2002 90HP Overheating at low RPM

[99yam40]

lowering motor would/could help a motor overheating at high RPM while on plane,
not sure why he lower this motor if it was only overheating at low RPM

but raising it back you will not help his over heating at low idle rpm

[zenoahphobic]

I 'd worry when a mechanic's solution was to lower the engine without any other reason to do so!

[99yam40]

inspect PCV , water pump housing for signs of melting(Make sure cup has not turned restricting opening), gaskets/orings, water pump to tube seal
wear plate, cup, and impeller

something is not allowing enough water to run thru the power head at normal low Idle RPM

[nowakezone]

I just reviewed all my service tickets. Here is the order of the repairs for this issue:
2/29/11 Had a mobile mechanic provide and replace the impeller. $150
3/29/11 Had Yamaha mechanic look for the continuing issue, he said the first mechanic did it wrong. Did the job over again replacing the PCV, installing a new Water Pump repair kit, a new gasket cover. He also suspected that since the motor was mounted on the top holes of the mount - he lowered the motor down one location. $226.72
2/6/2012 Powerhead Replaced - twice (first one was bad after I picked up boat ran poorly) also something called the reed valve assembly $3,746.05
6/27/2014- The same mobile mechanic replaced Water Pump and thermostat using OEM parts I supplied. $150.00
1/10/2017 - New Yamaha dealer - put in to replace the shifter and throttle cables, change lower unit oil and replace separator filter. He said I had bad seal and water was in gear oil. He dropped the lower unit to fix the seals and he took off the water pump and replaced with the same kit I noted in my above comments. He lowered the RPM to standard. $727.62 (Handwritten Shop notes are attached) boat shop notes 1-10-2017.pdf

That last repair caused it to go into alarm right away at that lower RPM. I raised it back to 1000 and kept going. Since then, near the end of the season, it started to go into alarm much easier.

I am doing the next investigation with a Navy ship engineer friend in his driveway. Your ideas on what to look for are most helpful.

[rodbolt17]

the design and engineering works have long been done.
rather than trying things or jacking up the idle I would prefer to test and trouble shoot.
that 90 was in production in that same format since 1998. no issues if all was well.

[pstephens46]

99yam40 I have always had a mechanic change the kits out, but I am planning on doing the next. I can order a new plastic housing for the job. I bought the boat in 2010 and there has never been a time when the overheating issue did not occur.
pstephens46 By two hoses you mean flush on the hose attachment and with the muffs? Never tried running it with the hose attachment off its base. Since I had serval mechanics work on it, I insist on the OEM kit. My guess is that since the housing is not in the case, it may be old. I can order a new housing and see if that fixes it.
<http://www.boats.net/parts/detail/ya...078-02-00.html> isn't that the housing in this kit?

You mentioned overheating during flushing. My
solution for that is to use two hoses, one on flush fitting and other on muffs.

Try a new housing as mentioned. Hell, it's 16 years old.

[panasonic]

I know you said it is hard to work on your engine because of where you live, but if you can find somewhere to do some investigation yourself and have the skills that would be good.

I would remove the Lower unit. Hook a garden hose directly to the water pipe using a hose clamp. With a very bright light look up the leg and slowly turn on the hose and see if the water pipe leaks where it enters the block. I am not sure you will be able to see it, but if it leaking there you may have found the trouble.

Also as the others have said make sure the water pump housing is replaced this time. I suspect you have a leak between the pump and the block.

[rodbolt17]

look at the official Yamaha website. they have a dealer locator function and it will list if they have a master tech.
way back in the day I smoked a pump housing on a brand new 40 force.
started it for the PDI and as I walked fwd they muffs slipped off.
takes about 30 seconds to start the housing damage. that thin stainless liner will glow red hot.
so this brand new 40 got a brand new pump ,not all techs would have mentioned it to the shop owner. I did and did the pump.
any sign of housing melt scraps the housing.
the new housing wont come with the tube seal or the retainer.
if you take it to a dealership that has a master tech odds are high they will have most any cooling system maint part in stock.

[TownsendsFJR1300]

IMO, IF it's the SAME mechanic that's been doing all your work, you may want to find another. It is possible he's missing (or the engine) something.

Preferably a Yamaha trained, Master Tech even better.

[nowakezone]

Thank's everyone, I have a manual but live in a condo where its hard to work on anything. I have parts ordered (I'll go ahead and order a new housing too) and update this thread after they get installed.

[TownsendsFJR1300]

I'd hope the impeller was not installed with the vanes in the wrong direction...

Dunno how well, if at all, it would work.


For the Op, if your somewhat mechanically inclined, pick up a manual. The water pumps aren't really hard to do...

And if you go by the book, you shouldn't have any issues..

[99yam40]

So I should order this part as well and replace?

I would open it up and have a look to see what it looks like to see if it needs a housing.
do you know if the housing was replaced ever when you took it in?
.
So you bought the rig used and it has had a problem all the time you have owned it.
you have no idea what was done to it before you bought it.
the plot thickens

also make sure the rubber grommetis in the plastic housing of the water pump sealing the water tube properly

along with the dampener and holder between the water pump and exhaust on the lower unit while you have the lower off.

was the people working on this a Yamaha shop with trained techs?

[TownsendsFJR1300]

So I should order this part as well and replace?

If it truly overheated (say on the brand new test run for some reason), it could warp that plastic housing. As stated above, that WOULD limit water flow to the powerhead.

It's NEVER been changed so the issue may be following the plastic housing.


BTW, folks (including dealerships) do stupid things (one of my neighbor as well). They crank up the engine with NO water, just for a couple of minutes.
All you need is one new guy to crank it up before you bought (with no water to it)

Guess what you now need...

Also, there usually is a seal at the top of the "water tube" at the powerhead. If that's missing, you loose lots of water, especially at idle.

Cover the basic's...

[zenoahphobic]

Seems your mechanics ain't that good. How many "pumps" did they change without fixing the problem: 5!
You pretty much worked it out, new total pump and check the fit between it and the pipe (corrosion, damage and sealing).

[nowakezone]

So I should order this part as well and replace?