-3400 rpms

Describe your 454. Year? Carbed? EFI? Serial number? What gear ratio is your drive now?

Sounds like you may have the wrong ratio, but you could also have engine problems as well.

Timing, fuel system working OK? When was the last tunup including a compression check?

Re: 454 wont go over 32-3400 rpms

It is a 1995 454 which was rebuilt less than 100 hrs ago. It has nothing to do with the ratio because the drive was changed after the problem. I havent had the boat in the water with the new B3 installed. All the rpm issues was before the drive swap. Last tune up was August of last year, about 15-20hrs ago. New wires, plugs, cap, rotor. I didn't run a compression check for normal maint. but will run one tomorrow. It was running fine heading down the Atlantic from VA Beach to Oregan Inlet, NC and up to Manteo. I ran from Manteo to Hatteras and it started it then. The only other thing that comes to mind was I put 100 gallons of fuel in from Wanchese. Maybe the gas was crap? How can I determine that? It still has about 50 gallons in the tank. It runs fine with no load, I can rev it up all day on the trailer. I would suspect bad gas to cause popping and sputtering and missing.

Re: 454 wont go over 32-3400 rpms

I just had a similar issue, albeit on a smaller boat with a 4.3 V6. I threw off the timing when changing my cap and rotor. The boat would rev freely at idle and ran fine on the water up to 2000 RPM, at which point it simply wouldn't go any more. It's worth checking and will only take a few minutes of your time.

Re: 454 wont go over 32-3400 rpms

fastimz said:

.... The only other thing that comes to mind was I put 100 gallons of fuel in from Wanchese. Maybe the gas was crap? ...

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Sounds like a good bet. Was this fuel from a marina? If so, they have a nasty habit of having old/stale/low quality fuel. Take a sample and have it analyzed. I would get a couple of outboard tank and fill them with known good fuel and take it for a run... Just check compressions before you do to ensure no damage has been done to the engine.

Yep, with no load it would also run fine on kerosene... That's no test. Under normal load conditions is the only proper test.

Chris........

Re: 454 wont go over 32-3400 rpms

I will check the timing also the compression check. It is storming bad here today so it will be postponed on results. The fuel did come from a marina.

Re: 454 wont go over 32-3400 rpms

Alright, I went out in the crap weather and checked the timing and it was spot on. I ran a compression check which has me concerned now. Al 8 cylinders had 98-105 lbs. Im a race car guy and my cylinder pressure in that motor reads 190-200 lbs. It doesn't seem to point to any one or two cylinder as the problem. Plugs looked good, nice and brownish. Is this winter going to be rebuild time or will these compression numbers due? I will do a leak down on her tomorrow and try to pinpoint it from rings or heads.

Re: 454 wont go over 32-3400 rpms

fastimz said:

.... It is a Gen IV but it was rebuilt a couple years ago.

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fastimz said:

It is a 1995 454 which was rebuilt less than 100 hrs ago. ....

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Doesn't fit. Mark IV blocks finished in 1992. Need a serial number...

fastimz said:

All 8 cylinders had 98-105 lbs. ....

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That's not good, my book genuine Merc) says 150-160psi. Check your gauge on a known good engine.

Chris.......

Re: 454 wont go over 32-3400 rpms

achris said:

Doesn't fit. Mark IV blocks finished in 1992. Need a serial number...



That's not good, my book genuine Merc) says 150-160psi. Check your gauge on a known good engine.

Chris.......

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I am really curious as to how this plays out. My 1993 454 (bayliner 2859 super classic) overheated at the start of summer and has not run right since. Used to jump on plane and run over 4200 rpm about 32 mph. Now it struggles to plane out and won't go over 3700 rpm (24 mph). If I run it at that, it starts to slowly over heat. Changed water pump, plugs, wires, cap rotor, checked timing-nothing.

I need to do a compression test as well but if anyone has any other ideas i am all ears.

Re: 454 wont go over 32-3400 rpms

Welcome to iboats markoet, read the archives for information, and do a compression test on your engine, but do start a new thread of your own for further information. It gets really confusing when 2 people have problems in the same thread. That's why we have that big red "Post New Tread" button.

Re: 454 wont go over 32-3400 rpms

I can say this about my '95 7.4L, with timing set at standard 6degBTD (I think from memory) the engine is a bit sluggish out of the hole and won't rev quickly. So, I've advanced my timing just a bit by ear so it doesn't ping nor kick back on hot start up. It launches much quicker and rev's several hundred rpm's higher.