J
Jerry Barth
Guest
"I have a 1984 mercruiser 260
"I have a 1984 mercruiser 260 GM version. Motor has about 1500 hrs on it, run in fresh water. I've had the boat 4 years and temp has always run in the low to middle range of the gauge. I noticed on the last run last year before I put it up that it was running slightly hotter than it had before. This year we took it out the first time and couldn't run above about 3200 RPM for longer than a couple of minutes without it running to the top of the guage. At about 3000 RPM we could keep it in about the middle, although hotter than I had ever seen it run in years past. Also, after about 30 minutes of running engine would miss if you tried to run it above 2600 RPM or so (sounded like a fuel thing).
I took it home, changed the T stat and fuel filter. Next time we took it out exactly the same results as the first time.
Today I ran it off the hose and probed around with my infared thermoter.
1) Temp at top of T stat housing stays right at 145
2) Temp of both exhaust elbows 150 or so
3) Right manifold all over temp about 165-170
4) Left manifold (I have the center riser version) Fwd part of manifold 205, center and rear 170
Also some steam coming out of exhaust.
Do you guys think it would be right to assume the left manifold has a blocked passage and is restricting the overall water to the motor? Is this why it overheats as it develops more power but is good at lower speeds?
Could the engine miss be related to the exhaust somehow, maybe the Y valve (it looks like this one has a rotating flapper just below the Y) is getting hot and expanding and restricting the exhaust gas going out? I shouldn't have steam coming out with everything else running normal temps.
Also, if it is the manifold I'm going to replace both the manifold and elbow on that side. Any good brands aftermarket?
Thanks for your help guys. I've run this one by my normal mechanic and he's stumped.
Jerry Barth"
"I have a 1984 mercruiser 260 GM version. Motor has about 1500 hrs on it, run in fresh water. I've had the boat 4 years and temp has always run in the low to middle range of the gauge. I noticed on the last run last year before I put it up that it was running slightly hotter than it had before. This year we took it out the first time and couldn't run above about 3200 RPM for longer than a couple of minutes without it running to the top of the guage. At about 3000 RPM we could keep it in about the middle, although hotter than I had ever seen it run in years past. Also, after about 30 minutes of running engine would miss if you tried to run it above 2600 RPM or so (sounded like a fuel thing).
I took it home, changed the T stat and fuel filter. Next time we took it out exactly the same results as the first time.
Today I ran it off the hose and probed around with my infared thermoter.
1) Temp at top of T stat housing stays right at 145
2) Temp of both exhaust elbows 150 or so
3) Right manifold all over temp about 165-170
4) Left manifold (I have the center riser version) Fwd part of manifold 205, center and rear 170
Also some steam coming out of exhaust.
Do you guys think it would be right to assume the left manifold has a blocked passage and is restricting the overall water to the motor? Is this why it overheats as it develops more power but is good at lower speeds?
Could the engine miss be related to the exhaust somehow, maybe the Y valve (it looks like this one has a rotating flapper just below the Y) is getting hot and expanding and restricting the exhaust gas going out? I shouldn't have steam coming out with everything else running normal temps.
Also, if it is the manifold I'm going to replace both the manifold and elbow on that side. Any good brands aftermarket?
Thanks for your help guys. I've run this one by my normal mechanic and he's stumped.
Jerry Barth"