Running hot. 1974 Mercruiser 166

[CaptRon66]

I started up the engine for the first time today on a hose. Felt the riser getting hot and then checked temp gauge. It was 195 degrees. Replaced the T-stat (which was already done this month) and restarted the engine. With the engine at idle temp is now at 160 degrees. It used run cooler on the hose at 140 or less. The riser is heating up too. Cant keep my hand on it for more than a couple seconds. Valve cover is cool after running for some time. What is causing this?
The boat is run in salt water. Osco riser is new. Osco manifold 3 yrs old. Entire water pump/impeller replaced over the winter. Also had the engine out of the boat last week to replace the exhaust elbow which contains the flappers. New flappers installed. Ran cool when winterizing last fall. The manifold water passages where the riser bolts up are clear. What do you guys think?

 

[CaptRon66]

Re: Running hot. 1974 Mercruiser 166

It's a Mercruiser 165

 

[Don S]

Re: Running hot. 1974 Mercruiser 166

Was water coming out of the transom shield? (idle relief ports) or the prop?

 

[Don S]

Re: Running hot. 1974 Mercruiser 166

BTW, if you click the

butto under your post, you can edit the text, and if you then hit the "Go advanced" button, you can even edit the title.

 

[CaptRon66]

Re: Running hot. 1974 Mercruiser 166

It's spitting out the relief ports. no flow there. Can feel the exhaust coming through them. The flow out the prop might be a little slow. I'm not sure if it's right. The water coming out is pretty hot too. A little hotter would be uncomfortable.

 

[Don S]

Re: Running hot. 1974 Mercruiser 166

Are you absolutely sure the parts for the pump and the thermostat are installed correctly?
You do have an OEM service manual don't you? Just to make sure it's all put together and working properly?

 

[CaptRon66]

Re: Running hot. 1974 Mercruiser 166

Yes to the oem manual. Been doing doing my pumps/t-stats and neighbors for some years. I doubt I got a gasket wrong on the pump. I could take the lower half off and check the pump for a mistake. Installed a 140 degree t-stat. Impeller was rotated in proper direction. tube lined up when installing halves.

 

[ziggy]

Re: Running hot. 1974 Mercruiser 166

flapper below the rivots? on the down side so they flap open?
used a torque wrench on waterpump fasteners?
sounds like yer rwc, used the proper gasket on the new riser?

 

[CaptRon66]

Re: Running hot. 1974 Mercruiser 166

Hello ziggy. Flappers are below the screws which replaced the rivets. Yep, it will open when the engine runs. Proper riser gasket and placement. Used torque wrench on water pump. I have to admit the first time, I installed the flapper upside down and then realized why it wasn't working....duh,wasn't working because it was backwards. Could a exhaust blockage cause overheating? Engine is idling smooth.

 

[ziggy]

Re: Running hot. 1974 Mercruiser 166

Valve cover is cool after running for some time.

do ya mean manifold?

i guess since it was running cool before R&Rin parts. to me those would be most suspect...

Could a exhaust blockage cause overheating?

yes, i think so. assumin ya mean manifold and not valve cover, that's where i'd lean to. suppose ya could take the water hose off the tstat and see if yer gettin water that far to start with. or maybe a clear hose, see if there's any bubbles in the feed line. keep trying to isolate backwards i'd think....

i don't know, but is three years on a salt water run manifold starting to get questionable? appently ya thought the riser was. guess, i'd think a manifold would just rust thru i suppose, but maybe the flakes of scale off it could clog water passages, maybe.....

 

[Don S]

Re: Running hot. 1974 Mercruiser 166

There has been more than one casting that was defective internally due to core failure in the molding process in the foundry.

 

[CaptRon66]

Re: Running hot. 1974 Mercruiser 166

I'll try the old riser tomorrow. It had been replaced as maintenance. That would be real surprising if that was the problem. Guess I'll check the water pump next. I'd hate to replace that expensive manifold and find out it was something else....like a mistake I made.
Ziggy, The manifold is getting hot too. Valve cover is cool. The engine block doesn't seem excessively hot either. It's the exhaust that's heating up. perhaps I'll try clear hose.
I was thinking about running a second hose to the boat to supply water directly to the t-stat. Can I disconnect the hose to the manifold and clamp a garden hose to it? It would seem there is less chance of flooding the engine doing this since the boat is out of the water. Would this help to isolate the trouble or is it a waste of time?

 

[ziggy]

Re: Running hot. 1974 Mercruiser 166

It's the exhaust that's heating up.

guess that's why i'm inclined to be thinking exhust blockage... this L6 cooling system is as simple as it gets best i can see. water comes from the water pump in the drive. thru the pump, out the pump into the upper to the water hose to the connection thru the gimble houseing and up to the tstat. there, some goes into the manifold, some to the engine w/ tstat open. closed, it'd only go to the manifold (that'd be a straight shot from the water pump impeller right to the manifold then back out thru the manifold). from the manifold it would go into the riser, mix with exhust gas on the down side of the riser (if i read dons post right. a miss casted riser could be defetive, blocked right there), then down the exhust pipe, past the relief ports in the gimble houseing thru the exhust bellows and out the prop hub.
i think i'd 1st see if yer gettin water pumped up from the water pump to the tstat. maybe just disconnect that hose for a moment and see if it's got good flow. assuming yes. then i'd go to feeding water directly to the manifold. seems that if ya'd put the garden hose to the manifold only, that ya ought be able to force water out the prop and relief ports. i'm thinking ya'll see reduced flow in doing that. hopefully heading twds the issue...

maybe check the water pump for proper install. maybe put a clear hose on to see if yer gettin air into the system up at the tstat. from what i understand i suppose there could be another possible. waterpocket cover gasket leak. hot exhust + cooling water exiting right past the water pocket cover. from what i get. if the gasket leaks, hot cooling water and exhust gas can be introdced into the feed thru a leak at the waterpocket cover gasket. that'd warm up yer water + introduce air on the feed side. prior to water ever reaching the tstat..... i'm thining the clear hose idea would revel air bubbles if that was the case.

well, don't know if there's any good ideas there or not, i'm just thinking out loud...... hope it's not a mistake that ya made. i'm gettin ready to have that fear too. i been workin on mine all winter too so don't know if mine cools either (if it don't i'm sure gonna suspect an error by me first).... stupid weather just won't break so i can go see....grrrrrr......

 

[CaptRon66]

Re: Running hot. 1974 Mercruiser 166

A surprising day. Changed the brand new riser,replaced with old and it ran cool. Riser cool to the touch. Temp at 120. Water flow increase out the prop. I can't believe the new riser was faulty. How common is this? Does OEM have the same problem occasionally? Have to get a new riser now. Thank you Don. You too Ziggy.

 

[ziggy]

Re: Running hot. 1974 Mercruiser 166

wow, another bum new parts story. just like bondos glm manifolds, now osco risers....... looks like when buyin new aftermarket parts yer really gonna have to check em out prior to install..... cool ya found yer problem captron...... can ya see what the defect in the part is?

 

[CaptRon66]

Re: Running hot. 1974 Mercruiser 166

I attached a picture of the riser and drew an arrow to problem area. About 2 1/4" down this hole bottoms out. Can't find a space to get a straw through from a wd-40 can. Tried bottom and sides. I covered 2 holes on the gasket flange and blew into the 3rd. It's plugged. Air went through with some resistance.
I hope nothing overheated in the drive like the pump,water pocket or any seals. The drive is going to be pressure tested again. Do you think it would be a good idea to drop the lower?...or pressure check and go?

 

[Coors]

Re: Running hot. 1974 Mercruiser 166

Lacquer thinner has no place on a boat, or on a car-It won't even remove finger- print oil.
Send it back-defective casting.
(use acetone)

 

[CaptRon66]

Re: Running hot. 1974 Mercruiser 166

The picture of the riser was taken on my work bench. It was used to remove the primer from the gasket flange yesterday.

 

[Don S]

Re: Running hot. 1974 Mercruiser 166

Sounds like you found your problem.
With no water you may have damaged the pump housing in the drive, the water pocket cover in the upper gear unit and the seals that seal the tube.
You may have also burned the hoses between the exhaust and the transom exhaust pipe and probably the exhaust shutters.
Absolutely pull the drive and seperate the upper and lower and inspect.

 

[ziggy]

Re: Running hot. 1974 Mercruiser 166

while i like to pressure test my drive, i don't think yer issue is with seals in the drive. i do think ya found yer cooling issue. got a close up of the defect? i'd be more worried about possible scale from the block and manifold pluging up the new riser. the arrow point to the mix area. must be the water outlet of the riser. looks kinda like rusty scale? is it? can ya probe thru it with a awl? or is it really a casting defect as dons suggests?.......