Overheating Alarm Reduced RPM

[haleyhead]

My 1999 115 Yamaha overheat alarm is going off and the motor is dropping to safe RPM's after about 3 to 4 minutes of running. Is it possible that the heat sensor(s) is bad? I was told that there may be some blockage or scale buildup where the water runs through the head. Is there any way to check this without disassimbling the head? I have a strong flow out of the pizzer. Thanks

 

[Labarb28]

Re: Overheating Alarm Reduced RPM

I had the same problem as you when running greater than 4500 rpm. My motor is a 2000 115. I too had good flow from the pizzer. You will need to pull the water jacket covers and heads to fix the problem. Approx $300 in parts and 6 hours to do this properly by yourself (that's what it took for me). Dealer/mechanic is going to cost you somewhere between $900 and $1000 if the motor comes apart easily. I replaced the head gaskets, water jacket cover gaskets, thermostats & gaskets in addition to the poppet gasket and spring. Turns full throttle now with no overheat problems. The heads/jacket covers will need to be cleaned as well. I ended up soaking them in hot water with a good dose of Cascade dishwashing detergent, then using a plastic scraper and orangewood sticks, scraping out the crud. It took about three different times soaking for about one hour apiece to get the majoriy of it out. This was recommended by another board and seemed to work well.

 

[Fl_Richard]

Re: Overheating Alarm Reduced RPM

I used a 3000 psi pressure cleaner. It litterally blew the scale out of them. It was a messy job but I ended up doing two '01 motors in about 5 hours.

The water jackets around the sleeves were pretty clean. All my effort was with the heads and water covers on the heads.

Same result no overheating anymore.

Rodbolt do you know the WOT rpm for a 200 YammyOx? I get 4600 - this is considered lugging for my JohnyRudes.

 

[rodbolt]

Re: Overheating Alarm Reduced RPM

that 200 OX66 should tap 5300-5500 any time you wish.
if it wont something is wrong.
for cleaning the scale, dont scratch the gasket surfaces, be prepared to get nasty, just get it clean.
and yes it happens with all outboards eventually.
on the OX66 motor, start your own thread and it can be disscussed further.

 

[haleyhead]

Re: Overheating Alarm Reduced RPM

Thanks to everyone. I'll start working on it. I certainly won't take my boat back to our local boat repair pirates. A couple of questions. I have no idea what I'm going to be looking at when I take the heads off. What is a water jacket, Poppet gasket and spring? It sound as if the heads aren't going to be easy to remove. Is that the case? It's a Saltwater series, so most of the hardware is stainless. And, when this all goes back together (hopefully) are the head bolts suppose to be torqued at a specific ft. lb.? thanks

 

[rodbolt]

Re: Overheating Alarm Reduced RPM

FIRST thing YOU need to do is OBTAIN the factory Yamaha service manual from a yamaha dealer.
then READ the section on cyl head removal and instllation.
FIRST tool any tech or wrench turner needs to sharpen is the one on the neck slightly above the shoulders and usually between the ears.
once THAT tool is sharp let the operation began.
the net is great and we can assist with any questions you have about service manual procedures but in the end your the one with a wrench in hand and if your careful this isnt hard.
if your not it can destroy a decent engine.

 

[FISHUNTR]

Re: Overheating Alarm Reduced RPM

Here are a few pics I took when I did my 97 yam 115. This is before & after of the area around the cylinders:

Here is what the inside of the WJ cover looked like along with the Gasket:

Here is an after pic of the head and WJ cover (forgot to take a before pic of the head):

The job was a real pain in some areas but not near as bad as I was expecting, just take your time. Sure saved a butt load of cash doing it myself.

 

[haleyhead]

Re: Overheating Alarm Reduced RPM

All the advice is fantastic. I really appreciate the pictures and I'll make sure the sharpest tool in the shed is in the tool box... I'm not looking forward to buying a yammy manual from my local boat repair pirates. Maybe they have it at West Marine.

 

[Haffiman]

Re: Overheating Alarm Reduced RPM

Start by checking your thermostats.
They have a nasty habit of failing in closed position (not opening).

 

[rodbolt]

Re: Overheating Alarm Reduced RPM

if your gonna buy it from west simply order it from Iboats. both sell the same NON factory manual. nothing against non factory manuals but,especially for someone who is sure, they can get confusing as they tend to cover 10-20 models between the cover jackets.
if your not paying attention its easy to get in the wrong section.
however the seloc and clymer manuals have notes and tips that the factory Yamaha manal does not.
for what your doing, a simple head removal, the ones iboats sells will work very well.
actually probably better than the factory one.

 

[99yam40]

Re: Overheating Alarm Reduced RPM

I second the checking the thermostats and other parts of the cooling system to make sure they are working properly before pulling heads.
Of coarse the manual would help in doing that also

 

[FISHUNTR]

Re: Overheating Alarm Reduced RPM

Could be this could be that, test this test that.... don't get me wrong the recomendations are sound (motor mechs, please don't take offense), but If you depend on the use your boat like I do, you really want to have peace of mind that when you're done.... you're done and it will work right the first time and for a long time after. Might I suggest you do what I did... replace everything. I think I had 300.00 give or take in EVERY part needed to replace everything in the entire cooling system and clean the water jackets. So now I know it should be fine for a very long time. I would have hated to replace or repair one part or area, get it back together and it breakdown while I'm on a fishing trip etc., then I'd have more down time / missed boating trips till I could get it figured out.

 

[99yam40]

Re: Overheating Alarm Reduced RPM

Throwing parts at a problem and hoping it will fix it gets expensive and you do not know what caused the problem to start out with and what is needed to fix it.

by testing you can at least understand what the problem was and what is needed to fix it properly.Then you can put all the parts you want into the motor just to have peace of mind.

If you do the normal maintenance as Yamaha recommends there should not be a problem with the parts normally, but there is always exceptions to that.

Without knowing when and if anything has ever been replaced it is a good idea to let the owner know what to look at to start out with before tearing open the motor.