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This is a very long post, i have tried to be as detailed as possible. PLEASE read it and give me your opinion….Please
I recently purchased a 2000 key largo with a 2000 90hp Johnson Ocean Pro on it. (with VRO)
The seller was upfront with me that at low idle (when throttling down) sometimes it would die, but it would always fire right back up. I sea trailed the boat and it did exactly as the seller described. After, I had a reputable mechanic come check out the motor before I actually purchased it. The mechanic did a compression test and all 4 cylinders were over 100psi and all even. he found no other problems, but he could not repeat the dying at idle on muffs (as it only did it on the water). He said it was probably a warped float bowl chamber and would be a fairly easy fix.
I feel like he is a good mechanic, been doing this for 30 years, familiar with this motor, and he is not just a parts changer.
Well, it turns out that a few of the float bowls were warped, but not causing the issue. he found out that On number 4 cylinder the spark plug was getting wet with water, which is why he thought it was dying and not sucking the fuel properly. He tore about all 4 carbs and adjusted float bowls and found nothing wrong. So then he pulled off the heads and noticed that the head gasket o rings were not in good shape, there was some rtv sealant plugging some of the water openings, and the heads were not in great shape. So he thought that water was leaking from the water jackets (i think thats what they are called under the heads) so he had the heads machined so they were in good shape and nice and flat again. then he put new head gasket o rings on and it was a little better, but cylinder 4 was still not pulling fuel at low idle and the plug in that cylinder was still wet with water. all 3 cylinders, except number 4, actually picked up about 10 psi of compression after doing the heads. number 4 had stayed about the same. So now he thought the rings on the piston in cylinder 4 were stuck which was causing cylinder 4 not to pull enough fuel at idle, but also let a little moisture from the exhaust port, inside the cylinder, be pulled into the intake port which was causing the wet plug. So he did some ring free and let it soak. Well that freed up the ring and now that cylinder has the same compression as the other cylinders, but the plug in that cylinder 4 is still wet causing it to die at idle. He said when he manually chokes cal 4 it picks up as it is pulling more fuel and the spark plug start firing again……
so, that is where we are at now. He has fully checked out the VRO, fuel and oil are both 100% free from water, and carbs are 100% he says. he said there are only 2 other places that water could be coming into cylinder 4 causing the plug to get wet which is causing it to die at low idle. He said 1 place could be block rot, but be is 99% sure this is not the case as he has found no evidence of it and he says that these motors were not at all prone to it. The only other place he thinks water may be coming in is from the lower main seal. I think he said that is near the crank….
I think he is a very good mechanic, not just a parts changer, and he really wants to fix this as we are both frustrated at this because it seemed like a simple problem at first and now we are about to tear down the motor to get to the lower main seal as that is where he thinks the water is coming in, causing the plug to get wet, and causing 4 cylinder to die at low idle….
does this sound like we are on the right track? we both think we have tried the simple, cheapest things first, now we are left with this lower main seal….Can someone chime in and let me know if you think we are on the right track? Any suggestions?
EDIT:
Edit: just spoke to the mech, and to clarify about the lower main seal he said:
The power head base gasket is the mounting surface and the lower main is the sealing surface between the bottom cylinder and the water in the exhaust. the base gasket and the lower main seal are the two that will be replaced, you cant pull the power head and reinstall without a new base gasket you can however pull the power head and reinstall without replacing the lower main seal. we will of course be replacing them both
I recently purchased a 2000 key largo with a 2000 90hp Johnson Ocean Pro on it. (with VRO)
The seller was upfront with me that at low idle (when throttling down) sometimes it would die, but it would always fire right back up. I sea trailed the boat and it did exactly as the seller described. After, I had a reputable mechanic come check out the motor before I actually purchased it. The mechanic did a compression test and all 4 cylinders were over 100psi and all even. he found no other problems, but he could not repeat the dying at idle on muffs (as it only did it on the water). He said it was probably a warped float bowl chamber and would be a fairly easy fix.
I feel like he is a good mechanic, been doing this for 30 years, familiar with this motor, and he is not just a parts changer.
Well, it turns out that a few of the float bowls were warped, but not causing the issue. he found out that On number 4 cylinder the spark plug was getting wet with water, which is why he thought it was dying and not sucking the fuel properly. He tore about all 4 carbs and adjusted float bowls and found nothing wrong. So then he pulled off the heads and noticed that the head gasket o rings were not in good shape, there was some rtv sealant plugging some of the water openings, and the heads were not in great shape. So he thought that water was leaking from the water jackets (i think thats what they are called under the heads) so he had the heads machined so they were in good shape and nice and flat again. then he put new head gasket o rings on and it was a little better, but cylinder 4 was still not pulling fuel at low idle and the plug in that cylinder was still wet with water. all 3 cylinders, except number 4, actually picked up about 10 psi of compression after doing the heads. number 4 had stayed about the same. So now he thought the rings on the piston in cylinder 4 were stuck which was causing cylinder 4 not to pull enough fuel at idle, but also let a little moisture from the exhaust port, inside the cylinder, be pulled into the intake port which was causing the wet plug. So he did some ring free and let it soak. Well that freed up the ring and now that cylinder has the same compression as the other cylinders, but the plug in that cylinder 4 is still wet causing it to die at idle. He said when he manually chokes cal 4 it picks up as it is pulling more fuel and the spark plug start firing again……
so, that is where we are at now. He has fully checked out the VRO, fuel and oil are both 100% free from water, and carbs are 100% he says. he said there are only 2 other places that water could be coming into cylinder 4 causing the plug to get wet which is causing it to die at low idle. He said 1 place could be block rot, but be is 99% sure this is not the case as he has found no evidence of it and he says that these motors were not at all prone to it. The only other place he thinks water may be coming in is from the lower main seal. I think he said that is near the crank….
I think he is a very good mechanic, not just a parts changer, and he really wants to fix this as we are both frustrated at this because it seemed like a simple problem at first and now we are about to tear down the motor to get to the lower main seal as that is where he thinks the water is coming in, causing the plug to get wet, and causing 4 cylinder to die at low idle….
does this sound like we are on the right track? we both think we have tried the simple, cheapest things first, now we are left with this lower main seal….Can someone chime in and let me know if you think we are on the right track? Any suggestions?
EDIT:
Edit: just spoke to the mech, and to clarify about the lower main seal he said:
The power head base gasket is the mounting surface and the lower main is the sealing surface between the bottom cylinder and the water in the exhaust. the base gasket and the lower main seal are the two that will be replaced, you cant pull the power head and reinstall without a new base gasket you can however pull the power head and reinstall without replacing the lower main seal. we will of course be replacing them both
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