Over heat 3ym30

[MyStrayCat]

Hi all
I have been trying to sort an overheating problem with a yanmar 3YM30.
Symptom: engine runs fine, all day at up to 2500RPM, push a bit more ok, but after 2600 will over heat after approx 10min, turn off, cool down, all fine to run at \> 2500rpm

HISTORY
After purchasing the boat found leak from mixing elbow on port engine, ordered new elbow but when replacing found the heat exchanger had corrosion (small V ) at the bottom of elbow flange, ordered a second hand heat exchanger and replaced along with elbow. Heat exchanger looked good and was flushed by marine engineer.

Steps taken so far
# check inlet filter and clean basket
# check and clan inlet openings in saildrive leg, water flow appears ok at strainer
# check raw water impeller and replace 13 vane with 6 vane - water flow improved
# replace pump belts, shoot of a job
# STILL OVERHEATS
# REPLACED raw water pump with another which had been serviced. Water flow improved again but still exhibits "steam" at higher revs. Had not been run until overheat at this stage.

Suggestions please.......

[TedsMom]

It is my understanding that Yanmar 3 cylinder engines with serial #'s below 6000 (approximately) experienced overheating because of undersized heat exchangers. If anyone else has additional information, please expand on this.

[boatpoker]

Yanmar service advisory attached. Most of the problems described in this advisory apparently didn't show up til' between 250 - 500hrs.

[MyStrayCat]

Originally Posted by boatpoker

Yanmar service advisory attached. Most of the problems described in this advisory apparently didn't show up til' between 250 - 500hrs.

Thanks but this motor S/n 11677, so not sure that this is the problem, also stbd motor ok and similar serial #
How hard to pull the tubes to clean?

[boatpoker]

Originally Posted by MyStrayCat

Thanks but this motor S/n 11677, so not sure that this is the problem, also stbd motor ok and similar serial #
How hard to pull the tubes to clean?

Not hard if you have access. Make sure you have new end cap gaskets before you dismantle.