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TOPIC: Yamaha outboard overheat

Yamaha outboard overheat 07 Oct 2017 19:05 #1

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I have a 2007 Yamaha T60 outboard that I recently replaced the water pump impeller on due to no stream (peeing). I did a kit replacement and after I completed I ran the motor on muffs. For the first 10 minutes everything looked good, strong pee stream, but at about 12 minutes a heard the alarm buzzer go off indicating over-temp (i have no temp gauge). I then replaced the thermostat (140F) and got the same results when running on muffs at idle. I then took the water pump apart again and verified no obvious problems with my r&r. Put it back together and ran it again and got the same results but this time I used a laser temp gun and monitored the thermostat cover temperature. The thermostat quickly got up to about 140F and then the temp increase slowed down but slowly crept up to about 165F, which is were the alarm triggers. It looked like the temp was going to stabilize at about 165F. I then increased the rpm's slightly (from ~950 to ~1050) and the temp started decreasing until it got to ~135F, which is where it stabilized. So for some reason a slight rpm increase solves my over-temp problem. I don't have a maintenance manual and I can't seem to find anywhere online that tells me what the proper rpm speed should be at idle or how to adjust it. This is a fuel injected motor and computer controlled. And ideas on how to resolve the issue?

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Yamaha outboard overheat 08 Oct 2017 06:28 #2

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I would run it in the water and see how it acts. It could be the muffs were not sealing enough, or maybe not enough flow.
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Yamaha outboard overheat 08 Oct 2017 11:19 #3

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Thanks for the reply.

I did launch the boat (pontoon) and after about 10-15 minutes at idle the alarm went off.

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Yamaha outboard overheat 08 Oct 2017 11:33 #4

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Don.....are you sure the impellor vanes are oriented in the right direction inside the pump? Do you have a strong pee stream at idle? Check the opening for your pickup for any blockage.
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Yamaha outboard overheat 08 Oct 2017 11:51 #5

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FISHIN00 wrote: Don.....are you sure the impellor vanes are oriented in the right direction inside the pump? Do you have a strong pee stream at idle? Check the opening for your pickup for any blockage.


I do have a strong pee stream at idle and I did verify the impeller vanes are oriented correctly. Inlets look good.

With the old water pump I never got a overheat alarm, just no pee stream as I launched.

With the new water pump I only get an alarm at idle. If I bump up the throttle slightly the water cooling system seems to work.

At idle I would expect a hotter engine temp than at higher rpm's. With my laser temp gun the thermostat cover only gets to ~165 when the alarm goes off and the temp was barely increasing at that point. I'm wondering if I have a sensor issue either with the temp sensor or the rpm sensor. The rpm gauge claims it's ~950 at idle but to me (by ear) it seems much lower.

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Yamaha outboard overheat 08 Oct 2017 12:31 #6

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Was the old impeller missing any vanes? If so they may be blocking a.cooling passage in the power head.

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Yamaha outboard overheat 08 Oct 2017 13:14 #7

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Nauti Mike wrote: Was the old impeller missing any vanes? If so they may be blocking a.cooling passage in the power head.


No missing vanes.

Here are my old parts

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Yamaha outboard overheat 08 Oct 2017 13:44 #8

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Douggy wrote:

Nauti Mike wrote: Was the old impeller missing any vanes? If so they may be blocking a.cooling passage in the power head.


No missing vanes.

Here are my old parts


Ok good. Since an increase in rpms results in a decrease of temp you have water starvation for some reason. Inspect the pick up area on the lower unit for marine growth or sand. Sand can also deposited throughout the cooling system but I would start at the pickup area.
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Yamaha outboard overheat 08 Oct 2017 16:05 #9

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Nauti Mike wrote:

Douggy wrote:

Nauti Mike wrote: Was the old impeller missing any vanes? If so they may be blocking a.cooling passage in the power head.


No missing vanes.

Here are my old parts


Ok good. Since an increase in rpms results in a decrease of temp you have water starvation for some reason. Inspect the pick up area on the lower unit for marine growth or sand. Sand can also deposited throughout the cooling system but I would start at the pickup area.


I did inspect (and reinspect) the water pickup inlet and the cavity of the lower unit when I had it apart. No obstructions found.

I performed a power unit flush which is done with the engine off using a garden hose connected to the power unit flush hose/connector. Water flowed through the head passages and out through the lower unit.

I played around with the rpm vs engine temp again and found that I just needed a slight increase in rpm's to get the cooling system to work. So slight that the analog gauge barely moved. I'm starting to think the analog rpm gauge is a pos and not giving me accurate data. I have been wanting to get a digital mutifunction meter that is compatible with my command link system which will provide more accurate and more system data.

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Last Edit: by Douggy.

Yamaha outboard overheat 08 Oct 2017 16:21 #10

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Douggy wrote:

Nauti Mike wrote:

Douggy wrote:

Nauti Mike wrote: Was the old impeller missing any vanes? If so they may be blocking a.cooling passage in the power head.


No missing vanes.

Here are my old parts


Ok good. Since an increase in rpms results in a decrease of temp you have water starvation for some reason. Inspect the pick up area on the lower unit for marine growth or sand. Sand can also deposited throughout the cooling system but I would start at the pickup area.


I did inspect (and reinspect) the water pickup inlet and the cavity of the lower unit when I had it apart. No obstructions found.

I performed a power unit flush which is done with the engine off using a garden hose connected to the power unit flush hose/connector. Water flowed through the head passages and out through the lower unit.

I played around with the rpm vs engine temp again and found that I just needed a slight increase in rpm's to get the cooling system to work. So slight that the analog gauge barely moved. I'm starting to think the analog rpm gauge is a pos and not giving me accurate data. I have been wanting to get a digital mutifunction meter that is compatible with my command link system which will provide more accurate and more system data.


Is all this on a garden hose? If so the pressure might be a little low. Try taking her out to see what happens.

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Yamaha outboard overheat 08 Oct 2017 16:45 #11

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Nauti Mike wrote:

Douggy wrote:

Nauti Mike wrote:

Douggy wrote:

Nauti Mike wrote: Was the old impeller missing any vanes? If so they may be blocking a.cooling passage in the power head.


No missing vanes.

Here are my old parts


Ok good. Since an increase in rpms results in a decrease of temp you have water starvation for some reason. Inspect the pick up area on the lower unit for marine growth or sand. Sand can also deposited throughout the cooling system but I would start at the pickup area.


I did inspect (and reinspect) the water pickup inlet and the cavity of the lower unit when I had it apart. No obstructions found.

I performed a power unit flush which is done with the engine off using a garden hose connected to the power unit flush hose/connector. Water flowed through the head passages and out through the lower unit.

I played around with the rpm vs engine temp again and found that I just needed a slight increase in rpm's to get the cooling system to work. So slight that the analog gauge barely moved. I'm starting to think the analog rpm gauge is a pos and not giving me accurate data. I have been wanting to get a digital mutifunction meter that is compatible with my command link system which will provide more accurate and more system data.


Is all this on a garden hose? If so the pressure might be a little low. Try taking her out to see what happens.


I did take her out after replacing the water pump and thermostat. I thought I had it fixed and packed up the boat with the wife and dog for a day on the water. After I launched and secured the boat to the dock the alarm went off. I think the dog was more bummed out than the wife and I. But at that time I didn't know that increasing the rpm's slightly would make it work so we went back home. Fortunately I live only 10 minutes away from the boat launch ... but I did loose my $5 launch fee.

I have been searching the internet for similar over heating issues with the yamaha outboard. I actually a few threads on forums where someone had the same symptoms I have including not experiencing over heat problems at idle until after replacing the water pump. One person took his boat to the shop and they said nothing was wrong but they did increased the idle and charged him ~$250.

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Last Edit: by Douggy.

Yamaha outboard overheat 08 Oct 2017 20:05 #12

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Douggy wrote:

Nauti Mike wrote:

Douggy wrote:

Nauti Mike wrote:

Douggy wrote:

Nauti Mike wrote: Was the old impeller missing any vanes? If so they may be blocking a.cooling passage in the power head.


No missing vanes.

Here are my old parts


Ok good. Since an increase in rpms results in a decrease of temp you have water starvation for some reason. Inspect the pick up area on the lower unit for marine growth or sand. Sand can also deposited throughout the cooling system but I would start at the pickup area.


I did inspect (and reinspect) the water pickup inlet and the cavity of the lower unit when I had it apart. No obstructions found.

I performed a power unit flush which is done with the engine off using a garden hose connected to the power unit flush hose/connector. Water flowed through the head passages and out through the lower unit.

I played around with the rpm vs engine temp again and found that I just needed a slight increase in rpm's to get the cooling system to work. So slight that the analog gauge barely moved. I'm starting to think the analog rpm gauge is a pos and not giving me accurate data. I have been wanting to get a digital mutifunction meter that is compatible with my command link system which will provide more accurate and more system data.


Is all this on a garden hose? If so the pressure might be a little low. Try taking her out to see what happens.


I did take her out after replacing the water pump and thermostat. I thought I had it fixed and packed up the boat with the wife and dog for a day on the water. After I launched and secured the boat to the dock the alarm went off. I think the dog was more bummed out than the wife and I. But at that time I didn't know that increasing the rpm's slightly would make it work so we went back home. Fortunately I live only 10 minutes away from the boat launch ... but I did loose my $5 launch fee.

I have been searching the internet for similar over heating issues with the yamaha outboard. I actually a few threads on forums where someone had the same symptoms I have including not experiencing over heat problems at idle until after replacing the water pump. One person took his boat to the shop and they said nothing was wrong but they did increased the idle and charged him ~$250.


I would contact Yamaha as they provide good service and stand behind their products.

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Mike
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