thermostat question

[redman09]

My 90 hp johnson ocean runner started having idle problems a little while ago and started this chain of events, anyways during this I found that I had been running my boat without thermostats for quite some time, so I wanted it to be right so I ordered some along with some springs and put them in, now since Ive done that along with go through the carbs and throttle body plates and replaced the power pack now it idles at 1600 rpms, I did not adjust anything I just cleaned them and put them back on, will thermostats make the motor idle different as I have been told that it will? Is this normal? The guy who told me that the power pack wouldnt fix my original issue, I hate saying this but you were correct sir!

 

[rscotth]

Re: thermostat question

From my experiences over the years your thermostat issue would not effect the idle as significantly as yours (600 rpm). It's pretty safe to say it's in the carb adjustment or possibly a bad gasket sucking air since you had them apart. I have replaced failing power packs and coils that changed the idle a couple hundred rpm's.

Here in north east florida it is a quite common practice to remove the thermostats with no ill effects to idle or carbon buildup even with hours of trolling. This is only done on non computer controlled engines like the older crossflows. To me it seems like just pulling out the thermostats creates a huge increase of flow that even a fully open T stat could never replicate. I epoxied in some 1/4" washers into the original t stat plate for a restriction trying to duplicate the flow of the t stats. Once I did that I was concerned that the washers would eventually liberate and so onto version 2.0.
The second version I made my own t stat plate and replaced the t stat holes with calculated orifice sizes based upon full open of the t stats I took out. So far this has worked great............

 

[schematic]

Re: thermostat question

Check your ignition timing at idle. Maybe its staying in "Quick Start" if so equipped. This will give you 10+ deg at idle causing fast idle. Also be sure you synchronized carb to carb properly.

 

[redman09]

Re: thermostat question

now my idle on a cold start is at 1000 rpms then after a few secs it revs up to 2000 rpms? would quick start cause this to happen? the power pack is brand new, temp sensor maybe? im lost at what is causing this please help!

 

[schematic]

Re: thermostat question

I would start with a proper "Link n Sink" then move on to checking timing at idle to see if quick start is functioning properly. Quick start advances timing until "temp sensor" signals "warm engine". The result of quick start should not give 2000 rpm if link n sink is correct.

 

[redman09]

Re: thermostat question

what controls the timing on this engine? The optic sensor?

 

[schematic]

Re: thermostat question

the optic sensor on OIS2000 ignitions supplies the pack with idle timing and max timing and everthing in between according to throttle position. The pack decides (by using temp signal) whether to add an extra 10 deg for a "poor mans fast idle"


I haven't checked to see if you have OIS2000....

 

[redman09]

Re: thermostat question

it has OIS2000, thats why I was unsure what controlls the timing, its different from any other outboard Ive worked on, would that sensor cause this if it was going bad or do these sensor just quit when they go bad?

 

[schematic]

Re: thermostat question

The sensor can cause nasty intermittent problems. Don't take stabs in the dark. Get the "Link n Sink" done first. Get a manual for this. The idle speed on that system is set by a plastic domajiggy. I'll bet your "LINK n SINK" is a mile out.....You must familiarize yourself with the system as its not conventional.

 

[redman09]

Re: thermostat question

ok thank you so much you have cleared things up for me on the OIS2000 system Im gonna do a link and sync and will post my results once its done thanks again!

 

[schematic]

Re: thermostat question

I forgot to mention.....be sure you have the correct plugs and wires on the unit. either one can cause problems from RFI.
Probably need QL78YC