Jump to content

Mercury Optimax 90hp Oil Level Sensor


Recommended Posts

In the seemingly never ending saga of the engine on our boat, we took it out for the first launch on Saturday. Weather wasn't good but we just wanted to test the boat with the new engine so happy to just stick to sheltered waters around Calshot.

Didn't start well when the engine wouldn't start but that was quickly diagnosed to me forgetting to put the kill cord on. Engine started, we push off the trailer and it died. Restarted poodled around while I parked, and that was it. Wouldn't rev mush over idle and kept cutting out. My boat mate who was on the boat managed to coax it to the jetty by the slip where we fiddled with the vessel view app and checked wiring etc to no avail. I tied a long line to the front and pulled it back around to the slip and back on the trailer.

 

There are 2 faults in the app:

711-24 Oil level sensor - The input circuit for the sensor is above the valid limit. Oil level sensor in the tank is not working properly. Check oil level before continuing engine operation.

451-25 Pitot pressure -  The input circuit for the sensor is below the valid limit. Pitot sensor is not working properly 

 

From a bit of googling the second one is probably because there isn't a pitot sensor on the engine and its just the first one that we need to worry about. Seems the floats in the tanks have a magnet on them that falls off and a new tank is £500, a new sensor is £45.

 

Any one on here got experience of repairing the tank rather than replacing? Already spent far too much on this engine. Tempting to bypass the sensor but if we were to run out of oil and wreck the engine properly it would make the new tank seem cheap...

Link to comment
Share on other sites

2 hours ago, LostPiker said:

In the seemingly never ending saga of the engine on our boat, we took it out for the first launch on Saturday. Weather wasn't good but we just wanted to test the boat with the new engine so happy to just stick to sheltered waters around Calshot.

Didn't start well when the engine wouldn't start but that was quickly diagnosed to me forgetting to put the kill cord on. Engine started, we push off the trailer and it died. Restarted poodled around while I parked, and that was it. Wouldn't rev mush over idle and kept cutting out. My boat mate who was on the boat managed to coax it to the jetty by the slip where we fiddled with the vessel view app and checked wiring etc to no avail. I tied a long line to the front and pulled it back around to the slip and back on the trailer.

 

There are 2 faults in the app:

711-24 Oil level sensor - The input circuit for the sensor is above the valid limit. Oil level sensor in the tank is not working properly. Check oil level before continuing engine operation.

451-25 Pitot pressure -  The input circuit for the sensor is below the valid limit. Pitot sensor is not working properly 

 

From a bit of googling the second one is probably because there isn't a pitot sensor on the engine and its just the first one that we need to worry about. Seems the floats in the tanks have a magnet on them that falls off and a new tank is £500, a new sensor is £45.

 

Any one on here got experience of repairing the tank rather than replacing? Already spent far too much on this engine. Tempting to bypass the sensor but if we were to run out of oil and wreck the engine properly it would make the new tank seem cheap...

If the oil alarm is activated, the optimax goes into limp mode, which means it wont rev.

Do you have an engine tank as well as a main tank, if yes, the you have to prime and bleed the engine tank.  Just take the lid off and run the engine until the tank fills, then refit the cap.

Link to comment
Share on other sites

1 hour ago, GPSguru said:

You can ( and a lot of users do) epoxy the magnet back onto the float.

Not all the opti’s have the float switch, but a wiring fault gives the same alarm.

Is your tank like this ? 
 

63AE5413-347C-4DA8-8F6D-3DD06E2F3B66.thumb.gif.e847a90ec415eb8c4902761c49a5fb92.gif

Unless I'm missing something I'm pretty sure we just have the engine tank. I had a look but to be honest I was so pissed off that it still didn't work I didn't look properly but how do you get in to the float to glue the magnet back on? Looked a bit like a ship in a bottle to me and would need an gynecologist to get to?

Link to comment
Share on other sites

1 hour ago, GPSguru said:

You can ( and a lot of users do) epoxy the magnet back onto the float.

Not all the opti’s have the float switch, but a wiring fault gives the same alarm.

Is your tank like this ? 
 

63AE5413-347C-4DA8-8F6D-3DD06E2F3B66.thumb.gif.e847a90ec415eb8c4902761c49a5fb92.gif

can you link to where you got that image from?

Link to comment
Share on other sites

When I had a piece of crap 90 merc two smoke, the oil chamber needed to full and the engine trimmed down fully. I had much the same issue where it cut out, so went through checking isolation switches etc etc but when I turned off the battery and back on with the engine key still in the on position, it burnt out the electrical rectifier (costing $500). With mine the oil reservoir needed to always be a minimum of 3/4 full . Soon replaced it with a Yam 4 stroke 70 which surprisingly gave much the same performance but without the high fuel use (once propped right).

Edited by JDP
Link to comment
Share on other sites

5 minutes ago, JDP said:

When I had a piece of crap 90 merc two smoke, the oil chamber needed to full and the engine trimmed down fully. I had much the same issue where it cut out, so went through checking isolation switches etc etc but when I turned off the battery and back on with the engine key still in the on position, it burnt out the electrical rectifier (costing $500). With mine the oil reservoir needed to always be a minimum of 3/4 full . Soon replaced it with a Yam 4 stroke 70 which surprisingly gave much the same performance but without the high fuel use (once propped right).

That’s gonna cheer him up no end 🤣

Link to comment
Share on other sites

9 minutes ago, JonC said:

That’s gonna cheer him up no end 🤣

It should do if its simply a case of keeping the oil topped up ahead of every trip instead of every three trips like I was trying. Once I found out, I could simply keep it filled and not have issues. The rectifier was a known issue is you did what I did and turn on the battery isolator while the engine was in the start position, if I had known before hand I possibly wouldn't of made the mistake.

Also, it was simply a bit of a piss take on the merc, they are very good motors these days, I would happily buy another (already have a 75 merc 4 stroke which has been faultless).

Edited by JDP
Link to comment
Share on other sites

4 minutes ago, JDP said:

It should do if its simply a case of keeping the oil topped up ahead of every trip instead of every three trips like I was trying. Once I found out, I could simply keep it filled and not have issues. The rectifier was a known issue is you did what I did and turn on the battery isolator while the engine was in the start position, if I had known before hand I possibly wouldn't of made the mistake.

Are these units too clever to be run pre mixed? I’ve had two strokes that had been hard wired so to speak, but they were a lot older. 

Link to comment
Share on other sites

2 minutes ago, JonC said:

Are these units too clever to be run pre mixed? I’ve had two strokes that had been hard wired so to speak, but they were a lot older. 

Ive done the same with older ones but was advised not to on the newer ones. I stay way from doing much to my outboards and leave it to the mechanic, who comes to my house to work on any engines I need looking at. The mechanic has a commercial boat that I often skipper, so looks after me well in terms of priority and price.

Edited by JDP
Link to comment
Share on other sites

1 minute ago, JDP said:

Ive done the same with older ones but was advised not to on the newer ones.

It would be easy to leave the tank full and bypass it but I don’t understand the elastictrickery on these things. 

Link to comment
Share on other sites

8 hours ago, LostPiker said:

can you link to where you got that image from?

Yes, it came from boats.net, and Suzook12 has kindly placed the link.

The opti is actually a very good engine, and when running properly is also very reliable. The oil injection system is somewhat complex, put generally apart from the 'oil level' issue, give very little problems. The opti always had a reputation regarding the oil injection, as some used to just sip oil and others used to drink oil, but there seemed to be no reason for the difference and the usage and performance was similar.

If you get the opportunity, it maybe wise, to have a marine grease monkey who is very familiar with the opti to take a look at it, as some of the fault symptoms and codes are not what they seem (a bit like cars).

There are several thread on the USA site 'Hull Truth' that relate to your issues, but be warned, Hull Truth can be quite toxic at times, but equally a good source of info from a good number of folk that know what they are talking about.

Link to comment
Share on other sites

On 3/21/2023 at 10:52 PM, GPSguru said:

Yes, it came from boats.net, and Suzook12 has kindly placed the link.

The opti is actually a very good engine, and when running properly is also very reliable. The oil injection system is somewhat complex, put generally apart from the 'oil level' issue, give very little problems. The opti always had a reputation regarding the oil injection, as some used to just sip oil and others used to drink oil, but there seemed to be no reason for the difference and the usage and performance was similar.

If you get the opportunity, it maybe wise, to have a marine grease monkey who is very familiar with the opti to take a look at it, as some of the fault symptoms and codes are not what they seem (a bit like cars).

There are several thread on the USA site 'Hull Truth' that relate to your issues, but be warned, Hull Truth can be quite toxic at times, but equally a good source of info from a good number of folk that know what they are talking about.

Thanks. I had Barry at Winsor Marine service it, and have the shift rod straightened already. As I'm already £2k into a supposedly good engine I think I'll bypass the sensor and take it for a trial before I spend any more on it

Link to comment
Share on other sites

  • 4 months later...

Little update, it gets worse. I think I managed to buy the worst outboard available in the UK.

Tried to bypass the sensor and it still didn't work, bought a new sensor and tried to trick it with a magnet. No change so I gave in and took it to a Mercury dealer.

Some good news is the tank is fine, the float was held down by sludge which when cleaned works perfectly and no oil errors and the compression is fine. Almost nothing else is though.

All 3 fuel pumps either need rebuilding or replacing

Alternator mounts perished

Throttle not opening fully

throttle body linkage seized

Battery undersized

Engine harness cut into and damaged

Air filter very old and damaged

fuel filter damaged

Another £2k bill to put it right🥺

 

by the time its back in the water will have spent what I could have got a brand new engine for. Painful and expensive lesson learn 

 

Link to comment
Share on other sites

1 hour ago, LostPiker said:

Little update, it gets worse. I think I managed to buy the worst outboard available in the UK.

Tried to bypass the sensor and it still didn't work, bought a new sensor and tried to trick it with a magnet. No change so I gave in and took it to a Mercury dealer.

Some good news is the tank is fine, the float was held down by sludge which when cleaned works perfectly and no oil errors and the compression is fine. Almost nothing else is though.

All 3 fuel pumps either need rebuilding or replacing

Alternator mounts perished

Throttle not opening fully

throttle body linkage seized

Battery undersized

Engine harness cut into and damaged

Air filter very old and damaged

fuel filter damaged

Another £2k bill to put it right🥺

 

by the time its back in the water will have spent what I could have got a brand new engine for. Painful and expensive lesson learn 

 

Then I hope you are going to put the money toward a new one and not waste any more time on this one!!

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...