1989 4.3 V6 RPM's falling off

[GA_Boater]

A crescent wrench and vice grips?

Metric bolts and Bottom Feeder Extraordinaire. LOL

I just hope it's the fuel pump after all!

 

[jasoutside]

Those were there just in case I decided to start smashing/crushing stuff.

All right, I see UPS has made his delivery, now I need to get home and bolt it on!

 

[jasoutside]

Well for crying out loud, no gasket in the box, rats! Yes the gasket was in the description and in the photo. Shoot.

 

[Rick Stephens]

Well for crying out loud, no gasket in the box, rats! Yes the gasket was in the description and in the photo. Shoot.

Any auto parts store.

 

[jasoutside]

Yah, just got back from town, everything is bolted on and ready for a driveway trial.

Just remember to turn on the water!!

 

[jasoutside]

Ran great in the drive......headed to the lake.....

 

[NHGuy]

never mind

 

[Watermann]

Ran great in the drive......headed to the lake.....

Oh man... standing by ray2:

 

[jasoutside]

Nope. Fail. Crap.

 

[thumpar]

Bummer. Have you gone through all your wiring connections and cleaned them up?

 

[jasoutside]

Bummer. Have you gone through all your wiring connections and cleaned them up?

Yah, pretty sure I had my hands on everything. Pretty much all new stuff really.

 

[jasoutside]

All right check it out. Round about 1:53 she starts dropping off. At 2:15 I throttle down.

So, not the fuel, fuel tanks, fuel lines, fuel filter, fuel pump. The carb is brand new but the marine techs checked that out (actually broke it down and rebuilt it) so that is good. Timing was also checked to be good.

 

[jasoutside]

Check this video out. I'm pretty sure I hear a knock of some sort at :12. It's kinda hard to hear in the video. I thought I heard it last night and then again here tonight.

I hate to say it but I stopped by the auto parts store on the way home and pick up a compression tester. I'm not interested in any more bad news today so I'll run the test tomorrow.

 

[jasoutside]

One other thing I should mention.....after those two videos I ran between 3800 and 4000 RPM for about 30 - 40 minutes no problem at all.

So confused.

 

[NHGuy]

By all means check the compression. I had an idea too.
Jas this is a stretch, but we are into WTH territory here. If your boat has normal Chevy lifters that are adjusted 1 turn from zero lash you MAY, not guarantee but MAY be getting lifter pump up.
You can work around it by spending money on higher end lifters. Or you can readjust the ones you have to 1/2 turn past zero lash.
If you are actually experiencing lifter pump up it will cause your valves to stay off their seats and thereby slow down your engine. It will go away as soon as the engine returns to lower rpms.
I don't remember, were there times the engine continued to act badly or was it just for a short time at WOT?

 

[NHGuy]

If you have spark knock it may show in your spar plugs. Which engine & ignition is yours based from? Thunderbolt IV? TB V?

 

[Rick Stephens]

By all means check the compression. I had an idea too.
Jas this is a stretch, but we are into WTH territory here. If your boat has normal Chevy lifters that are adjusted 1 turn from zero lash you MAY, not guarantee but MAY be getting lifter pump up.
You can work around it by spending money on higher end lifters. Or you can readjust the ones you have to 1/2 turn past zero lash.
If you are actually experiencing lifter pump up it will cause your valves to stay off their seats and thereby slow down your engine. It will go away as soon as the engine returns to lower rpms.
I don't remember, were there times the engine continued to act badly or was it just for a short time at WOT?

That's a good idea - valve problems would be easy to see on a vacuum gauge, wouldn't it?

 

[NHGuy]

Not really in this scenario, it only happens at very high rpm.

 

[Patfromny]

Completely out of left field but do you have power steering? You might be pumping the reservoir dry and loading up the motor? Or it is binding when warmed up. It is weird that this seems to be happening within 15 seconds of each other on each run. Thinking electrical but it is too regular an event. Like something is bogging down the motor just before the 2 minute mark.. Or something takes just less then 2 minutes to warm up and fall. Maybe disconnect the power steering pump for a run. Sorry but I'm not sure if you have one or if you can do this without hurting some other marine part. Or if it is on a serpentine belt. I'm just a car and outboard guy so I'm not at all familiar with what is belt or gear driven on your setup. I'm starting to think that is something actually bogging down the motor and not the motor stumbling. The engine sounded ok the last couple of tests but just seemed to be loaded and unloaded. Maybe someone with io knowledge can advise what you can safely disconnect alternator, power steering pump, things like that. A/C compressor? LOL. Sorry, for my lack of knowledge. You could hold a hose or screw driver to the pump and the other end to your ear and listen for any bearing noise. Just coming out of left field hear but something to look at. The last two passes sounded like the prop was being dunked in and out of mud or jello.

 

[Baylinerchuck]

Very good troubleshooting tips here, enjoying the read....sorry it's at the expense of your boat not running well. Fingers crossed you find the problem soon.