Trolling at idle/slow speed on 2 stroke 1989 70hp engine help

[flyhigh123]

I recently purchased a boat and it has a 1989 2stroke 70hp Johnson VBO engine.

I do some trolling around 2-3mph. When I do troll, I run into some issues as the engine seems to have a hard time keeping at a slow troll and will die after 10-20 minutes at troll speed. I just dropped of the boat to mechanic to get the engine inspected and basic maintenance.

Does anyone have experience with a similar type of engine? What are some tips and tricks for these older engines to troll?

If I get a troll plate and give it a little more gas, does that work and help avoid the oil build up etc?

Any help and thanks!

 

[boobie]

Re: Trolling at idle/slow speed on 2 stroke 1989 70hp engine help

There's a lot of things involved but you should wait for your mechanics verdict and then get back to us.

 

[Rollinunknown]

Re: Trolling at idle/slow speed on 2 stroke 1989 70hp engine help

Ive had 3 Evinrude's 78/94/96 Zero problems trolling . But i do change my plugs yearly (only 2 of them) and i run 10oz of seafoam every 3-4 tanks (6gal's) fuel.I can not say seafoam works but i never had problems and my plugs always looked good.

I mixed my fuel at 50:1 sometimes i ran walmart oil other times i ran QuickSilver never a difference that i could pick up.

I could throw my motor in gear and troll around all day just like my buddy's 4-stokes do.

The current 115hp dose the same also.

 

[Kalidor]

Re: Trolling at idle/slow speed on 2 stroke 1989 70hp engine help

Had the same problem with my 1984 60 HP and I rebuilt the fuel pump with new diaphragm and gaskets problem gone. Got the idea from my manual in the trouble shooting tips.

 

[flyhigh123]

Re: Trolling at idle/slow speed on 2 stroke 1989 70hp engine help

Here is a list that i've compiled that could be wrong, if anyone can suggest other issues, please let me know:

Carb needs rebuild
Float valve is not level?
Adjust idle valve ( 2-4 turns)
Spark Plugs old ( someone suggested moving a step up "hotter" to better burn the oil/fuel)
fuel pump
Suggestion of using premium gas


Anything else for me to check on?

If I am able to troll at Idle speed, that is ideal.

Any thoughts on adding a trolling plate and raising the RPM?

 

[steelespike]

Re: Trolling at idle/slow speed on 2 stroke 1989 70hp engine help

Idle speed should be about 700.
Speaking very generally 2 strokes usually have A" bleeder valve",my term, that drains excess fuel out of the crankcase.
Older motors dump into the water yours probably recirculates it into the intake.
This can produce idle problems.As suggested a leaky fuel pump diaphram could cause it to load up and dump more fuel into the intake.

 

[flyhigh123]

Re: Trolling at idle/slow speed on 2 stroke 1989 70hp engine help

What do you guys think about adding a 5-10hp kicker for trolling? How do I know what kind of a motor I need so I can attach it to my transom?

 

[Kalidor]

Re: Trolling at idle/slow speed on 2 stroke 1989 70hp engine help

Well A kicker works. That's what I run, but there are a lot of factors to look at. Do you have room on your transom to put the kicker. You may need to get a kicker bracket or jack plate. Then you need to look at how your going to steer it. Also need to think about how you will control it. Remote controls or just reach out the back to adjust throttle. you will want to size the motor as small as you can so your not adding too much weight to the stern. It all depends on what you want and how much money you want to spend. Most people run kickers for two reasons.
1) Can't get there main motor to run slow enough.
2) Save on fuel

It's all up to you and what you want from the boat.

 

[dodgeboy1979]

Re: Trolling at idle/slow speed on 2 stroke 1989 70hp engine help

i run a 4.5hp evinrude as a kicker, and it workd great. i have a 1976 70hp and i just hate trolling with it as it burns more fuel. I put a little jack plate on my boat and use the 70hp as a rudder when trolling and it seem to work great.

 

[flyhigh123]

Re: Trolling at idle/slow speed on 2 stroke 1989 70hp engine help

Well A kicker works. That's what I run, but there are a lot of factors to look at. Do you have room on your transom to put the kicker. You may need to get a kicker bracket or jack plate. Then you need to look at how your going to steer it. Also need to think about how you will control it. Remote controls or just reach out the back to adjust throttle. you will want to size the motor as small as you can so your not adding too much weight to the stern. It all depends on what you want and how much money you want to spend. Most people run kickers for two reasons.
1) Can't get there main motor to run slow enough.
2) Save on fuel

It's all up to you and what you want from the boat.

kicker will be the next option should i not be able to get the idle to idle well. The stalling will end up getting me stranded, so looking at all options.

 

[flyhigh123]

Re: Trolling at idle/slow speed on 2 stroke 1989 70hp engine help

Another issue i ran into was when i was in idle, the engine stalled on me twice when i was going to throttle up to speed. However, this was after it had already stalled a few times at Idle.

(was hoping that throttling up to speed would burn out any oil/fuel at WOT)

 

[Tim Frank]

Re: Trolling at idle/slow speed on 2 stroke 1989 70hp engine help

Here is a list that i've compiled that could be wrong, if anyone can suggest other issues, please let me know:

Carb needs rebuild
Float valve is not level?
Adjust idle valve ( 2-4 turns)
Spark Plugs old ( someone suggested moving a step up "hotter" to better burn the oil/fuel)
fuel pump
Suggestion of using premium gas


Anything else for me to check on?

If I am able to troll at Idle speed, that is ideal.

Any thoughts on adding a trolling plate and raising the RPM?

What plug are you running? Spec'd plug is champion QL77JC4 gapped at 0.030". You could open that up to 0.035" if they are fouling.
And are they old? If they are, you should certainly change them to rule out that as a cause.

 

[flyhigh123]

Re: Trolling at idle/slow speed on 2 stroke 1989 70hp engine help

What plug are you running? Spec'd plug is champion QL77JC4 gapped at 0.030". You could open that up to 0.035" if they are fouling.
And are they old? If they are, you should certainly change them to rule out that as a cause.

Hi tim! very good info! Someone said that running "hotter" plugs may help. Do you know what that means? Is that a different gap or a different plug and if plug, can you recommend one that runs hotter?

 

[rolmops]

Re: Trolling at idle/slow speed on 2 stroke 1989 70hp engine help

Go for the kicker. I use a 9.5 or 9.9 pushing a 19 foot Islander on Lake Ontario while salmon fishing and I love it. Just think of the extra safety in having 2 engines on your boat. If one poops out,you can always get back in on the other.

 

[Tim Frank]

Re: Trolling at idle/slow speed on 2 stroke 1989 70hp engine help

Hi tim! very good info! Someone said that running "hotter" plugs may help. Do you know what that means? Is that a different gap or a different plug and if plug, can you recommend one that runs hotter?

A hotter plug does not dispel heat away from the electrodes as quickly as a cooler one.
I'd check your owner's manual and see if they spec a hotter one....otherwise I'd stay with the OEM one.

You have not indicated whether plug fouling is the cause of the engine stalling. Have you pulled a plug or 2 immediately that it has quit?

Wait to see what your mechanic says for now.

How long have you had the motor? Have you ever replaced the plugs?

 

[flyhigh123]

Re: Trolling at idle/slow speed on 2 stroke 1989 70hp engine help

A hotter plug does not dispel heat away from the electrodes as quickly as a cooler one.
I'd check your owner's manual and see if they spec a hotter one....otherwise I'd stay with the OEM one.

You have not indicated whether plug fouling is the cause of the engine stalling. Have you pulled a plug or 2 immediately that it has quit?

Wait to see what your mechanic says for now.

How long have you had the motor? Have you ever replaced the plugs?

I'm waiting on the mechanic to come back with his findings. I didn't pull any plugs, so we'll see. I just purchased the boat, so it was actually my first time on the water. WOT was running great and even slower speeds. It was idling that caused issues.

 

[flyhigh123]

Re: Trolling at idle/slow speed on 2 stroke 1989 70hp engine help

here is an update:
Compression is good. Installed new plugs, cleaned out carb.

Got the boat back and it runs better, however not perfect.

The neutral idle has been raised to a litttle under 1,000 rpm and stays running.

However, when I put the boat into drive, if the RPM is under 1,000, it still stalls on me. If i bring the RPM above 1,000 then the boat runs fine.

Any ideas what is causing the boat to still when the RPM is under 1,000?

I also got a trolling plate. When the trolling plate is down, the engine will stall when the rpm is less than 1,300. I think the back pressure is doing something to the engine.

Thanks for all the help!

 

[steelespike]

Re: Trolling at idle/slow speed on 2 stroke 1989 70hp engine help

Here is a list that i've compiled that could be wrong, if anyone can suggest other issues, please let me know:

Carb needs rebuild
Float valve is not level?
Adjust idle valve ( 2-4 turns)
Spark Plugs old ( someone suggested moving a step up "hotter" to better burn the oil/fuel)
fuel pump
Suggestion of using premium gas


Anything else for me to check on?

If I am able to troll at Idle speed, that is ideal.

Any thoughts on adding a trolling plate and raising the RPM?

No, don't use premium gas.
Does the motor idle for docking and no wake zones?

 

[flyhigh123]

Re: Trolling at idle/slow speed on 2 stroke 1989 70hp engine help

No, don't use premium gas.
Does the motor idle for docking and no wake zones?

if the motor is in drive ( forward) idle, it will stall. I need to get the RPM above 1,000 in order for it to run without stalling

 

[flyhigh123]

Re: Trolling at idle/slow speed on 2 stroke 1989 70hp engine help

bump for more ideas?