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1978 90 HP Mercury

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peterd

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"My boat was running great.I w

"My boat was running great.I went on vacation,the last day it suddenly died. I was going about 25. I can start it but as soon as I put it in gear it dies.I checked.Compression,spark,fuel, rebuilt carbs, fuel pump, no problems with the tank ,Lower unit it fine. I think I may have a vacuum leak.
How would I find it."
 
"Peter, If you have cleaned th

"Peter, If you have cleaned the carbs, and have good spark, then it is likely the carb idle mixture adjustments are set too lean. Open the top carb 1/8 turn and try it. If nogo, open middle carb 1/8 turn and try it if still nogo, open bottom carb 1/8 turn an try once more. Repeat if necessary. You want a rich enough setting to allow the motor to accelerate, but still idle reasonably well."
 
"When I move my throttle fwd i

"When I move my throttle fwd it gets to about 2000
rpm, then it starts to cut out and die if I continue to move it fwd. If I return it to idle it continues to run, This happens when it is in the water, it runs perfect in the driveway.I have checked fuel, fuel pump( new diaphram)new primer ball, rebuilt carbs. Checked Lwr unit, new plugs & wires, I have a very good spark at the coil when I jump the switch box. At the plugs ,the spark is blue but very narrow and it seems a little weak compared to what I see at the
coil.I suspect a problem with the trigger how can I check the trigger. Thanks"
 
"Peter, Here is the Distribut

"Peter, Here is the Distributor-based ignition test from Clams Canino, who is an inline expert.

MERCURY BATTERY-POWERED CDI TEST
FOR DISTRIBUTOR MODELS

This test is for the 332-2986 switchbox used from 1967-1978 on all the inlines.

This test assumes your coil is good (most all are).

DISCONNCT BATTERY

1. Turn off ignion
2. Disconnect all 3 wires on the distributor side of the switchbox.
3. Remove the HV lead from the coil to the center cap (remember it unscrews
from cap)
4. Reconnect that HV center lead to the COIL side only.
5. Position that HV lead about about 3/8" from ground (block, shrouds etc)
and find a way to hold it there.
6. Jumber the brown and white terminals on the dist. side of the switchbox
together.

RECONNECT BATTERRY

7. Check that you have +12 V at red terminal.
8. Turn on ignition and verify +12V at white terminal (on red terminal side)
9. Touch the black terminal to ground - unit should cause spark each time
you touch ground.

If that passes and it won't fire at all, suspect the trigger"
 
"I have tried that test severa

"I have tried that test several times. the spark
jumps a spark plug gap tester,a easy 1/2" I tried everything you mentioned plus more.
I have fuel and I have good spark. Runs great in the drive way but back it in the water put it
in gear, it will to about 1000 rpm. after it dies.How do I ck for Vacuum leak or reed problems. Thanks Peter"
 
"Peter, If the motor idles OK,

"Peter, If the motor idles OK, the reeds are likely good. It is also not likely you have a vacuum leak, if it idles well. I will presume the distributor rotates to advance the spark timing, as you push the throttle open. Do all three carb throttle plates open as well? Sometimes they rust shut. Are the plugs "steam-cleaned"? Id so, you may have water ingestion in the cylinders. Have you run a compression check? All cylinders should b within 10% of each other, and be 100PSI or better."
 
"Chris I brought my boat to a

"Chris I brought my boat to a boat shop where
this guys supposed to very good with these motors. He checked compression 149 to 154, has great spark, timing off 1 cog, fixed that. He adjusted fuel air mixture. Seem to run good.
I took it to the lake (Boat Ramp)Started fine, went to put it in gear same thing dies as I try to accelerate. I could get it to eccelerate if I pushed the choke button at the same time.
He seems to think its the carbs or internal problem. he doesn't think it's leaking water."
 
Did he check to see if the ble

Did he check to see if the bleed restrictors are in place. If he is knowledgeable he should have checked them
 
They are found when you remove

They are found when you remove the bypass covers. Your mechanic should know this.They are itty -bitty nylon bits and are usually missing.You need to check it out.
 
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