Mercruiser MIE 255 w/out "Snap"

[leysathcj]

Hi All
My father's Century Resorter (inboard) has a Mercruiser MIE 255 s/n 5522459, from the late 70's. The boat is older but clean and well maintained. Runs fine but seems a little sluggish out of the "hole" which wasn't the case last season. I noticed that she seems to run cool...below 100 degrees. What should the operating temp. be? Could be bad fuel but I'm certain we stabilized last season. I'm thinking thermostat and perhaps fouled plugs due to cool running...but I'm no mechanic. I've located stat housing and seems an easy repair. What are the chances that the temp. guage is inaccurate?

Suggestions and opinions are welcomed.
Thanks in advance.

 

[picklenjim]

Re: Mercruiser MIE 255 w/out "Snap"

If your temp gauge is correct that is way to low.Should be 140-150.You can take out the old one and see if it is in the open position.Some times they can get a small piece of debris stuck in them especially inboards with through hull water pickups.

 

[leysathcj]

Re: Mercruiser MIE 255 w/out "Snap"

If your temp gauge is correct that is way to low.Should be 140-150.You can take out the old one and see if it is in the open position.Some times they can get a small piece of debris stuck in them especially inboards with through hull water pickups.

Thanks, that's what I'll do.
Would this "cool running" affect the plugs? Should they be cleaned?

 

[picklenjim]

Re: Mercruiser MIE 255 w/out "Snap"

Thanks, that's what I'll do.
Would this "cool running" affect the plugs? Should they be cleaned?

It could affect the plugs if it is running so cool that the choke isn't going completely off.That could also make it sluggish.If you can get it to run at the correct temperature it would probably clean the plugs itself.

 

[leysathcj]

Re: Mercruiser MIE 255 w/out "Snap"

Cool. I'll check it out this weekend.
Thanks

 

[Bondo]

Re: Mercruiser MIE 255 w/out "Snap"

Runs fine but seems a little sluggish out of the "hole" which wasn't the case last season.

Ayuh,... That's why you're supposed to do a full, complete Tune Up,+ Service,... Annually....

 

[leysathcj]

Re: Mercruiser MIE 255 w/out "Snap"

Pops has a local shop winterize, store and prep in spring. I noticed lacking performance and low operating temp. when I visited recently. I'm afraid to take it to a shop at this point in the season or we may not see it again until fall.