Hello, I'm trying to help a friend fix his 1976 Evinrude 70hp three cylinder outboard model # 70673D.
The boat is a 16" Fiberglas Tri-hull rated for 90hp max
It has a 13 1/4 X 17 prop on it now.
The engine was installed this year and we are using the prop that came with the engine. When the engine was installed we checked compression, the readings were 150, 143, 142. And the spark jumped 7/16" nicely but it wouldn't stay running unless I feathered the choke. So, removed the carbs and rebuilt them. I found plenty of gum & brown material. I rebuilt with new gaskets and made sure the floats were set correctly. Then I did a sync & link and used the Joe reeves method to check wot timing which was dead on. It ran great on the hose, but wouldn't rev up in gear in the water.
The tach didn't work either, I changed the rectifier and now it works fine.
The stator wiring looked questionable so I installed a new cdi stator..... Then it would get on plane but was slow revving from 3-4K rpm (10seconds+)
I changed two coils because they had cracks in them, but that didn't make any difference
I found a new CDI power pack for $80 so I tried that-- no difference
I removed the carbs and double checked float heights and removed and re-inspected all jets... Everything looked great and was very clean.
I put the carbs back on and it made no difference.
Then I checked a few more things:
1. Compression: 150, 144, 143
2. Spark jumps 7/16"... Tried running the boat with a timing light on each cylinder at all rpm. Never lost spark on any cylinder!
3. Had a friend drive the boat while it was revving slowly and tried spraying mixed fuel into each carb. Each time engine bogged down
4. Tried pumping the primer bulb while the engine was revving.... No difference
5. Pushed key in for choke while revving slow... No difference
The engine starts easily, idles smoothly, and will get up to 5500 rpm and run very nicely once it gets up to speed. Just takes forever to get up to speed.
If I have two people in the boat it will take 30 seconds to 1 min to get from 3k-4k rpm them will plane and rev smoothly.
More than two people in the boat and it will never get over 3k rpm!
So.... Other than slowly revving up the boat runs great. I can't seem to find anything else wrong with the engine and the bottom of the boat is clean, no algae.
Is this still an engine problem or is it propped incorrectly?
The boat is a 16" Fiberglas Tri-hull rated for 90hp max
It has a 13 1/4 X 17 prop on it now.
The engine was installed this year and we are using the prop that came with the engine. When the engine was installed we checked compression, the readings were 150, 143, 142. And the spark jumped 7/16" nicely but it wouldn't stay running unless I feathered the choke. So, removed the carbs and rebuilt them. I found plenty of gum & brown material. I rebuilt with new gaskets and made sure the floats were set correctly. Then I did a sync & link and used the Joe reeves method to check wot timing which was dead on. It ran great on the hose, but wouldn't rev up in gear in the water.
The tach didn't work either, I changed the rectifier and now it works fine.
The stator wiring looked questionable so I installed a new cdi stator..... Then it would get on plane but was slow revving from 3-4K rpm (10seconds+)
I changed two coils because they had cracks in them, but that didn't make any difference
I found a new CDI power pack for $80 so I tried that-- no difference
I removed the carbs and double checked float heights and removed and re-inspected all jets... Everything looked great and was very clean.
I put the carbs back on and it made no difference.
Then I checked a few more things:
1. Compression: 150, 144, 143
2. Spark jumps 7/16"... Tried running the boat with a timing light on each cylinder at all rpm. Never lost spark on any cylinder!
3. Had a friend drive the boat while it was revving slowly and tried spraying mixed fuel into each carb. Each time engine bogged down
4. Tried pumping the primer bulb while the engine was revving.... No difference
5. Pushed key in for choke while revving slow... No difference
The engine starts easily, idles smoothly, and will get up to 5500 rpm and run very nicely once it gets up to speed. Just takes forever to get up to speed.
If I have two people in the boat it will take 30 seconds to 1 min to get from 3k-4k rpm them will plane and rev smoothly.
More than two people in the boat and it will never get over 3k rpm!
So.... Other than slowly revving up the boat runs great. I can't seem to find anything else wrong with the engine and the bottom of the boat is clean, no algae.
Is this still an engine problem or is it propped incorrectly?
