200HP Yamaha Saltwater Series Heat Alarm Question

[marktore]

I was showing my boat (for sale) the other day and ran it for about 8 minutes with the muffs. I don't know why but I felt like it was starting to overheat just from standing next to it, no alarm sounded. Yesterday I was closing it up for the year and I wanted to run the heavily stabilized fuel through it so I had the muffs on for under 5 minutes and my temp alarm sounded. This is the first time this has ever happened but then again I never run it that long with the muffs.

Two Questions:

1. Could I have damaged anything the day I was showing the boat?

2. Can you run the engine using the wash down hook-up? And if so is it better?

It just seems like it would be mainly because it runs water through the complete engine and not just the water pump.

Thanks Everyone!

Mark

 

[Megabyte]

Big block Yamaha OX66 motors (200, 225, 250 hp models) need a lot of water to keep them cool.
Even in the water, a BBY needs a minimum of 700 rpm (in gear) to keep itself cool.
Below 700 rpm, the water pump doesn't flow enough water and you will eventually get a temp alarm.
In the water, I generally like to keep the tach winking between 700 and 800 rpm if I'm trolling or creek crawling.

That said... when out of the water and running on muffs, you must use muffs with a water inlet on both sides of the motor.
If you have very good water pressure and a large diameter garden hose, you can get away with a Y-connector to supply both sides on a single hose.
If you can swing it, use two hoses to supply maximum volume, and make sure that the muffs are tight to the lower unit with as little leakage as possible.
A bungie helps here.

The hose connection on the lower port side of the motor cowling is only for flushing the block.
It is not meant to be used when running the motor, and should not be used for that purpose.

I doubt that you did any damage as the alarm should have given you enough warning.
However, if it has been longer that 3 years since replacing the water pump, t-stats, and poppit, you're due.

Hope this helps.

 

[mildew2]

I had a Yam. OX66 s.s. 250 on my last Parker and I always used a 55 gal. barrel full of water when I ran it. Like Kevin said the SS need alot of water flow for cooling and I believe if you use this method everytime you won't experiance any overheating at all.
By the way..My Yamaha Saltwater Series 0X66 250 h.p. was the most reliable engine
I have ever owned. Horsepower to weight performance was excellent. Yamaha sure found a winner when they designed that series....

 

[Megabyte]

I had a Yam. OX66 s.s. 250 on my last Parker and I always used a 55 gal. barrel full of water when I ran it. Like Kevin said the SS need alot of water flow for cooling and I believe if you use this method everytime you won't experiance any overheating at all.

By the way..My Yamaha Saltwater Series 0X66 250 h.p. was the most reliable engine I have ever owned.
Horsepower to weight performance was excellent. Yamaha sure found a winner when they designed that series....

I agree.
Good advice. 8)

 

[Parker23]

It also helps to take the plastic grates off of intakes before putting on the muffs, helps to get more water flowing easier I guess.

 

[CaptainJim]

i had similar issues at idle on my 200 HPDI in idle in the water.. at higher RPMs no problems, but idle was doom..I changed the Tstats (which were BAD shame on me) and did the water pump (motor only had one season on water pump) and the water pump plate had a slight groove in it, barely noticeable unless you ran a fingernail across it.

spend the extra $20 and get the whole kit - in my case the impeller was pristine, it was the steel backing plate which was worn.

The water pump kit fixed it. Me and a buddy did it in a parking lot with minimal tools in 30 minutes - once I was shown how easy it was I will NEVER pay a marina to do one again.

 

[Parker 2310]

I agree, even with duel water inlets you need a lot of water to keep her cool. I have the OX66 225 and in order to perform maintenance on her, i purchased a 100 gallon Rubbermaid hard black plastic oval water tank. I got it from a farm feed store and it didn’t cost much as compared to damaging an engine. I keep in out back and use it several time a year for any maintenance and winter storage prep.

 

[SBH2OMan]

Me and a buddy did it in a parking lot with minimal tools in 30 minutes - once I was shown how easy it was I will NEVER pay a marina to do one again.

After looking through the factory manual and researching online, I have a feeling there are a lot of "maintenance items" like this on the OX66 that fall into this category for the reasonably competent backyard mechanic. I'm going to embark on my first project tomorrow with mine (going through and replacing all the fuel system components that are known to cause problems)

I stopped working on my own cars about 15 year ago because suddenly "my time was worth more" but with a boat there is an awful lot to be said for being able to fix it yourself when off shore (or at least know what is wrong)...