Engine Problems Merc 90

[Tyne 47]

I have got a Mercy 90 on my rib I don?t know its age but I do have the Serial its 3913279. I am having a few problems with it; the guy I got it from showed me a receipt for a full service & new starter motor & impellor, this was all done by a firm in Liverpool (I dont know who).

1st I can?t get the choke to work
2nd when the engine is idling it throws steam out everywhere
3rd Today when I was returning from a fishing trip it started to miss on 1 of the cylinders then lost it completely
4th the starter does not seem to engage propely

 

[Texasmark]

Re: Engine Problems Merc 90

Can't help with year. My '94 up service manual starts with engine s/n's of 0D283222 if US built and 09793577 if Belgium built.

Answers:

Assuming you have a thermostat and that puts you in the 3 cyl (vs 6 cyl) engines.

The engine uses a "fuel enrichment" solenoid which is not a choke but rather increases the fuel to air ratio for starting. Activation is by turning on the key and pushing in. That causes the solenoid to energize (12V on the black/yellow wire to it) and allow pressurized fuel (pressurized by you squeezing the bulb till firm prior to starting) to flow into the 3 carbs. A few seconds of that and movement of the key to START while still pushing in should start the process.

Steam is probably just hot water caused by the thermostat doing it's job. Mine is stamped 120F (starts to open) so the outlet water will be slightly above that temp. I was out about a week ago and the ambient was 60 degrees with high humidity and I had steam coming from my exhaust relief ports at idle. The colder the temp the more pronounced it is.....normal.

Plugs foul out usually at high rpm's . Maybe it's time for 3 new ones.

Engagement of the starter requires a charged battery in good condition (able to furnish 120 amperes to start that engine) and clean/bright/tight connections on the red and black cables, both ends....at the battery and inside the engine, connecting the battery to the engine. If that fails, the solenoid internal terminals could be pitted and a new solenoid would be in order.

HTH

Mark

 

[Tyne 47]

Re: Engine Problems Merc 90

Hi Mark
Mine is a 6 cyl I canot here a solinoide or relay coming in when i pussh the key into the choke position the water temp in the uk is about 14 it also has a problem that when ideling it stops jetting water out of the tel tail

Dave

 

[Laddies]

Re: Engine Problems Merc 90

Tyne, your serial starting with 39 seven digit tells that it's a 6 cyl but Mercury don't list that serial group for a 90HP
You need to take a volt meter and test for voltage on the input lug of the choke solenoid to see if the solenoid is bad or a switch or wire
You got some bad info as your engine has no thermostat so either the w/pump is not working or something is plugged up.
The missing after running the engine with a bad cooling system may have been fatal and may also be why the starter does not turn the engine over well, ck compression

 

[Texasmark]

Re: Engine Problems Merc 90

Incorrect assumption (3 cyl vs 6) based upon lack of adequate information.