Honda 90hp carb engine kicking into safe mode

[jackd1023]

This is a friends boat and am lost. Ser# BF90A4LRTA 2004 honda 90hp 4 stroke carb. It is getting an intermittent alarm while at WOT. Changed plugs, filters, drive oil, engine oil, Impeller, as part of maintenance. They were still getting an alarm and kicking into "safe mode" I advised them to bring it into the Honda dealer to scan for codes. They were told "no codes" the marina water tested and could not duplicate the issue. But they were able to charge them 375.00 for their "diagnosis". I now feel some responsibility for this as I advised them and they still have the problem, Only under load and still Intermittent. I checked and cleaned all terminals. Please I dont know if this is common or someone can possibly give me some advice here, Thanks a lot.

 

[jackd1023]

Re: Honda 90hp carb engine kicking into safe mode

Anyone have a manual for this possibly?

 

[MattFL]

Re: Honda 90hp carb engine kicking into safe mode

Was the thermostat replaced?

 

[jackd1023]

Re: Honda 90hp carb engine kicking into safe mode

Was the thermostat replaced?

Not yet I do have one ordered thou. It is on a pontoon that is fresh water only, would that cause the issue ??

 

[MattFL]

Re: Honda 90hp carb engine kicking into safe mode

A bad thermostat can cause overheating. They can go bad regardless of what water they are used in.

 

[o/b tech]

Re: Honda 90hp carb engine kicking into safe mode

There should be two warning lights at the control box or dash. One will be for the engine oil and the other will be a temp light. They should lite up if there is a problem. The next time the horn goes off, check for one of these lights.

 

[jackd1023]

Re: Honda 90hp carb engine kicking into safe mode

Okay, new thermostat, still an alarm at wot, kicks into safe mode, temp light goes on. Back off throttle and out of safe mode and runs fine till WOT....... GRRRRRRRR

 

[MattFL]

Re: Honda 90hp carb engine kicking into safe mode

Hmmm. 2 more thoughts. Make sure the temperature sender is working correctly. I hate throwing parts at something blindly, but depending on the cost it might be cheaper to replace it than to have it checked out by the dealer. Secondly does that motor have a poppet valve in the cooling system?

 

[jackd1023]

Re: Honda 90hp carb engine kicking into safe mode

Yes on Poppit valve cleaned that along with the spring. It is strange thou, the alarm goes off like overheating but if you back off to +-2500 rpm the "green light goes on and acts normal. I dont think if was overheating that it would cool off that fast, it is honestly a matter of seconds, and it is good to go. I have a ohm meter as well as a DVA meter if there is anything I could test.

 

[MattFL]

Re: Honda 90hp carb engine kicking into safe mode

It is certainly possible that the motor is overheating, but has pretty good water flow so the temps come down quickly when you bring the RPM down.

3 more ideas for you:

(1) Revisit the poppit valve. Or maybe remove it briefly just to see if the problem remains. I believe those things are supposed to pop open and allow full water flow at high engine speeds, and maybe that one isn't working properly or isn't opening all the way? Hopefully a Honda mechanic can chime in and say if it's safe to remove it entirely just to test.

(2) Have someone stand at the back of the boat and tell you if it is in fact still pumping water at the moment that it overheats.

(3) Check the factory service manual to see if there's a way to check the temperature sender with an ohm meter or something similar. Maybe there's a procedure where you can put it into some hot water of a known temperature and expect a specific resistance value or something along these lines. Basically some way to validate that it is working properly so that you can rule out a bad temperature sender.