2002 90HP Overheating at low RPM

[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.

[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.

[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.

[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.

[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.

[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.

[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

[zenoahphobic]

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

[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

[rodbolt17]

how many of these mokanicks had school/training certs on the wall???

last thing you wish to do is consult an anganeer.
the reason the design stuff is cause they cant fix stuff.
the anganeer work has long been done and proven.
you do not need to redisign it it simply needs to be correctly diagnosed and repaired.

[99yam40]

do Navy ship engineers design stuff or just work to keep the go system running properly on Navy ships?

[boscoe99]

What we here in the USA call mokaniks the Brits across the pond call engineers.

Now what we here in the states think of engineers are the folks that sit at their desks with slide rules and such designing parts. Or calculating stress levels and such. Paper pushers if you will.

I am not sure if it is really true or not but a British engineer (the design man) told me that over there all wannabe design engineers have to spend time working on stuff in shops. So they will have an appreciation of what a mokanik has to go through working on parts that the design man created. The design man will hopefully feel some pity for what the mokanik has to deal with and design a more user friendly way of putting an assembly together.

Back in the day when I was a mokanik I had to remove a boot strap air turbine from an aeroplane. It was a sumbitch. I thought if the design man had placed the access hole over one inch towards the turbine, or placed the turbine one inch towards the access hole, it would have been a snap. But no! I don't think the design man gave a rats arse about the po mokanik.

[boscoe99]

do Navy ship engineers design stuff or just work to keep the go system running properly on Navy ships?

Mokaniks seem to have been elevated to "technicians". Pay is the same but they get to feel better.

Like your garbage man now being referred to as a "sanitation engineer".

[nowakezone]

I did some more troubleshoot this morning. I ran the motor with the double muffs on and lowered the idle back down to under 1000 RPM. It did not set off the overheat alarm after about 8 minutes but it was definitely hotter to the touch on the head than when the RPM was higher.

I looked all around the engine and as far as I can see there was no water leaking under the cowling anywhere. BUT I noticed that water was coming out of a place on the lower unit that I am not sure it is supposed to. It's on the steering pivot pin part of the lower unit. This only occurred with the engine on the muffs. When I attached a garden hose to the flushing connection, no water came out of that point.IMG_20180123_110855688_HDR.jpg
IMG_20180123_111421410.jpg

I am pulling the lower unit later this week. Please let me know if water is not supposed to exit at that point!

By the way - the friend seems sharp - but we will see

[pstephens46]

I don't think water should be coming out of there while running. Wasn't there another OP recently with this observation? There may be a problem where the tube connects to the pump. The rubber grommet/seal. Now that I look again, seems to be more 2 stroke oil than what might be "normal" in the first pic.