Johnson 88 SPL won't accelerate

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bs818

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Apr 25, 2015
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My Johnson 88 SPL outboard motor runs fine out of water (other than a low idle speed), but when I put in in the water, it won't accelerate. It's just stays at idle. The RPMs won't come up. All my cylinders are 120 after doing a compression check.

Not sure where to go from here. Any help on what the problem could be?
 
R

racerone

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Dec 28, 2013
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They all run well on a hose !----Most folks can not tell if the motor is running on 3 or 4 cylinders on a hose. All they hear is noise.------Check and see if there is spark on all 4 leads.---Good spark is spark that will jump a gap of 3/8" or more.---Possibly a plugged carburetor jet is the problem.--That is a serious problem.----If one carburetor jet is plugged than that cylinder will be starved of OIL as well.
 
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Fed

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Putting it in gear then trying to accelerate with the fast idle lever?
 
E

emdsapmgr

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Follow Racerone's suggestion. Check for spark on all 4 plugwires after the engine is well warmed up. A cyl drop test works well also.
 
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bs818

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Update: Thanks for the responses so far. I don't think that it is a stopped up jet because the spark plug is wet with fuel when I pull it out. Here is what I have done so far: I rechecked compression on all 4 and three are at 118 psi and 1 is at 120 psi. I swapped spark plugs around with no change. I pull the spark plug wire off of that cylinder and the motor doesn't change at all. No rpm change or anything. I also moved the spark plug wires around with no change. I have also swapped the coils around with no change. I checked the spark on the plug of the cylinder in question and it seems to have good fire. I would think if it were a plug, wire, coil or ignition module problem, that the problem would have moved with the things I did. The motor seems to be running better today (idling at low idle without cutting of or being rough) but it shows no change when I pull the wire off of the plug on that one cylinder. All others are very noticeable when I pull them off one at a time. Now I am scratching my head #$%! Could it possibly be that I have a valve on that cylinder that is slow reacting ( gummed up) that could be causing this? If so, would a good dose of sea foam possibly help? Thanks!!
 
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R

racerone

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If you have spark and compression that leaves fuel and crankcase compression as the posible issue.----Reed valves are very reliable on these V-4 motors.---That leaves the issue as a possible carburetor problem and that would be an easy fix.----Have you checked the flywheel key?
 
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emdsapmgr

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Dec 9, 2005
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Testing for spark while the engine is running by pulling the spark plug wire off the plug is the "cyl drop" test. Usually, if that cyl is firing and you pull the plugwire off, the engine's rpm's will drop. When you reconnect it, the rpm's should raise back to normal. If you pull the plugwire off and nothing happens, either you have no spark on that plug or that cyl is not getting any fuel. Problem with getting no fuel is that the cyl is also not getting any lubrication. You may need to pull the carb off that feeds that cyl and remove the jets on that throat for a visual inspection for any restriction...
 
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