Overheating

[Diatom]

2011 C26 Yanmar 4BY2-180... cruising temperature has been climbing +1°F/year from 195 to 199.
Suddenly and unprecedentedly crosses 200 topping out at 202 as I progressively drop RPMs and turn on the cabin fans to mitigate. Crawled back to dock.
I note:
■ cabin blowers certainly produced warm air and dropped temperature 1°F, but not so hot as usual.
■ no "mayonnaise" in oil filler cap nor on dipstick
■ no white/black smoke, no unusual noise/vibration
■ usual wet exhaust appearance/volume
■ sea strainer normal, tiny piece of seaweed circling at ~120 RPM.
■ pink bilge (not enough to actuate bilge pumps)
■ pink spray evident under port side mid-engine
■ heat exchanger cap in perfect order, fluid notably low, down 1" or so.
■ heat exchanger fails to draw back coolant from reservoir upon cooling
■ reservoir/cap/tube/fluid in good order
■ 1" hose from mid port engine apparently going forward to water heater (?) has a soft/bloated terminal extension, two clamps not broken but visible gap underside with pink encrustation; this point is above all discernible pink spray.
■ most recent events: two heavy storms recently buffeted boat at dock; left electric power to hot water heater 2 successive nights some days prior to incident (unusual, virtually never use electric heater).

My best absolutely-amateur guess is either
(a) the extension joint in the 1" hose is progressively failing
(b) the thermostat is kaput in partially-closed position, leading to the extension joint letting go.

Shall I dare top up heat exchanger with glycol & crawl 15NM to shop?
Any other ideas/advice?

Thanks -

Diatom

 

[William Sanborn]

Remember you are not spark igniting the fuel, but are heat igniting. Water boils at 212 F, and under pressure is higher than that. The higher heat helps with fuel ignition. Sounds like your inspection is found no major coolant problem. I would take the trip and keep a close eye on the temp and would not be concerned up to 210F. My experience on my sail boat was a Raw Water pump impeller that had one fin still attached and three more loose and caught in an elbow.

 

[Martin610]

Definitely check impeller. When was the last time the heat exchanger was cleaned?

-martin610

 

[jeffhowell1]

I have 2011 R-27 with same Yanmar 4BY2-180 engine

Fill YG30R Coolant to top at engine block cap, not at overflow reservoir
Replace clamps at both ends of hose to overflow reservoir (mine were original wire clamps and leaking under pressure)
Change/clean air filter on regular basis (more often than I thought I needed to)

Owned boat for 4 1/2 years, engine runs great now, after much professional mechanic work app 2 years ago
Turbo replaced after waste gate failure
Heat Exchanger core rebuilt

 

[Diatom]

Thanks for comments. Seized turbo freed & cleaned up earlier this year. Heat exchanger cleaning: highly suspect in respect of annual +1°F cruise-temp climb despite local shop's claim of attention. Impeller - I'm fastidious about replacing the seawater impellor annually; normal flow thru strainer & exhaust (visual). Opened heat exchanger, coolant 1" low, cap in perfect order, takes several top-ups to get stable fill-to-brim. One C26 advantage: simple access to heat exchanger, under cave stairs. Took a boroscope to the port side to see what's going on: looks so simple as the "extension hose" clamps, tightened both clamps. Sailed off to trusted shop, 15NM at 8 knots (using coolant temperature as my guide) with cabin heater on, kept things to 198°F max. I have the feeling I was getting too complicated: the hose joint was leaking, depleting coolant, Yanmar doesn't run happily on low coolant.

I've had 2 different "extension hose" leaks now. I guess the factory? or shops? like to fit a short flexible (and inferior) hose at the end of generic hoses to facilitate tortuous connections. For some reason those connections seem to be particularly prone to working loose.