merc manifold temp question

[chopperpunk]

back again..got the drive...all worked out good there..boats in the water...and it still floats!!...even after the big storm that hit us here in milwaukee today,, anyway...about exhaust manifold temps...i have a 1980 merc 260, in a 26ft century 7000, serial 5376489...went out...got the IR temp gun..and started playing,,,,engine temp great, thermostat is a 140,,at the temp sensor reading 141-146,,, gauge on dash agrees, comes out of the engine at about the same temps...141-146 range,,elbows stay around 110-130 range,,, now the exhaust manifold have local hot spots, i know by the center 2 exhaust ports its going to be a bit warmer...following along the top of the manifold temp ranges from 151-175 180,, , is that a acceptable temp differance on the manifold?, just bought the boat over winter...have not a clue when or if they were ever replaced, ive read 5-7 years max service life,,,the small areas i could see taking the end caps off look great...but i know theres lots more then the eye can see...im sure all this will be answered with...replace them...but i guess i would like someones opinion that has more time with mercs then me....last boat was a OMC...and those manifolds ran COLD!....any help...thanks a million!!...ill get some pics...had a wicked flame job done on tha boat!!...not much good when i just sits at the dock tho!!

 

[jerryjerry05]

Re: merc manifold temp question

The manifolds are gonna run warm.If you are worried change the risers.Or pull them and check the output end for corrosion.Jerry

 

[chopperpunk]

Re: merc manifold temp question

ok update on the temp issue....well had it on the water sunday...idle did ok..temp little over 150 on the gauge,, got up to about 3000rpm and the gauge pegged out over 275, checked the manifolds on shutdown,, exhaust manifolds got up to 375!....intake manifold was around 180, manifolds and elbows are already on the way...would still like a little input on this...the water coming in from the lake is about 55-60 degrees

 

[jerryjerry05]

Re: merc manifold temp question

Sounds like you have the right fix.After you remove the manifolds look in the tubes and see if the flappers are ok and move free.Jerry

 

[chopperpunk]

Re: merc manifold temp question

well the boats in the water right now...and no trailer...can i see those from topside...if not...its prolly gonna be out soon for a lower shift cable...im sure i could see it from the lower side when its out...thanks Jerry...i owe ya a beer or 8 !!...lol

 

[chopperpunk]

Re: merc manifold temp question

ok latest update with the temp issue,, took it out for a ride last night...under 2100rpm temp gauge on the dash shows a touch over 150, hits 2100rpm temp starts to climb,,,back off the throttle to 1800rpm and it cooled down,,, i really hope my restriction is in the risers or the exhaust manifolds...also could the wrong prop cause a overheat issue...it has a 14 1/2 x 17 stainless on it now...that prop was in the boat when i got it...there was no outdrive when i got the boat...got the drive and i figured id give this prop a shot...boats a 1980 Century 7000 26ft.

 

[chopperpunk]

Re: merc manifold temp question

well did the manifolds and elbows, it did make a major differance, yet around 2000rpm and up ...still gets hot,, and as fast as i can pull the throttle back..it cools down, so i went and bought a searay...and thats in the water and running great,, easy fix to the problem, lol. so now i have the outdrive off of the century and going to recheck what the so called tech did for me, no obstructions from the the gimbel forward, last place is in the outdrive, also has new water pump on the engine, new manifolds , elbows, and thermostat,,,if anyone knows something im missed let me know!!..thanks all great help!!...no to go find out why my searay growls in turns!!