Starboard exaust manifold runs hot, while the port exaust manifold stays cool?.???

[TampaBoater]

I have a 1984 Chris Craft Scorpion 215 w/ i/o mercruiser gm alpha one, 5.0L engine.
I had the engine running for about 15mins, the starboard exaust manifold was considerably hot compared to the port manifold. I replaced the thermostat yesterday along with housing gasket. The water impeller is working because there is plenty of water coming out. Any thoughts?

Also, could anyone point me in the right direction in regards to installing an 'overheating alarm'? I am not sure if my boat is equipped, but most likely not.

Thanks,
Les.

 

[alldodge]

Re: Starboard exaust manifold runs hot, while the port exaust manifold stays cool?.??

I have a 1984 Chris Craft Scorpion 215 w/ i/o mercruiser gm alpha one, 5.0L engine.
I had the engine running for about 15mins, the starboard exaust manifold was considerably hot compared to the port manifold. I replaced the thermostat yesterday along with housing gasket. The water impeller is working because there is plenty of water coming out. Any thoughts?

Also, could anyone point me in the right direction in regards to installing an 'overheating alarm'? I am not sure if my boat is equipped, but most likely not.

Thanks,
Les.

Hey Les
I don't think you have an issue. Each side will be a different temps and this is basically because of differences in the amount of water flow each receives. If you put your hand on it and it will not burn you your probably ok. To make sure use an infared temp gauge an test.

So far as the temp alarm you need to have a port available in your thermostat housing so you can install a Temp Switch . You would then run a wire from the temp switch to the ground side of the warning horn/buzzer. You probably have a horn or buzzer so when you turn the key if sounds off until the engine is started and oil pressure increases. Once oil pressure increases the oil pressure switch opens up and removes the ground to the horn/buzzer. Same pricible for the temp switch

 

[Bondo]

Re: Starboard exaust manifold runs hot, while the port exaust manifold stays cool?.??

I had the engine running for about 15mins, the starboard exaust manifold was considerably hot compared to the port manifold.

Ayuh,.... Like AllDodge says, they never run the same, 'n usually, it's the starboard side that runs warmer,...

 

[TampaBoater]

Re: Starboard exaust manifold runs hot, while the port exaust manifold stays cool?.??

AllDodge, Bondo.
Thanks for the re-assurance. I don't have a buzzer right now for the oil pressure because when I crank up, no sounds go off. I do have available fittings on the stat housing so I will be installing a temp alarm. The temp gauge doesn't seem to move up much after engine is warm. All these gauges are factory gagues so I will probably start to replace them soon too.

 

[alldodge]

Re: Starboard exaust manifold runs hot, while the port exaust manifold stays cool?.??

AllDodge, Bondo.
Thanks for the re-assurance. I don't have a buzzer right now for the oil pressure because when I crank up, no sounds go off. I do have available fittings on the stat housing so I will be installing a temp alarm. The temp gauge doesn't seem to move up much after engine is warm. All these gauges are factory gagues so I will probably start to replace them soon too.

Do you have a drive lube bottle with wires coming out of the bottom?

 

[TampaBoater]

Re: Starboard exaust manifold runs hot, while the port exaust manifold stays cool?.??

Do you have a drive lube bottle with wires coming out of the bottom?

ummmm… you lost me there. I should mention that I am pretty new to this whole boating thing. Where would this lube botthe be located at?

 

[alldodge]

Re: Starboard exaust manifold runs hot, while the port exaust manifold stays cool?.??

ummmm… you lost me there. I should mention that I am pretty new to this whole boating thing. Where would this lube botthe be located at?

You might not, if you do it would be on the top starboard side of the engine. I figured if you did have an lube bottle then you may have something which makes a noise or a light shows up if it went t low. Drive lube bottle should sound some kind of alarm if it went empty. If we had your drive serial number we could look it up. Either way it sounds like you know how to wire up a horn

Edit: outdrive serial number

 

[thumpar]

Re: Starboard exaust manifold runs hot, while the port exaust manifold stays cool?.??

A 1984 would not have a buzzer or lube monitor (lube monitor started with gen II). Since you are doing it you could add an oil pressure switch also. They both would run off the same buzzer so its just the price of another switch and a little wire.

 

[TampaBoater]

Re: Starboard exaust manifold runs hot, while the port exaust manifold stays cool?.??

A 1984 would not have a buzzer or lube monitor (lube monitor started with gen II). Since you are doing it you could add an oil pressure switch also. They both would run off the same buzzer so its just the price of another switch and a little wire.

So where would I connect the oil pressure sender? I have a oil pressure gauge but not sure if it works.
Edit: The oil gauge works but it stays arounf 1/4 of the way up, not even half way. The temp gauge also behaves this way.

 

[thumpar]

Re: Starboard exaust manifold runs hot, while the port exaust manifold stays cool?.??

It is a switch not a sender. I think it is in the same location as the switch for the dumbie light in a vehicle.

 

[alldodge]

Re: Starboard exaust manifold runs hot, while the port exaust manifold stays cool?.??

So where would I connect the oil pressure sender? I have a oil pressure gauge but not sure if it works.
Edit: The oil gauge works but it stays arounf 1/4 of the way up, not even half way. The temp gauge also behaves this way.

With your gauge reading only about 1/4 up tells me this could be weak oil pressure but most likely it is either a bad sender or gauge not reading properly. Either the gauge or the oil pressure sender is not an issue so long as you know the status of your engine. To find out what your oil pressure really reads is, install a mechanical gauge in place of your sender temporarily. After obtaining the actually reading you can then decide if knowing what the reading equates to your gauge is good enough or you need to do something else.

If you want to install an alarm as with the temp switch you will need to remove your current oil pressure sender, then install a tee and reinstall your sender and a new pressure switch. Both temp over heat and oil pressure drop are two good things to be notified of if your running down the water. Not having something noisy to tell you something is going on allows enough time for the engine to be damaged before you notice.

As before get a horn and run a 12V lead to one side and run other leads off the other side to the oil pressure switch and temp switch. If either one causes a ground it will sound the horn

 

[TampaBoater]

Re: Starboard exaust manifold runs hot, while the port exaust manifold stays cool?.??

Where would my oil sender be located?

 

[tazrig]

Re: Starboard exaust manifold runs hot, while the port exaust manifold stays cool?.??

Looking at the front of the motor it should be on your left towards the front of the motor. Here is a link to a PDF factory service manu@l for your engine:

Boatinfo - Mercruiser Service Manual nr. 3 - 1978-1984 - All 4 cylinders, L6 & V8 Engines

And for your Alpha drive:

Boatinfo - Mercruiser Service Manual nr. 6 - 1983-1990 - R, MR, Alpha One & Alpha One SS Sterndrives

I'd suggest you bookmark both so you'll have them for easy reference. If you want to spend for hard copies you can call Mercruiser direct at 920-929-5110

If you flip to page 325 of the engine manu@l at the top it has a picture it has a picture of the oil pressure sender so you'll know what you are looking for.

 

[thumpar]

Re: Starboard exaust manifold runs hot, while the port exaust manifold stays cool?.??

And just to add a tip on the boatinfo manuals. When you click on the link you will see there is a /0 at the end. That is the page number. change it to /325 to get to page 325 without having to click the button that much.

 

[MarkSee]

Re: Starboard exaust manifold runs hot, while the port exaust manifold stays cool?.??

How do the elbows/risers, that sit on top of the exhaust manifold feel when you put your hand on those while the boat is running?

Much of a difference in temperature there and can you keep you hand on there for an extended period of time or do you need to remove your hand because the elbow/riser is too hot?

Mark

 

[TampaBoater]

Re: Starboard exaust manifold runs hot, while the port exaust manifold stays cool?.??

How do the elbows/risers, that sit on top of the exhaust manifold feel when you put your hand on those while the boat is running?

Much of a difference in temperature there and can you keep you hand on there for an extended period of time or do you need to remove your hand because the elbow/riser is too hot?

Mark

Yes Mark, the port manifold riser/elbow is relatively warm, and i can put my hand on it for a while, but the starboard riser is much hotter, I can put my hand only for just a few seconds and then I have to remove it.

 

[tazrig]

Re: Starboard exaust manifold runs hot, while the port exaust manifold stays cool?.??

Yes Mark, the port manifold riser/elbow is relatively warm, and i can put my hand on it for a while, but the starboard riser is much hotter, I can put my hand only for just a few seconds and then I have to remove it.

Sounds like you need to pull the starboard riser and inspect for rust. I think you will find it is full of rust and needs to be replaced as it is restricting water flow and is or will be shortly causing an overheat situation. Risers as with Manifolds should always be replaced in pairs.

 

[MarkSee]

Re: Starboard exaust manifold runs hot, while the port exaust manifold stays cool?.??

Yep, based upon what you're finding with the "hand on riser" test, the starboard riser is probably mostly restricted like tazrig indicated but the port is not all that much better if you still can not keep your hand on it.

Mark

 

[agallant80]

Re: Starboard exaust manifold runs hot, while the port exaust manifold stays cool?.??

My boat does this. If I put her in neutral and rev her a bit they both become the same temp. Figured it was not a big deal.

 

[Fishermark]

Re: Starboard exaust manifold runs hot, while the port exaust manifold stays cool?.??

The difference is magnified when running on muffs as there is no restriction for the water. When it the water, there is a bit more restriction and the water has time to fill and run out of both sides.