yamaha f100 oveaheating problem

Salty-Cs · Posted: Sun Dec 30, 2007 1:43 pm Post subject: yamaha f100 oveaheating problem

This has probably been covered but I had little success when searching. My 2002 F100 has just started overheating at idle but seems OK when cruising. The pee stream is a little weak as well (both at idle and cruise). It is anemic when running in the water or when attached to the hose for flushing. Under the engine cover there is a housing on the starboard side of the engine where the pee stream hose exits...when attached to the flushing hose, water to this housing has excellent pressure but it is weak when leaving the housing where the exit hose to the pee stream is attached. I don't know if this has any bearing on the overheating problem...may just be a side issue. It would seem to me that if the impeller was the culprit the pee stream would be weak with the boat in the water but fine when attached to the flushing hose.

We are in Catalina for New Year's Eve (not a bad place to be marooned) so I am limited to in the water repairs. Any suggestions for troubleshooting this problem while moored would be greatly appreciated...vessel assist would be a last resort if we wind up stranded in mid channel. THANKS!

Dora~Jean · Posted: Sun Dec 30, 2007 1:56 pm Post subject:

Hi Sam (and Kerry), sorry our schedules didn't line up, I just got BACK from Catalina 2 days ago, albeit the 'wrong' end of the island...

Have you ever had the water pump impeller changed? If not, that's the first thing I'd do because while you're at it (or the mechanic) they can check the condition of the pump housing, water tube and many other components for corrosion. I believe it's probably your impeller, because at idle the engine relies completely on that pump, but while underway (fast) the water is forced into the system so the pump doesn't need to be working well to provide cooling.

How do you know it's overheating, do you have a head temp gauge? Or is the overheat alarm sounding?

I'd say unless you're severely overheating in minutes while idling, you'll make it back OK while running. Is that marine repair place open in the winter there at the Isthmus? They might be able to change out the impeller for you, but anything deeper will probably mean your stay will be extended...

fordracerguy · Joined: 06 Mar 2007 Posts: 2

Hello Dora~Jean. This is Chris, Sams son-in-law. Thanks for the info! This looks like a easy fix. Between the two of us we are pretty good at fixing things, as long as beer isn't involved. Smile

Just Kidding.

Salty-Cs · Posted: Sun Dec 30, 2007 2:35 pm Post subject:

Hi Steve,

Thanks for the suggestion...the only way I am made aware of overheating is via the alarm...only happens at idle. Wouldn't the pee stream be strong when using a flushing hose if the impeller was at fault?

Sorry we missed you at the island.

tsturm · Posted: Sun Dec 30, 2007 4:14 pm Post subject:

Dora~Jean · Posted: Sun Dec 30, 2007 4:56 pm Post subject:

Hi again Sam, Kerry and Chris (whoa, the list is getting long...),

When you say attaching the flushing hose, do mean to the flush attachment hose fitting or thru mouse ears on the lower end? Either case, there's a good possibility that you have an obstruction in the system as well (like tsturm suggested with the T-stat gasket), or might be one of the impeller blades has broken off.

Carefully inspect the impeller for any missing pieces, then FIND IT! Whether or not the impeller is in good shape doesn't have much if any bearing on the strength of the pee stream using the flush attachment, but an obstruction would.

Good luck, wish I was there with you guys, we'd crack open some chillable red (after fixing the problem that is). Laughing

Salty-Cs · Posted: Mon Dec 31, 2007 11:05 am Post subject:

Thank y'all for the excellent advice. I ran into an island mechanic yesterday and his diiagnosis concurrs. He seems to think the thermostat the most likely culprit with the impeller quite possibly a factor as well...the former being a much easier repair job. (by the way Steve the built in hose bib flushing attachment was used) I think we will attempt the return trip at a relaxed pace (what else is there on a C-Dory) and start with the less daunting thermostat replacement when we get home.