Mercury 90 hp EFI-Alarm sounding and no power

Charter Tofino

Well-Known Member
I just got a call from the parents who were out in the boat. They were driving at low speeds when the engine alarm went off and they lost all power. I quickly told them how to get the kicker (which i almost ran dry yesterday) going and they were close to the marina so they luckily made it in. Figures the only time the boat has problems is when im away and they are using it.

From what i understand -the alarm was constant
-the engine had no power even at low rpm
-they did not know if the engine was pissing


Any ideas on what it might be? I figure its overheating from a bad impeller, the cooling intake is clogged, or the thermostat has a problem.
 
Hopefully a piece of plastic clogged the intake and it's gone now.
Have you tried to start it again?
 
Im not in town and they hauled the boat before i could ask them to check a few things. They mentioned they were in shallow water with alot of seaweed at the time. I asked if they could have hit bottom and they said not likely but ill get them to check the prop.
 
sounds like the high temp alarm. When the computer sets off the temp alarm it also will control the motor power and rpm to prevent any major damage.
 
Are most temp alarm problems are a relatively easy fix? Clogged intake would fix itself. I would imagine a Thermostat issue or bad impeller wouldnt cost an arm and a leg. Are there other common overheating causes im missing? Thanks for the help guys. Im pretty clueless with motors.
 
Had that happend With my merc. Kelp was blocking the water inlet. Run the engine on land and check for the pee stream.
 
Had that a few times with my E-TECS and was weeds. Reverse thrust a couple of times and idle to allow temp drop and everything is fine.
 
Constant alarm is overheat, intermitent is oil. My overheat alarm would always go off at low speed,had my mechanic replace both thermostats and impellar.Turned out one of my thermostats was corroded shut and my impellar was on its last legs,pretty cheap too $240 parts and labour
 
Invest in a water pressure gauge. It will save you from possible gasket failures due to overheating. Way better to catch a clogged water intake well before the alarm goes off. When the alarm goes off, the engine has already heated up beyond normal operating temps and some damage is possible.
 
So they got seawead over top of the intake that raised the temp. which sounded the alarm and burnt up the impeller. If the housing is fxxked they really over heated the motor and ignored the alarm. That is if the alarm worked properly.

That sucks though.
 
Ya they mentioned when it happened they were going through a pile of seaweed so I think that's exactly what happened. The alarm went off and the motor disengaged right away so it likely just fried the impeller before causing furthur damage. 180$ fix so it could be worse. The mercs been surprisingly great. It has the yamaha power head but idles much louder.
 
On my Yamaha there is a plug on the top of each head. Remove it and get a hose fitting with the same thread from a industrial parts supplier.
 
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