1995 Suzuki 30hp high idle RPM

[Pappy58]

Just purchased a 1995 Suzuki 3 cyl. short shaft tiller with manual and electric start. After initial inspection the engine was started and run on a hose, shifted and so on for me. Initially the engine started with a high idle then idled down to a nice smooth idle. That was on Friday. Took the boat to the lake today (Sunday) for some fishing and the engine never idled down at all. Stayed up around 1200-1500RPM. The engine appears to be running cold and not warming up at idle. I did check the idle stop screw and it is backed off (plus the engine had already idled down at least once). Am thinking there must be a connection to the engine not warming, thinking that the engine should reach a certain temp then idle down? Thanks in advance for any help.

 

[99yam40]

Re: 1995 Suzuki 30hp high idle RPM

not sure on Suzuki but Yamaha motors have temp sensor tell CDI motor is warm so it will retard timing to slow idle RPM
Might check stat and temp sensor

 

[Pappy58]

Re: 1995 Suzuki 30hp high idle RPM

Have verified engine is running cooler than it probably should at idle. Probably less than 100F. Is the purple/white on the sender supposed to go to ground when the engine warms to a certain temp? What then controls overheat warning if any on this engine?
Also verified that the timing is around 22-25 degrees BTC at idle which is wayyyy too high.

 

[99yam40]

Re: 1995 Suzuki 30hp high idle RPM

All I can recommend if pick up a service manual for your motor and see what the specs are, along with how everything works.

If running that cold may need to pull and test stat to make sure it is functioning properly

 

[stylesabu]

Re: 1995 Suzuki 30hp high idle RPM

check t=stat it will probably be open when you remove it. if it is bad. there is also a fast idle choke soliniod but the fact that its running cold makes me think t-stat

 

[Pappy58]

Re: 1995 Suzuki 30hp high idle RPM

I don't see a fast idle choke solenoid on this engine. Strictly a manual choke. Specs on the timing at idle are in the range of 8 degrees ATC and mine is running at around 22 degrees BTC hence the fast idle. I can see minimal adjustment range of around 3-4 degrees from the TPS on a timing light. Started the engine yesterday and gradually reduced water flow to the engine until the pump was barely putting out. Not enough to completely fill the powerhead. By doing this I was able to warm the powerhead to around 130-140 degrees. Engine never reduced RPM and timing even though it was now warmed up.

 

[99yam40]

Re: 1995 Suzuki 30hp high idle RPM

Manual should help out testing all the inputs to CDI.
On my Yamaha CDI advances timing some but not that far for cold start and warm up, so maybe you have a CDI problem.
Will not know for sure until you test everything

 

[James R]

Re: 1995 Suzuki 30hp high idle RPM

You can disconnect the TPS and the electronics will default to a normal setting. This is a simple way to check if the TPS is causing the problem. I dont remember if there is an Idle potentiometer on your motor but if there is this can also cause your symptom if not working correctly. Going on from there it may be the Electronic module although usually very reliable.

 

[Pappy58]

Re: 1995 Suzuki 30hp high idle RPM

Thanks for the reply. I have the potentiometer on the TPS. Used an insulated driver to make the adjustments to it and no difference. Will disconnect and see what happens.

 

[larryhere]

Re: 1995 Suzuki 30hp high idle RPM

I have an older, 1986 suzuki 150 that uses a throttle position switch , which controls the timing for idle and advancement! mine ended up being a rusted pins in the plug going to cdi! easy to check with vom. at idle black and green/red short/ turn trottle up to 1/2 and up and black and brown/yellow are short all other position/connect is open! switch is on side of carb and linkage! something to check!