98 yamaha 115 overheating

[Kickass]

I have a 98 Saltwater Series V4 115 TRLW, I have replaced the following:
water pump
impeller
thermostats
temp sensors
poppet valve
It still overheats at high RPM's above 3000 RPM
the old mechanic I had pulled one of the head covers to check the water jacket, and said it was clean, he did not pull the other one. Soooo, at this point I believe there are only 2 things left, either the other head is clogged, OR maybe it's my TACH is faulty, BUT, I have not looked into the oil issue.
I can tell you this, though, I am tired of taking my boat to guys that say they can fix something WITHOUT water testing it, seems kinda silly, no?

 

[yamamarinetech40]

Re: 98 yamaha 115 overheating

Seems silly to even talk to someone who would pay someone like that....but it's late and I'm a liitle silly so....why do you say it overheats...because gauge tells you? Have you taken five seconds to put your fingers on top of head and see(with cowling off)? If you can keep your fingers on it for more than three mississippis on both heads then it ain't hot....you could pull lower unit, put hose(not on high 50psi, just a good stream) onto water tube and pull thermostats(first) and see if water comes out....clear if it does....you say still overheats....how did it start...has it always since you had it? Did you mount it on another boat....my crystal ball is in shop....

 

[scottfromoz]

Re: 98 yamaha 115 overheating

If the temp really is up, then how about unbolting the other side's head cover and having a look there (the water gallery holes are very small in parts) and other than that it might require the heads off to look at the water galleries on that side of things. Then there is the exhaust cover to remove and check same under that - although it is not as prone as I understand it to blockage.

Cheers

 

[Kickass]

Re: 98 yamaha 115 overheating

Thanks Scott,
I just saw your thread and believe we have the same problem, I am glad I ran across that, RodBolt is THE Man!

Cheers

 

[Kickass]

Re: 98 yamaha 115 overheating

haha, got the boat back, still overheats, the mechanic i use wants me to bring it back, let him test the brand new temp sensors, and thermostats, FIRST, then put it back in the water at my house and "test" it for a hot head,,,,and would be the water jacket I think they call it, what else could it be?????? You see what I have replaced already,,,
temp sensors
thermostats
water pump/housing
impellor
lower unit serviced
1 head checked out, not the other because the last wrench I used said that if this side was clean the other would be clean also.
it pisses strong, I have the correct prop on it for what is WOT on this motor is 5500, with the prop I have it's 5400 WOT. I NEVER run at WOT, this occurs at about 3500 and above.
1998 Key West Stealth, with the original motor, 98 115 yammy saltwater TRLW
thanks

 

[sschefer]

Re: 98 yamaha 115 overheating

Running too lean will smoke up an engine in a heart beat. Make sure your air/fuel mixtures are correct, you have clean fuel filters and your water/fuel separtor is working correctly. Also make sure you fuel tank vent is clear. That's the list of cheap stuff to fix. If it has a control module get it checked and make sure the timing is correct at all RPM's. If the advance is stuck you can have similar problems.

In otherwords, there's a lot more to look for than just water flow when it comes to overheating an engine. Sounds to me like your wrenches are only looking at cooling problems.