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Author Topic:   2004 170 90 OptiMax alarm
dcritch posted 07-11-2006 12:07 PM ET (US)   Profile for dcritch   Send Email to dcritch  
My 90 Optimax recentely had its annual service at the local Mercury Service shop. Now I get random occational beeps from the warning buzzer when sitting at the dock in neutral or trolling at lowest throttle (700 rpm). Engine runs great and does'nt appear to have any problems. Only other change this season has been the addition of two new batteries. Has anyone else had this problem?
bsmotril posted 07-11-2006 01:32 PM ET (US)     Profile for bsmotril  Send Email to bsmotril     
Look for a loose or corroded battery cable terminal on one of the batteries. Those intermittent alarms are often low battery voltage. BillS
sosmerc posted 07-11-2006 03:09 PM ET (US)     Profile for sosmerc  Send Email to sosmerc     
Do you have a system monitor installed? If so, do you get a "check engine" symbol when the alarm sounds?
If the alarm sounds, there should be a code stored in the engine computer...your mechanic can access that with his DDT diagnostic tool. He can clear the codes, test run and then see if any further codes appear.
If no codes appear, yet you still get an intermittant horn...I'd be looking at a momentary loss of battery power due to a poor connection somewhere...or a bad keyswitch.
What is the engine temp at the time of the alarm?
dcritch posted 07-12-2006 01:36 PM ET (US)     Profile for dcritch  Send Email to dcritch     

I tightened my battery connections(all new cables in last 12 mos)and still get warning buzzer operating on either battery.


I don't have smart gauges so I can't monitor temp. I do plan on adding the gauges because my 170 is wired for them. I'll have the shop check the ignition switch.

The one senario in my engine manual which comes close to what I'm experiencing is;
Function: Engine Running Cold at Slow Speed
Sound: On Beep
Description: Engine is not reaching correct temperature while operating below 1000 RPM. Have your dealer check the engine.

Would this suggest a thermostat or impeller issue?

Any thoughts are much appreciated.

ivansfo posted 07-12-2006 08:17 PM ET (US)     Profile for ivansfo  Send Email to ivansfo     
Sounds similar to an issue I had with my 2001 Optimax. After about 1.5 years, the alarm kept going off when idling for more than 10 minutes or trolling at slow speeds near idle. The motor ran and was peeing just fine. I have Smartcraft gauges and the I recall it said something about water pressue.

Took the boat to the dealer and they diagnosed the problem to be impeller and popit valve? Popit was replaced under warranty but I had to pay for the impeller job. After this, the motor has been running alarm free.

bsmotril posted 07-14-2006 09:15 AM ET (US)     Profile for bsmotril  Send Email to bsmotril     
It could be either impellor, or T stat. The T stat is a lot easier to get to for a visual inspection than is the impellor. Easy to test also; put it in a pan of water on the stove over medium heat. Put a meat thermomoeter in the water, and monitor the temperature at which the thermostat opens. But if the problem is the motor running cold, it would be because the thermostat is not closing all the way, and you should be able to see that by pulling the housing where it sits and just looking at it. If the impellor is more than two years old, change it regardless, it is due for replacement. BillS
dcritch posted 07-17-2006 12:28 PM ET (US)     Profile for dcritch  Send Email to dcritch     

I appreciate your comments. I need to install the smartcraft gauge. I googled "optimax popit valve" and it took me to a Whaler forum discussion of a similar issue by bkloss 7-11-05. Sounds like low rpm temperature fluctuations happen from time to time with with OptiMax.


Thanks again. Seems like every shop I talk to has a different idea about cost to replace impeller ranging from $200 to $350. I've always replaced my own on inboard ski boats but am reluctant to operate on the OptiMax while still under warrenty.
A friend of mine who is in the industrial bearings and belt business took a look at the alternator belt (Which the service shop said needed to be replaced but had to order the belt) and was suprised by the amount of ware after 100 hours. The belt was very cracked and missing chunks in places. In the future I will carry extras.

dcritch posted 08-06-2006 10:55 PM ET (US)     Profile for dcritch  Send Email to dcritch     
I replaced the impeller myself (very easy on the 90 Optimax) but problem remained. I took the boat back to Lake Union Searay (My dealer) and it turned out to be a bad coil. At slow speed the engine was not getting up to temperature. The dealer had to call in the area rep for mercury before they could figure it out. Thankfully my warrenty covered it.

The impeller I replaced looked like new but because it is so easy to replace I'll probably do so every couple seasons.

ivansfo posted 08-07-2006 05:47 PM ET (US)     Profile for ivansfo  Send Email to ivansfo     

Glad you got it fixed. I would have never thought it could be a bad coil. I too learned how to change out the impeller on the Optimax this year. Now that I know how to do it myself, I won't hesitate to change it out every 2-3 years.


dcritch posted 08-07-2006 09:00 PM ET (US)     Profile for dcritch  Send Email to dcritch     

It took them several hours to figure it out. The 90 Optimax is an inline 3 cylinder engine and the bad coil was on the center cylinder. The engine did'nt appear to have any problems at speed because the computer was compensating for the one weak cylinder. At slow speed the engine was not reaching temperature and the computer was trying to compensate by demanding more fuel. This resulted in some noticeable exhaust fumes at slow speeds below 1000 rpm.

The impeller went smoothly even though I did'nt have the motor shifted into forward gear to facilitate easy realignment of the shift rod. I assumed positioning the shift handle to forward with the engine off would do the trick however I did'nt check the prop before dropping the lower unit. As it turned out the coupling on the exhaust housing and the shift rod on the lower unit both "clicked" into forward gear when each was manually turned slightly. The lower unit slid up snug on the first try.

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