Johnson 1975 70 hp seahorse outboard stalling while submerged

[Icemanana]

motor runs perfect with the water hose at home and put forward and reverse and the prop engages, however once I took it to the boat ramp and motor was submerged when put in gear shuts off. Carbs were recently rebuild. I went back home and again run it with the water hose starts right up and forward and reverse perfect any suggestions? Thanks in advance

 

[jbuote]

No expert, but I THINK if you set the idle in the driveway on muffs, then take it to the lake it'll die on shifting into gear... More back pressure on the exhaust in the lake, so you need a higher idle on muffs to get the proper lower idle on the lake...

​That's what I'm thinking anyway... I'm sure someone will either confirm or correct this though! LOL :joyous:

 

[clemsonfor]

Yea it can just be something as simple as the idle for the reason stated above.

 

[flyingscott]

The idle should be 1200 rpms on muffs about 750 in gear and warm on the lake. Do a compression and spark test.

 

[racerone]

It only " sounds good to you " running on the hose.----It will run good on 2 of 3 cylinders.-----Do the compression test and spark test as already stated !!

 

[Icemanana]

Ok thanks I will do the compression test and let you guys know.... thanks for the good advice

 

[Silvertip]

How about doing it this way: 1) Make sure the engine is running on all cylinders. If not fix it. 2) What does the tach read at idle? If low, fix it. 3) If #1 and #2 are ok THEN do the compression test. Of course if the engine is NOT running on all cylinders a compression test would be called for but do the obvious and cheap things first rather than the time consuming and expensive stuff that is wasteful.

 

[Icemanana]

I just got me a non contact Tach so I will be reading the RPM's and do the compression test =..I will let you know the outcome. Can I use the non contact Tach by pointing the flywheel to read the RPM's (I got one of those non contact tachmeneters with the reflective tape) ? Thanks in advance.

 

[Icemanana]

An update since no one responded I did put the reflective tape on the flywheel and it measure about 2500 rpm is that ok ? I will run the compression test this week thanks

 

[Icemanana]

2500 rpm were on the water hose in idle neutral

 

[racerone]

You have not responded with results of tests !------Winding the motor up on the hose proves nothing.----May in fact be bad for the motor.----In gear on the traler is in fact still nuetral because the prop does no " work " to push air.

 

[Icemanana]

Thanks I will post the compression test once completed, I also wanted to let you know that the carbs were recently re built

 

[Icemanana]

Compression and spark test completed. Spark perfect and the compression test was 110 and all 3 cylinders. I believe that the trotle cable needed to be adjusted so hopefully next time I put it on the water it will work.

 

[jimmbo]

Thanks I will post the compression test once completed, I also wanted to let you know that the carbs were recently re built

When you did the carb rebuild, did you do a linkage synchronization between the carbs and ignition?

 

[Bosunsmate]

2500rpm is still far too high out of the water, it should settle right back down.
Its possible your flywheel is out of timing or something else.
Move your flywheel so 0 aligns with the pointer on the engine and then check that your top cylinders piston is at TDC, top dead centre ie it is at its very end of its reach towards the sparkhole. If its not it means that your timing is out and hence why you have no power and such a high idle rpm

You should post a video if you a unsure, of it running at idle and a close up of your linkages

 

[Icemanana]

Sure I will, I tried but the site would not let me I might post it on you tube and provide you the link,. The carbs were rebuild on the boat shop and I believed that he did synchronized them.

 

[Bosunsmate]

Look at the colour of your sparkplugs too

 

[racerone]

Some will argue----My compression tester shows 140+ on these motors in good condition.-------------Head gasket is cheap

 

[Driftwood Jim]

Well I would do all my testing in a barrel or on the lake as stated above.
Carburetor sync:
1 -each carb needs to flow the same amount of air/fuel mixture at idle, set low speed idle screws the same amount out . Very important because if it is not equal at idle it will not be equal at speed=uneven amounts of fuel feeding the motor= uneven running. use an airflow gauge for this on each carb. do this with the linkage unhooked
2- the linkage needs to be sync'ed so the carbs open the same amount together so each cylinder is feed the same amount of fuel
I know this as I have a V12 with 4 carbs synchronization is key to performance from multiple carbs

probably just the idle set to low - raise it and see if she is OK

 

[flyingscott]

You do not need to balance carbs on a 2 strk outboard. The butterflies must all be closed tightly before you can do a link and sync.