View Full Version : Optimax 150 still in limp mode?

01-08-2019, 06:03 PM
I ran my boat low on oil in the summer of 2017. The boat gave me the beeping warning and I filled the main oil reservoir up with oil and the reserve reservoir with oil. I took my boat back out on the water a little later and the same thing happened, the boat's warning beeps went off and the boat went into limp mode and would not rev-up. I got home and called a boat tech and he told me about the low oil sensor needing to be reset. He had me unplug the sensor and plug it back in. I fired the boat up in my drive way with muffs and sure enough, the warning beeps went away. I then put the boat away for the winter.

So this past summer I fired up the boat on the lake and it kind idled like crap to where it didn't really want to run at all. I just figured it was normal coming out of winter and I tried to get the boat up on plane. It took for ever to get going and would not go above 3000 rpm. In hindsight, it was almost like it was in limp mode again without the warning beeps. I ran it all day thinking it was bad gas because it didn't want to idle real good. As I was ripping around the lake that day, occasionally it would kick up to 4000 rpm and then drop right back to 3000 rpm. At the end of the day while coasting into the dock, the rpm kicked up a notch so I took it back out for one more trip around the lake and it jumped up to 5000 rpm, so I thought that I had blown the bad gas out.

The next time on the lake, the same thing happened. I was back at 3000 rpm for a while. Then it would jump to 4000 rpm for a while, then back to 3000, then up to 4000. Than all of a sudden it went to 6000 rpm, so I thought I had my old boat back.

The next time on the lake, it started all over again...3000 rpm for a while, then 4000, then back to 3000. This time I couldn't get it back to 6000 rpm.

I was thinking it was the gas, but now I am thinking it is in-and-out of limp mode. Does anyone have any suggestions? It is a 2008 fuel injected Mercury Optimax 150. I have it back in winter storage right now and I have a guy who wants to buy the boat, but I don't want to sell him a boat with problems. The boat tech that helped me before is no longer in business and I am 100 miles from the nearest technician. My latest hunch is that it might have a bad battery. The battery is 10 years old, but I have never had a problem with it starting and no warning signs coming from the dashboard.


01-21-2019, 04:27 PM
I had my motor into the shop to see what they could figure out with my boat. The technician said that the problem is how the kicker motor is plumbed into the main fuel line. It is plumbed in by using a simple tee-connection into the main fuel line, right in front of the big motor. The technician said that the big motor could be sucking air from the fuel line to the kicker motor if that line isn't full of fuel. He said that I need to either put a ball-valve in where the tee is so that I can turn the kicker fuel line on and off. Or, I can simply disconnect the fuel line to the kicker motor because there is a quick connect. This diagnosis makes sense to me because I noticed that the big motor ran better after I ran the kicker motor, but I won't know this for sure until I can get the boat back on the water. Does this make sense to you guys?

01-21-2019, 08:36 PM
Sure does.

01-22-2019, 10:46 AM
It makes sense to me, but my dad asked me a question that I really needed to think about and do some more research on. He asked, why did this problem begin all of a sudden. The motor is a 2008 and I have not had any problems with it until last summer. The research tells me that the gas bulb that you pump up, in the kicker motor gas line must be going bad.

There is a water/gas separator in the main gas line before the tee. After the tee, there is a gas bulb in each fuel line going to each motor. I guess that the valve in the bulb going to the kicker motor is going bad. If I don't run the kicker motor before I run the big motor (which is usually what happens when you hit the lake), then the kicker motor is pulling air from the gas line going to the kicker motor. When I run the kicker motor, that gas line is completely full of fuel and the big motor can no longer pull air from that gas line.

Now I gotta figure out the best fix. Do I replace the tee with a ball valve so that I can shut off one of the fuel lines when that motor is not in use? Or, do I just disconnect the fuel line to the kicker motor when not in use? If I just disconnect the fuel line to the kicker motor, am I going to be dealing with a little bit of fuel spraying/dripping from the connection when I disconnect? Is there anyway there can be a little bit of air being sucked through that fuel connection when disconnected.

Let me know your thoughts.


01-22-2019, 10:53 AM
A 10 year old battery on a computer controlled motor , why ??--------Yes I believe the big motor can suck air into the fuel supply side via the kicker fuel line.----You need the right components to correct that possibility.

01-22-2019, 11:08 AM
What are the right components? Replace the tee with a ball valve or simply disconnect the fuel line from the kicker motor?

Should I replace the gas bulbs?

Should I replace the 10 year old battery? The technician said the battery held a good charge after running the big motor for 1.5 hours.

Here is the bigger issue...I just sold the boat to a family friend. I am storing it until late Spring until he can come and get it. I want to make sure it is in perfectly running condition before he takes it.