4.3 loses power, ticks after long WOT runs

[CatriderF7]

I have a 1987 Rinker that we replaced the motor with an engine out of a 93 Blazer. Took it out last weekend and it runs great, idles fine, never dies or anything. Has lots of power, does 45mph with 2 people in it. at about 4500rpm. but when its ran for a few minutes at wide open throttle it starts to tick and loses power, if you let off for a minute and get back into it it runs fine, or if you stay at a lower throttle position and go in and out of full throttle it runs great. It gets up to about 175 degrees when the issue happens, and is at 165 most other times. Or if you stop for a minute from full throttle it drops to 165 and then it runs fine. Anyone know what this might be? seems to me like an overheating issue.. but 175 is far from overheating.

 

[Bondo]

Re: 4.3 loses power, ticks after long WOT runs

I have a 1987 Rinker that we replaced the motor with an engine out of a 93 Blazer. Took it out last weekend and it runs great, idles fine, never dies or anything. Has lots of power, does 45mph with 2 people in it. at about 4500rpm. but when its ran for a few minutes at wide open throttle it starts to tick and loses power, if you let off for a minute and get back into it it runs fine, or if you stay at a lower throttle position and go in and out of full throttle it runs great. It gets up to about 175 degrees when the issue happens, and is at 165 most other times. Or if you stop for a minute from full throttle it drops to 165 and then it runs fine. Anyone know what this might be? seems to me like an overheating issue.. but 175 is far from overheating.

Ayuh,... It's probably detonation, due to a lean condition... Check the contents of the fuel filter...

 

[CatriderF7]

Re: 4.3 loses power, ticks after long WOT runs

It actually has a brand new filter and electric pump on it. And now I have a new problem. I went to take it out yesterday and it started up and idled fine, and I went to take off and it has a bad hesitation and almost a knock sound to it. If I put it in neutral it'll rev up fine, but in gear under load it will not go. It feels like 2 spark plugs are disconnected. But everythings hooked up fine and nothing was changed or messed with since the last time I took it out and it ran fine. I'm thinking maybe change the plugs and wires, just seems weird they'd just go bad over the week of not being used.

 

[Howard Sterndrive]

Re: 4.3 loses power, ticks after long WOT runs

might want to check the lube in the outdrive

 

[Don S]

Re: 4.3 loses power, ticks after long WOT runs

Check the engine oil level. If it's over full, the crankshaft will hit the oil and aerate it. The oil then won't let the lifters pump up, they make noise and you loose power.

 

[CatriderF7]

Re: 4.3 loses power, ticks after long WOT runs

Well I checked fluids and whatnot and everything seemed fine. Then i decided to check compression, all cylinders were over 150psi until i got to the #4 and #6 cylinders and they had 30psi on them. so i assumed there was a stuck valve or something. Pulled the head off and the head gasket was blown between the 2 cylinders, there was a good half inch long piece missing, and i could tell by looking at the block and the head that it had been missing for a while because i could see the impression of the gasket on both pretty clearly. Got a new gasket in it tonight and did a compression check and got the compression back on the #4 and #6 cylinders. Going to get the valves adjusted in the morning and hopefully get it started up and see how it runs

 

[CatriderF7]

Re: 4.3 loses power, ticks after long WOT runs

 

[Howard Sterndrive]

Re: 4.3 loses power, ticks after long WOT runs

unless you saw some obvious root cause (like loose head bolts or warped head) , you might want to check exhaust shutters, and riser to manifold surfaces/gaskets on that side while you have that apart. That missing chunk of head gasket may have resulted from a hydrolock.

 

[CatriderF7]

Re: 4.3 loses power, ticks after long WOT runs

Well I think the head gasket was partially blown when i bought the motor. Because when i first ran it it ran great but had a slight tick that i was thinking was maybe a loose manifold bolt, i tightened all the bolts and it kept up, but it was quiet enough to where you had to be listening to it with the engine cover off to hear. Then it just all of a sudden went out last weekend when i tried to take it for a drive, so im thinking it was on its way out when I bought the motor.

I got it out on the water today and it runs great again but it is still ticking, alot lighter than it was before tho, im hoping its the valves. can anyone tell me the torque procedure for the valves on these? the manual i have only shows for the heads with positive stop studs. Mine are the studs that are pressed into the head. and should the timing be set to 0 on the harmonic balancer?

 

[Howard Sterndrive]

Re: 4.3 loses power, ticks after long WOT runs

im thinking it was on its way out when I bought the motor.

the head gasket isn't a wear item. They are never "on their way out"
something else always causes a head gasket to fail.
In your case, I would suspect you have water ingression to at least one of the cylinders either side of that breech, and probably that side of the engine in general indicating a faulty shutter, riser gasket or manifold etc. or maybe the engine was overheated at one time and the head or block is warped.

can anyone tell me the torque procedure for the valves on these? the manual i have only shows for the heads with positive stop studs. Mine are the studs that are pressed into the head.

you should get the correct manual for your model, but the best way to be 100% sure on valve adjustment is to use a compression tester and a remote crank switch.
With the valve covers off, ignition disabled, crank the motor, watch compression - tighten each valve until compression drops off, then keep cranking and loosen it until the rocker is loose.
Split the difference and you know you are dead center of the nut's adjustment range.
double check compression then move to the next cyl and repeat.

 

[Lou C]

Re: 4.3 loses power, ticks after long WOT runs

Ticking, do you mean spark knock or the sound bad valve lifters make? Because if you have multi-vis auto engine oil in that engine, and you run it wide open for any length of time, the oil could be breaking down and that might cause the lifters to not function properly, causing the noise and reduced performance. How is your hot idle oil pressure when this happens? If you have a multi vis oil in there now try changing it to a straight 30 or 40.

 

[CatriderF7]

Re: 4.3 loses power, ticks after long WOT runs

the head gasket isn't a wear item. They are never "on their way out"
something else always causes a head gasket to fail.
In your case, I would suspect you have water ingression to at least one of the cylinders either side of that breech, and probably that side of the engine in general indicating a faulty shutter, riser gasket or manifold etc. or maybe the engine was overheated at one time and the head or block is warped.


you should get the correct manual for your model, but the best way to be 100% sure on valve adjustment is to use a compression tester and a remote crank switch.
With the valve covers off, ignition disabled, crank the motor, watch compression - tighten each valve until compression drops off, then keep cranking and loosen it until the rocker is loose.
Split the difference and you know you are dead center of the nut's adjustment range.
double check compression then move to the next cyl and repeat.

Thanks. something may have caused it, but at the same time people have head gaskets and intake gaskets go out everyday and have just the gasket replaced, the head would only be warped if it overheated. What i meant was i think it was already blown to some extent and the running i did with it blew it out more. But it has good compression now and ive ran it a couple times without any problem in running, has plenty of power and gets on plane quick. just has a ticking sound, and only under load not while its in neutral. I have set the timing to 2 degrees BTDC and the noise did get quieter, but is still there.

Im going to try to get the valves set tonight and take it out in the morning with someone else so i can sit by the motor and try to determine where the noise is coming from. I may change the oil too. ill see what the pressure is at at idle tomorrow morning

 

[Howard Sterndrive]

Re: 4.3 loses power, ticks after long WOT runs

people have head gaskets and intake gaskets go out everyday and have just the gasket replaced,

the head gasket is never the root cause of a head gasket failure. especially on a boat like yours with a non-pressurized cooling system. and when you see a big chunk excavated out, including the fire rings like in your picture. Of course, in a Blazer, the cooling system is pressurized, but still not the gasket that caused the failure initially - but yeah, it may have been half gone in the Blazer.

Water can do that, ether starting fluid can do that, detonation can do that, warped parts can do that.

Did you notice the valves in that center cylinder are a touch rusty compared to the others? That rust probably happened as a result of the breech in the gasket, but it might be pointing to a cause too.

All that said - a new gasket, especially a composite one like Fel-pro with a lot of "squish" can compensate for warped parts and you might be ok.

ticking sound, and only under load not while its in neutral. I have set the timing to 2 degrees BTDC and the noise did get quieter, but is still there.

what is the timing spec?
That sounds like detonation due to improper timing. You might want to verify the timing again and check the advance.

Do you maybe have a mismatch of marine dampener/pulley with Blazer timing tab?

You have a marine distributor? not the peripherals out of the Blazer.

 

[Lou C]

Re: 4.3 loses power, ticks after long WOT runs

There's definitely water in the cylinder in your pix....I'd for sure change the oil when you have it back together and use a straight 30 or 40...

 

[CatriderF7]

Re: 4.3 loses power, ticks after long WOT runs

Well Ive checked the oil a few times and theres no water showing on the dipstick, or the oil on the heads either. But I am going to go to a straight weight oil, thanks for the suggestion.

Im not sure on the cause of the gasket failure, but we'll see if just changing the gasket holds up.

Im not sure what the timing spec is, thats something i havent been able to find. Everything ive seen is all different numbers. Im going to play with it some more tomorrow and see what i can do with the timing. I took the pulley and timing chain cover off the marine motor, and the distributor is off the marine motor too.

 

[Howard Sterndrive]

Re: 4.3 loses power, ticks after long WOT runs

8 deg btdc was the Mercruiser spec,
which is why I question the marks, because it wouldn't go 45mph at 2 deg. especially with a failing head gasket. and detonation is the result of timing too far advanced usually.

You could always get or make a timing tool to see where the marks say you are when #1 piston is at TDC.

 

[CatriderF7]

Re: 4.3 loses power, ticks after long WOT runs

well that speed was before. The timing was at like 14 degrees BTDC when i was getting that speed. I originally set the timing by ear just to get it to idle and then took it out to see if it would run and it did, so i left it. I only realized it was way off yesterday when I bought a timing light, then i set it to 2 degrees. It still runs great, I honestly dont think its any slower. But I was thinking the same thing becuase in order for it to have a smooth idle it had to be off the gauge BTDC, so i watched in the #1 plug hole and crank the motor over with a wrench til the piston was at TDC and sure enough the line was right at 0 on the balancer

 

[CatriderF7]

Re: 4.3 loses power, ticks after long WOT runs

The oil pressure at idle is about 20-25psi