1998 60 hp precision blend RPM/Overheating issue?

[JamesB86]

Hi, Im new to this forum and not used forums before but hoping to be able to find some advice

I recently purchased and installed a 95-96 60hp precision blend on my runabout.

Before taking the kids out or for a major fish I decided to take it for a run down a local river and out in to the estuary to make sure it was working ok.

First thing I noticed was that the rev gauge wasn't reading but thought that its likely been wired incorrectly.

The motor ran fine until I reached the estuary where I cruised at about 30kph (I can only provide speed not revs) for a few minutes and it was running fine so I opened up to full throttle and it peaked at about 54kph for approximately 20-30 seconds before a sudden RPM reduction and it dropped down to a steady 20kph.

If I turned the motor off for a minute or two and ran it again the same thing would happen, It would happily climb to 54kph for aprox 30 seconds before reducing RPH and speed to 20kph and no more. It wasn't spluttering or erratic it just maintained revs and speed as if it had reduced itself to a safe/overheat mode.

I took it back to the mechanic that installed the motor and I was told that id likely picked something up (weed) around the prop causing it to overheat. They said that they had taken it to the estuary and tested it whilst on the trailer and was working fine. but unable to determine why the RPM guage wasn't working.

I took it out the next morning in the ocean and after a minute opened up to full throttle and it did the exact same thing again. If I let it idle for a few minutes it would allow me to do the same thing but every time the RMP (even though my gauge isn't working im going of sound) would reduce to the same RPM and idle there.

The mechanic is unsure as to why it is overheating or going in to safe mode but I wondered if it could be related to the RPM gauge incorrectly wired or whether its likely a genuine overheating issue.

Other things ive checked is that the oil is full, battery and terminals are near new and its meant to have had a service before installation so im assuming the carby etc is clean.

Any advice would be appreciated.

[TownsendsFJR1300]

If you could, if possible post the actual model # it would help.

Being the boat / motor is new to you, do you know the service history of the engine (receipts)?

Unless you have receipts, etc, I would definitely change out the water pump in any case.

It sounds like its overheating, either from lack of water or possible broken impeller jambed up in the power-head( Not common, but it does happen). Pay attention to the stainless steel WP cup "housing". If it shows ANY SIGNS or OVERHEATING/WARPING , etc, change it. Use an entire WP kit. Its not much more expensive and you get to do it just once..

Most importantly, make sure ALL of the impeller is there, there are no small pieces missing..


The RPM gauge shouldn't have anything to do with your shut down issue.

[ausnoelm]

Very typical blocked water passages symptoms.

[JamesB86]

Ok thank you I will definitely look in to the water pump and impeller. I'm not overly mechanically minded but if it was either of those issues would I not loose the steady stream of water and would it not be warm water coming out?
I'm not sure on the model number as I won't be able to get to the boat till Wednesday (working) but I've spent hours trying to find the 95-96 60hp precision blend model online and can only find the 70hp. Unfortunately I don't know too much about the history of the motor.

[rodbolt17]

typically RPM reduction is fairly violent. means the motor is going to drop back to about 2500 RPM and shake like mad.

any event that triggers RPM reduction also triggers the audible alarm.
make sure the audible works.

think mon think.

if you actually overheated it, that's a lot of metal to cool down.

overtemp switch closes about 183*F.
wont open again until it cools back to about 165*F.
that's a lot of metal to cool.
part of the motor installation is to make sure the tach and the warning system works correctly.

[99yam40]

I agree you need to make sure it is getting an overheat or not.
Make sure your buzzer works. and that the tach indicators for overheat and low oil function properly

If it is overheat,water pump kit with housing inspection and thermostat are the 1st things to look at any time overheat occurs.

While lower unit is off and stat is out hook up water hose to water tube heading to power head and flush it out real good looking for anything that comes out.
Inspect the passages behind the stat for build up as that may indicate what the others look like inside.
If still overheating then pulling head and exhaust covers may be needed to clean passages up.

There are cleaners you can try to clean passages with without taking apart the motor.
research Rydlyme

[TownsendsFJR1300]

There are cleaners you can try to clean passages with without taking apart the motor. research Rydlyme

If needed;

http://www.yamahaoutboardparts.com/f...g-th19434.html

http://www.yamahaoutboardparts.com/f...m-th23666.html