Mercury 150 (1988) Overheats in idle, even with new Impeller

[Mike D Cincy]

I am stumped. We had the impeller replaced on this outboard, and the engine will not spit out a good stream of water while idling or running with no wake, and it gets hot in a hurry. So it limits the boat usage in no wake zones. Any thoughts?

 

[3car]

Re: Mercury 150 (1988) Overheats in idle, even with new Impeller

well, that motor gets its tell-tale water from the discharge side or the thermostats, so the water will quickly get very hot to the touch. the stream will also vary as the stats open and close, and with rpm.

 

[Mike D Cincy]

Re: Mercury 150 (1988) Overheats in idle, even with new Impeller

Do you think I should replace the T-stats, and if so are they hard to get to and replace?

 

[Silvertip]

Re: Mercury 150 (1988) Overheats in idle, even with new Impeller

Yes -- replace them and No -- they are not difficult to find and replace.

 

[fishingdan]

Re: Mercury 150 (1988) Overheats in idle, even with new Impeller

T-stats are also fairly inexpensive.

How do you know the engine is hot? Are you hearing an alarm or do you have a temp gauge. That era 150v6 will rarely have a strong tell-tale stream due to its design.

 

[andy6374]

Re: Mercury 150 (1988) Overheats in idle, even with new Impeller

Yep replace the tstats.

If you are overheating at idle still, it's likely that your poppet isn't seating properly. This will cause water to exit the block prematurely and you'll overheat...in fact the block won't even fill at idle if the poppet is open.

Also check the hose that is routed to the tell tale. Pull it off and take a look inside. Alot of bugs like to make their home there and then end up clogging the hose up.

 

[Mike D Cincy]

Re: Mercury 150 (1988) Overheats in idle, even with new Impeller

Yes I have an alarm, along with a temp gauge, so the alarm goes off, and of course the gauge is reading hot.

I was able to find the thermostats, and went out and bought new ones. Looks like an easy fix, and well worth the $25. So I will give that a try first.

I take it the poppet is a little bit harder to get to?

 

[3car]

Re: Mercury 150 (1988) Overheats in idle, even with new Impeller

Yes I have an alarm, along with a temp gauge, so the alarm goes off, and of course the gauge is reading hot.

I was able to find the thermostats, and went out and bought new ones. Looks like an easy fix, and well worth the $25. So I will give that a try first.

I take it the poppet is a little bit harder to get to?

very easy to get to. go to
http://www.mercurypartsexpress.com and put in your serial number for an exploded diagram. its under relief valve system.

 

[Mike D Cincy]

Re: Mercury 150 (1988) Overheats in idle, even with new Impeller

Thanks for the info. It's amazing what one word like poppet can do when researching. Very helpful.

I did read where it is possible to loose some parts into the motor when working on this. Given that I am not an expert mechanic, and I cannot find this repair in the Seloc book, are there steps I should take when replacing the poppet assembly?

 

[Windykid]

Re: Mercury 150 (1988) Overheats in idle, even with new Impeller

Just remove in order, clean, check for serviceability, and replace in order. If you still overheat after that your water tube seals are probably worn out.

 

[gss036]

Re: Mercury 150 (1988) Overheats in idle, even with new Impeller

Remove the lower cowling to give easier access to the poppit assy. There are 4 small cap screws that hold it together, nothing to disconnet. About $30 for the complete parts need to replace. The only part to really worry about loosing into the block is the grommet, so if you are aware of that going into it you will "more" careful as you take it apart. It is spring loaded but will not jump out at you.