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Johnson 70pk 1992

N

nigelsalari

New member
Hey me and my friend bought an project boat togheter we got the engine running and testen the boat for leaks.
When we got it in the water its very slow for an 70 we hit max 20 kmh, the enige seems to run fine and doesnt stutter however I dont think its hitting the 5k rpm like jt should but I could be wrong. Does somebody think they know the problem or have any thing we have to test?
We change the propeller for an New one Spoed 17 [13 1/4 x 17].

Video's if the engine


Screenshot_20230602_181354.jpg
 
Start with a compression test.----Post your numbers.----Then check spark.----Spark must be able to jump a gap of 9 cm with ease on a test device.----Sounds like it has a dead cylinder and running on 2 of 3 cylinders.
 
They sell those spark testers at most chain automotive stores. I'd look online for step-by-step procedure for synching carburetors and setting up timing also. I can't tell from the pictures, but is the motor sitting at the correct depth. On that boat, there might be too much of the motor in the water causing a terrible drag. As mentioned above, a dead cylinder will run fine when hooked up to a hose, but will reduce performance and top end drastically when under a load.
 
racerone said:
Start with a compression test.----Post your numbers.----Then check spark.----Spark must be able to jump a gap of 9 cm with ease on a test device.----Sounds like it has a dead cylinder and running on 2 of 3 cylinders.
Click to expand...
I have ordered an compression test and spark plug tester. And I'm gonna test them.
 
racerone said:
Start with a compression test.----Post your numbers.----Then check spark.----Spark must be able to jump a gap of 9 cm with ease on a test device.----Sounds like it has a dead cylinder and running on 2 of 3 cylinders.
Click to expand...
I have ordered an compression test and spark plug tester
 
Oldsaltydog said:
They sell those spark testers at most chain automotive stores. I'd look online for step-by-step procedure for synching carburetors and setting up timing also. I can't tell from the pictures, but is the motor sitting at the correct depth. On that boat, there might be too much of the motor in the water causing a terrible drag. As mentioned above, a dead cylinder will run fine when hooked up to a hose, but will reduce performance and top end drastically when under a it
Click to expand...

I think the motor is at the wrong depth its not meant to be on this size boat the motor is way to big
 
Have you cleaned the carbs?

Have you changed any fuel hoses or just ran what was on?

Iv got a 70 (in bits at the mo) on a 4.5m boat and it flys..
 
Nick0151 said:
Have you cleaned the carbs?

Have you changed any fuel hoses or just ran what was on?

Iv got a 70 (in bits at the mo) on a 4.5m boat and it flys..
Click to expand...
I haven't clean clean the carb the motor doesn't stutter or act weird out the water it does sound like it higher in rpm
 
I’d clean the high speed jet at the bottom of the float bowl or at least check it as with no load would rev ok. One blocked will stop it working can get little cleaning set for less then fiver one Amazon..
 
They all sound great running on a hose.----Will sound great running on 2 of 3 cylinders !-----Not a good way to judge the health of a motor.
 
It is the correct length for the boat.----Some trouble shooting has to be done.----Hard to do this for you from 5000 miles away.
 
racerone said:
It is the correct length for the boat.----Some trouble shooting has to be done.----Hard to do this for you from 5000 miles away.
Click to expand...
I dont have any knowledge about boat's so if you can help me would be amazing. This weekend I'm gonna clean the carb,s and do an compression test wil post results
 
racerone said:
Start with a compression test.----Post your numbers.----Then check spark.----Spark must be able to jump a gap of 9 cm with ease on a test device.----Sounds like it has a dead cylinder and running on 2 of 3 cylinders.
Click to expand...
I did an compression test and they al 3 have spark and 10 bar of compression wil now clean the carb
 
Did you run the outboard with no water for the impeller? If so may have burned it up.

Are the any blockages in the pee tube?
 
Nick0151 said:
Did you run the outboard with no water for the impeller? If so may have burned it up.

Are the any blockages in the pee tube
Click to expand...
The was an blockages I blowed some wather true the pipe and now is works again.
Yesterday we did an test run and the enigene is running great we hit 50km/h. Can I get more out of this enigene? Wil post video of the test run
 
On the prop does it say what pitch it is guess using 15p if the are any marking on it be good to find out.

May be able to use 19p

Do you have a tachometer on there to know what the rpms are when WOT
 
Nick0151 said:
On the prop does it say what pitch it is guess using 15p if the are any marking on it be good to find out.

May be able to use 19p

Do you have a tachometer on there to know what the rpms are when WOT
Click to expand...
Here is the video of the engine running in the water now

We bought an New one we got the 13-1/4x17
Was the same as the old one
 
Does the engine have electric trim and tilt? If not the bar move it up one as should be getting a few mph more than you are test see how it rides may need to move it back
 
No it doesn't have an electric trim we changed the bar a couple times and we got the best results with this height.
When testing we didn't realy go any faster it was more or less bouncy. It 30 mph rewly the Max of this boat and engine?
1 Other thing changing gear doesn't realy work you cant go backwards if you push the rod bij hand it work but but if you use the command center it doesn't push far enough.
 
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