1997 150 HP Mariner Sudden high idle and shifting problems

[rwjhenry]

Hello. I have a 1997 Mariner 150 HP Outboard on my 1997 Maxum 1900 XR boat. The motor serial number is OG549337.

Last week, while on the water, the idle speed suddenly became very high. In addition, once in fwd (which clunked a lot due to the rpms), I could not get it back into neutral. If i shut off the engine, I could move to neutral fine. I suspect the shifting problem is due to the high idle speed? It idles at roughly 1500+ RPM in the water. When I came home to flush it, it idled as high as 3000 RPM! The shifting problem was similar from reverse to neutral although I could do it, it was quite stiff and clunky though.

I looked under the engine cover and saw the sliding link for the shifter. There is a "N" mark on it and when I put it in neutral, it is not centered on the mark.

This is my first boat and i don't really know what to expect.

Thank you for the help.

 

[Chris1956]

Re: 1997 150 HP Mariner Sudden high idle and shifting problems

Well, it could be alot of things, easy to complex. Lets start with easy stuff. Make sure the throttle cable pushes the throttle closed when in neutral. If not, maybe the control is bad, or the cable slipped.

If that is OK, look to see if the carbs have a thermal control on them. This allows the motor a little extra air when she is cold. When she warms up the extra air is closed off. Make sure the fitting wasn't broken or the hose wasn't pulled off.

Make sure the trigger linkage is still attached. After that, we are looking at a faulty idle stabilizer, or something I have not thought of.

Post back with results.

 

[carholme]

Re: 1997 150 HP Mariner Sudden high idle and shifting problems

Your s/n comes up as:

MARINER - (150 H.P. (1997 ))
Serial No: 0G549337 Model No: 7150412FD

Parts List for model 7150412FD:

135/150/175/200 XR6 MAGNUM III 105-140 JET - Mercury, Mercruiser, Force, etc. Parts Lookup

The service manual you require is P/N: 90-824052 and I can send you a copy if you PM me with an email address.

Gerry

 

[rwjhenry]

Re: 1997 150 HP Mariner Sudden high idle and shifting problems

Chris1956, I pulled off the airbox and it looks like the butterflies close completely. I am outside looking it over right now. There is a device connected to the carburetor that appears to be an electrical solenoid of some sort. It has a hose that connects to cylinder #3 and goes to the top carb. From there it jumps through all 3 carbs coming out the back (exit - engine side). The "solenoid" has two wires coming off and are connected to terminals on the side of the engine (starboard). I really don't know if I am looking at the right thing though. I am getting the manual from Gerry and will confirm. It looks like there is a mechanical button on top of it. It presses in a bit - maybe a reset?

One thing i noticed with the throttle handle - it doesn't feel like it has any free play in the neutral position. However, the linkage does have free play at neutral position of the throttle. I believe the throttle handle used to have some free play.

I have the battery disconnected right now as I read on another post saying that it could reset the auto choke.

My question is: a choke should restrict the gas and lean out the mixture right? This would make the engine rev up. Too much gas should bog it and make it stall. Again, I know 2 stroke bike and ATV engines but not boats.

I don't know what you mean by "trigger linkage". I don't know where to look.

Thanks,

Richard

 

[Faztbullet]

Re: 1997 150 HP Mariner Sudden high idle and shifting problems

look to see if the carbs have a thermal control on them. This allows the motor a little extra air when she is cold. When she warms up the extra air is closed off.

Close but backwards, its closed when cold making idle mixture richer and opens up to lean mixture. Will not cause a high idle as if stuck closed or blocked it would idle lower as it rich.

here is a device connected to the carburetor that appears to be an electrical solenoid of some sort. It has a hose that connects to cylinder #3 and goes to the top carb.

That is the enrichener.....(choke)

It looks like there is a mechanical button on top of it. It presses in a bit - maybe a reset?

Sorry but no as that how you manually choke engine to start it....

I have the battery disconnected right now as I read on another post saying that it could reset the auto choke

Sorry again but nope as no electrical auto choke feature.....

a choke should restrict the gas and lean out the mixture right?

Nope..closing a choke causes more vacuum to pull thru primary's increasing the air/fuel mixture (rich)
Check the primary pickup timing screw on throttle/spark arm to see if it has backed out as this will cause this along with a stuck shift switch as this advances timing about 3-4? when you shift to keep engine from stalling....

 

[rwjhenry]

Re: 1997 150 HP Mariner Sudden high idle and shifting problems

You were right. I started the engine and the idle is still about 2000 rpm and climbing. I confirmed the enrichener is working by pressing in the key. The solenoid clicked. This also helped start the engine right away! Good thing to know.

Sorry but i don't know what "primary pickup timing screw on throttle/spark arm" is. Can you please explain? I have attached an image of the linkage. It doesn't appear that any screws are backed out but maybe one is... I assume i should check when running I just don't know which to mess with.

Is there a way to check that the thermal control functions correctly?

Thanks for the help!

 

[rwjhenry]

Re: 1997 150 HP Mariner Sudden high idle and shifting problems

OK, so I just started the engine and got 2000+ rpm. I then adjusted what I think is the idle speed screw. Please see the attached picture with the red circled screw. I backed it out with the engine running and was able to drop the idle to about 1000-1100 rpm. This was with the screw backed out to the point of no contact to the stopper. This is almost there but not quite 650-700 as required. I tried shifting into fwd and rev and back to neutral with success. However, shifting to forward increases the idle to about 1500 rpm. Shifting to reverse worked and made no change to rpm (1000-1100 rpm). In both, i was able to go back to neutral OK but harder from, fwd since the rpm was high. Is it normal to have the idle increase in fwd but not reverse? It might be different on the lake.



To test the idle in gear, I tried manually pulling the linkage in pink to the right. This seemed to do the trick. Should I be adjusting the screw circled in green to fix this?

Is my "idle" screw too far back now since it does not contact the stopper plate anymore?

Thank you guys. This is a real help to me and I appreciate the immediate responses!

Best regards,

Richard

 

[Chris1956]

Re: 1997 150 HP Mariner Sudden high idle and shifting problems

Cable should push throttle closed, when throttle handle is in neutral. Lowest adjustment looks to be idle stop. It is partially unscrewed, but you need to adjust the throttle cable barrell nut to make it push the throttle closed.

 

[rwjhenry]

Re: 1997 150 HP Mariner Sudden high idle and shifting problems

So I didnt hear back from anyone and I decided to look through the service manual and try things. With the engine running, I manually forced the carb linkage to the closed position. This did help meaning the butterflies werebt closing all the way. I also noticed the oil linkage wasnt properly aligned with the factory mark. It was getting too much oil. I adjusted this to stock. I replaced the fuel filter and cracked open the old one. It was full of sand! Not sure how that can even gappen! I removed the intake cover and started the engine. Now my idle was close to 800. A small adjustent to the timing screw and the idle it at or below 750! Everything runs right nomw. Im going out this weekend I think so hopefully it works. I will report back.

 

[Faztbullet]

Re: 1997 150 HP Mariner Sudden high idle and shifting problems

A small adjustent to the timing screw and the idle it at or below 750!

That 750rpm is for engine in water with backpressure and in gear, on a hose it needs to idle at about 1100rpm .

 

[rwjhenry]

Re: 1997 150 HP Mariner Sudden high idle and shifting problems

Thanks. That is good news. I started it again last night and the neutral idle was about 700 and when I put it in gear it was about 1100. This makes me a bit more confident today. The lake is almost 60 miles away so quite a drive if it didnt run right. I am definitely bringing tools with me today. I need to get a bucket at home for testing I think. Thanks.