Happiness to Dismay - 470 overheating. UPDATE - FIXED !

[Rake722]

Hi guys, I thought I'd start a new thread dedicated to the cause.

After finally getting my 470 on the water, she overheated.

Hit 225 after 20 mins or less.
I cut the engine, let her cool and headed to shore - did not blister paint or get too hot.

The exhaust manifold and riser has been replaced for a new one.
The 3 inch HE has been replaced for a second hand 4 inch.
The exchanger has been rodded and is or was clear.
The impeller has been checked and looks good (was changed 2 months ago)

The flow of water from the transom outlets is low, like a spray.

Local mech said blockage or headgasket blowing into water.

Any troubleshooting steps greatly appreciated.

Where should I start ? replace the impeller and housing (housing was not changed last time but engineer said it was ok)

Many thanks in advance.

Never ending story this engine.

EDIT - For info she seems to overheat in the 3000 rpm and above range, allow to cool she will cruise at low revs at 175 degrees.

Lots of water from the prop when on muffs, only spray from the transom oulet.

Also when leg is in a bucket - noticably less water from outlet than when on muffs - but still nothing compared to my friends alpha 1 outlets...his gush, mine spray.

Hope that helps nail it down.

Ron.

 

[Bondo]

Re: Happiness to Dismay - 470 overheating.

Re: Happiness to Dismay - 470 overheating.

Ayuh,.... 2 things come to mind,... The impeller ain't pumpin', or the riser is plugged up...

Ya need a good flow of raw water comin' In, 'n it's gotta be able to get back Out...

 

[Rake722]

Re: Happiness to Dismay - 470 overheating.

Re: Happiness to Dismay - 470 overheating.

Thanks Bondo.

Riser and mani are brand new never been used till the day it over heated so it can't be that.

I wonder, I changed the old log type for a newer aluminium one. Lookin at the flow diagrams there are some differences.
If I had the raw water pipes inverted in some places would that do it ?

Thinking the raw water pickup goes to the opposite end of the HE that the log type does. Also the in and out of the raw system seem the opposite way around. Am I just clutching at straws ?

Impeller was changed 2 months ago. Visually it looks sound and is pliable. Its not spitting much out though...Didn;t change the housing either....

Is there anyway to rule out the dreaded head gasket at this point? monitor bubble somewhere ?

 

[Bondo]

Re: Happiness to Dismay - 470 overheating.

Re: Happiness to Dismay - 470 overheating.

Didn;t change the housing either....

Ayuh,.... I avoid 470s like P*#^ed off redhead,... Can't say 'bout the plumbin'....

Was there any,.. Any scorin' on the impeller face plates,..??

If so,... Change it out, 'n try it again...

With the raw water line pulled from the exchanger, it oughta pump a good solid flow of water,...

Unhook it, 'n try it... a short run will tell ya if the impeller is workin'... or not,...

 

[Rake722]

Re: Happiness to Dismay - 470 overheating.

Re: Happiness to Dismay - 470 overheating.

Its a long story but that motor was supposed to be a 3.0l then I found out it wasnt but it was too late.

OK will do as you suggest and reconnect as is and check flow from the pickup pipe at the HEx.
Then at the VR, then after the VR and at the Header / riser.

Someone also suggested a kink in the transom area.

A clear pipe to check for bubble from the pickup to the HEx.

Also, how would I check for blockage at the transom outlet / exhaust ?

Thanks

Ron.

 

[stonyloam]

Re: Happiness to Dismay - 470 overheating.

Re: Happiness to Dismay - 470 overheating.

Thanks Bondo.

I wonder, I changed the old log type for a newer aluminium one. Lookin at the flow diagrams there are some differences.
If I had the raw water pipes inverted in some places would that do it ?

Is there any chance that you used the wrong gasket? There are 2 one foe the cast http://www.mercruiserparts.com/showSpecialPicture.asp?pn=856705 and one for the aluminum http://www.mercruiserparts.com/showSpecialPicture.asp?pn=18272

 

[Rake722]

Re: Happiness to Dismay - 470 overheating.

Re: Happiness to Dismay - 470 overheating.

Hi terry

I used the one that came with the kit from mercruiser. Same as in the second of your links

 

[Rake722]

Re: Happiness to Dismay - 470 overheating.

Re: Happiness to Dismay - 470 overheating.

I uploaded these for your review...look ok or shot ?

Thanks in advance.

 

[Rake722]

Re: Happiness to Dismay - 470 overheating.

Re: Happiness to Dismay - 470 overheating.

quick update.
Ran a hose from the VR through the out drive and found a leak at the transom plate water pickup where it connects to the rubber pipe that goes to the water pump.

Need to pull the whole thing and inspect.

Any guides to remove MC-1 pre alpha legs and gimbal housing greatfully recieved.

Thanks.

Ron.

 

[dingdongs]

Re: Happiness to Dismay - 470 overheating.

Re: Happiness to Dismay - 470 overheating.

hi again,thought you had it all sorted once i saw your video but another problem.
drive can be removed similar to alphas by selecting forward undo 6 nuts from drive and pull drive aft.the gimbal housing on my 74 mr drive only has a couple of pins which have to be pulled outwards after removing an alloy style pin that goes through a hole through the centre of the pivoting pin.they're normally quite easy to remove if all has been maintained. hope you can get a clearer view with the pics.pic 4 you may be able to see the small holes where the soft pin is driven through and it will be tabbed on the other side of the gimbal ring so will have to be straightened first before pulling.

 

[Rake722]

Re: Happiness to Dismay - 470 overheating.

Re: Happiness to Dismay - 470 overheating.

Hi dingdongs, thanlks for those pics - very usefull indeed.

Did the job today and found that the jubilee clips on the bellows and pipes were not very tight so did them up - no leak now !

took the bell housing of to insepct and all else is very well so lets hope the leak was the cause of the overheat.

 

[dingdongs]

Re: Happiness to Dismay - 470 overheating.

Re: Happiness to Dismay - 470 overheating.

lets hope your all sorted now.a lot of work involved just because a clamp was left loose but at least your not afraid to get down to the nitty gritty.all the best.
regards steve

 

[Rake722]

Re: Happiness to Dismay - 470 overheating.

Re: Happiness to Dismay - 470 overheating.

Thanks dingdong a, never have been or will be afraid of a spanner.
Love the nitty gritty.

Fingers crossed the loose pipe was the reason for the overheat and that the closed side is dandy.

Will report back when confirmed in the hope it might help someone else in the same boat

 

[Rake722]

470 Overheat FIXED !

470 Overheat FIXED !

Guys with there being so many OH issues with these motors I just thought I'd spread a good word.

My engine is a 1977 470 / 170 2BBL and has been suffering from OH.

The fix was to replace the water pickup pipe between TSOm and Drive. the one fitted was the wrong size and not even tight causing cavitation.

I also replaced the whole waterpump assembly.

We were out for 2 hrs at 3100 revs most of the time and no sign of overheat.,

Video here -

Thankfully I am happy but one issue remains.

Whilst on the water we moored up onto a buoy for some fishing. I could not get the motor to fire up unless the throttle was half way to WOT. Backed off to put in geart - engine dies. Would not idle. Normally will idle at 750 happily.

Had to start her in gear at half throttle to get moving.

Any ideas greatfully recieved.

All in all a happy chap.

 

[ktbarrentine]

Re: 470 Overheat FIXED !

Re: 470 Overheat FIXED !

Sounds like maybe a stuck choke plate?

Your local laws must be different than ones I am used to. Against the law to moor to a bouy. Just sayin'.

 

[Rake722]

Re: Happiness to Dismay - 470 overheating. UPDATE - FIXED !

Thanks for the comment - it was our clubs mooring buoy so all ok on that front.

I had checked the choke operation the other day and saw the plate opening with time so still a bit confused.