Mariner 135 - 1997 -V6

[sullmate]

Hi,
I am a new member. This engine has one problem at about 12- 1500 RPM this engine runs hot.( temp gauge approaches 200 degrees.) If I get the boat ( 18 ft. Searay bowrider 1994.) in a plane the temp drops to about 110 degrees. I have a psi gauge that shows good pressure at all operating speeds. The impeller is less than a year old and the boat is used only in fresh lake water.
I have read about thermostats. I have never replaced these. Where are they located and could this be the problem?
Thanks in advance for your help.
Sullmate

 

[JUSTINTIME]

Re: Mariner 135 - 1997 -V6

post serial # please

 

[Chris1956]

Re: Mariner 135 - 1997 -V6

That is a strange problem. Thermostats are on the head, under the telltale hose fittings. How does the motor run at idle (800RPM)? If it overheats at idle speed, you might have a piece of the impeller blade missing, if not you can try changing the thermostats, but I would be surprized if that is the problem. You might replace th poppit valve. It is on the lower starboard part of the motor.

 

[sullmate]

Re: Mariner 135 - 1997 -V6

thanks for your interest. The serial # for this mariner 1997 - 135 is OG541593.
I bought this engine new, it has about 200 hours on it.

 

[sullmate]

Re: Mariner 135 - 1997 -V6

Hi I should give more details.
this engine runs fine at idle, but still runs hot until the boat gets into a plane.
running just off plane (about 2000 rpm) will cause the temp gauge to rise + 200 degrees. The water pressure gauge goes from 3 psi up to about 15 psi at full speed.

 

[Chris1956]

Re: Mariner 135 - 1997 -V6

3 PSI is a bit low at idle. It should be more like 5 PSI. 15 PSI at WOT is normal. Have you changed the prop for more pitch recently, or a different style of prop. Maybe you are a bit overpropped, and it shows as overheating at pre-planing speed.

Did you suck up some sand and rip up the impeller? If so, change the inpeller again. 135HP may be a bit low for a heavy 18 footer. What is the max HP rating on the boat?

 

[sullmate]

Re: Mariner 135 - 1997 -V6

prop is 4 years old 13 7/8 X 21 Stainless. ( good condition) Max HP rating for my searay 18 Ft is 140 HP. Boat turns 5200 RPM at full speed. Top speed is about 52 MPH. I don't think sand is the problem.
I will install a new impeller. Need info on the thermostat ( 1 or 2 ?) and poppet valve.
Thanks

 

[j_martin]

Re: Mariner 135 - 1997 -V6

Check the temp of the tell-tale stream on the hose. (Steal yer wife's electronic kitchen thermometer, but don't tell her.) It should be about 140 degrees. If it's a little cool, it's probably OK, if it's hot, replace the thermostats.

If it's normal, check out the water pump one last time. If there's any scratches in the end plates or housing, replace those also, and the seal between the water pump and the delivery tube.

If yer getting 5200 rpm, prop is about right. Sometimes going down one or 2 inches will let it run a little better, though, especially on a heavy boat. That motor would much rather overrev than lug.

hope it helps
John

 

[sullmate]

Re: Mariner 135 - 1997 -V6

T.Y.
Checked the stream at the pee hole. Temp is right at 140. I have never replaced the thermostat or poppet valve, this is my next replacement. I don't want any problems as this has been a great engine.
Sullmate

 

[JUSTINTIME]

Re: Mariner 135 - 1997 -V6

if you want a manual PM me

 

[gss036]

Re: Mariner 135 - 1997 -V6

Repair the poppet valve, it is probably stuck open.

 

[Chris1956]

Re: Mariner 135 - 1997 -V6

Sulmate, Those RPM and speed numbers do not coorelate. , RPM is too low to create a 52MPH speed. I alos have some experience since I have a Merc 135HPV6 on a light 16' speed boat, with a 21 Pitch SS Rapture. Check the tappet for proper operation.

Do you have a 19" pitch prop to try? If that doesn't make the overheat problem go away, it is likely a bad water pump impeller, gaskets seals etc.

 

[sullmate]

Re: Mariner 135 - 1997 -V6

Chris,speedo shows 55-56 mph, so if i take 10% off speedo for slippage, I should be around 50 ish mph, no? Boat weighs approx 1600 lbs plus 415 lbs for the engine, plus 30 gal built in gas tank. Current prop is 3 blade.
Don't have a 19 inch. This would get engine rpm up to about 5400. Current hole shot is good. I guess the additional rmp might add some top end speed.
I think engine is set low on transom ( in the lowest mounting hole). Engine will not ventilate if trim is in full trim up position.
Your thoughts,
Thanks
Sullmate

 

[sullmate]

Re: Mariner 135 - 1997 -V6

thanks,
I have a Seloc manual. Appreciate your reply. I really like this site and all the good advice!
Sullmate

 

[Chris1956]

Re: Mariner 135 - 1997 -V6

Sullmate, Speedos can be grossly inaccurate. Experience says your is likely reading too high. I would expect no more than 45MPH with that setup. Hawever, back to the topic. Inspect the poppit valve. If that is not it, I am not sure what to advise. Are the water pickup holes partially plugged?

 

[j_martin]

Re: Mariner 135 - 1997 -V6

If your impeller has broken up in the past, or if you ran over some soft stuff, moss, weeds, or a rotten log that got some debris in the water jacket, that would make it act up.

As you rev it up, water pressure should increase till about 3000 rpm, then suddenly drop a small amount (but easily seen) as the poppet valve opens. If it hangs low all the time, you might have something wrong with the poppet.

It's readily accessible, and simple to work on.

hope it helps
John