Omc 175 hp 302 engine

[Dave14200]

I have swapped out the engine on my boat. The engine was an omc 190 hp 302. I put in an omc 175hp 302.

My question is on the valve covers it has the firing order for 175hp and 190hp. If I do the firing order on the 175hp same as the 190hp will the 175hp run?

 

[Scott215]

If they are the same, yes
Firing order should be the same

 

[Ericinmich]

Merc marinized the Ford 302 and sold it in a couple HP versions in the 70s/80s... they were the same engine so same firing order.

 

[Dave14200]

I will look again. Both engines are Ford 302 , but I saw the 175hp has different firing order than the 190hp. The 190hp is a 1977 and the 175hp I was told is a 1978. Could that be the reason the firing order is different?

 

[Scott215]

I thought they were both the same. Except in the mid 80 s it changed with the roller 5.0

 

[Dave14200]

I was told by a friend. That if I use the 190hp firing order that I would be ok. If I want less hp use the 175 hp firing order. That doesn't make sense to me. Can any one tell me if this is true by changing firing order it will determine the hp?

 

[techmitch]

I was told by a friend. That if I use the 190hp firing order that I would be ok. If I want less hp use the 175 hp firing order. That doesn't make sense to me. Can any one tell me if this is true by changing firing order it will determine the hp?

Your friend doesn't know what he is talking about.

 

[Scott215]

Same firing orders

 

[PlayDate]

Could be the valve covers came off a later version. What is on the valve covers? I would check the cast date on the engine as well. The key difference between the two firing orders below is the cam. The easiest way to sort that out is to pull the valve covers and rotate the engine.

 

[techmitch]

I have swapped out the engine on my boat. The engine was an omc 190 hp 302. I put in an omc 175hp 302.

My question is on the valve covers it has the firing order for 175hp and 190hp. If I do the firing order on the 175hp same as the 190hp will the 175hp run?

2nd thought, isn't the firing order embossed on the intake manifold?

 

[PlayDate]

2nd thought, isn't the firing order embossed on the intake manifold?

It used to be but I know small block Fords and the most 302 parts are interchangeable. What's on the valve covers and intake could have come from another engine. The only thing different is the cam, the firing order and the accessories.

 

[techmitch]

It used to be but I know small block Fords and the most 302 parts are interchangeable. What's on the valve covers and intake could have come from another engine. The only thing different is the cam, the firing order and the accessories.

Couldn't agree with you more.
So, we pull all plugs, WOT, spin her over an mark where #1 hits,... the next one that hits after that will denote our firing order.
Oh yea, disable fuel and spark.

 

[Dave14200]

I ended up using the firing order for the 175 hp. It fired up and ran . I put water to it with a garden hose in a port on the side of the out drive. Motor wouldn't start. Pulled a random spark plug #2 cylinder it is wet from water. Any suggestions?

 

[techmitch]

Couldn't agree with you more.
So, we pull all plugs, WOT, spin her over an mark where #1 hits,... the next one that hits after that will denote our firing order.
Oh yea, disable fuel and spark.

I ended up using the firing order for the 175 hp. It fired up and ran . I put water to it with a garden hose in a port on the side of the out drive. Motor wouldn't start. Pulled a random spark plug #2 cylinder it is wet from water. Any suggestions?

Did you do this test? If not, all bet's are off?

Edit: When I say hit's, what I mean is when a piston is at top dead center on compression stroke.
@PlayDate

 

[PlayDate]

Did you do this test? If not, all bet's are off?

Edit: When I say hit's, what I mean is when a piston is at top dead center on compression stroke.
@PlayDate

I agree. I'm not sure why the OP didn't do this simple test. Guessing at the firing order on a car engine just means it will start and not run well. On a boat.....with raw water cooling.....that means valves are open when they shouldn't be and exhaust water will backflow into the engine.

As to the rest of it......I would need to see a video of what happened when he turned the water on. Presuming he was using ear muffs on the drive.....my best guess is that there is a problem with the impeller ......and water just pushed by it and filled the engine. When was the last time the impeller was replaced?

Fortunately it is a low horsepower engine. So it should be okay if the OP pulls all the plugs and puts some WD40 into the cylinders. Since he has to pull the plugs......it is a good time to ensure that you have the correct firing order.

 

[Scott215]

Pull all spark plugs immediately do not hit that key until all the plugs are out then you can diagnose from there

 

[Scott215]

He said he put water to a port on the back of the outdrive so is it an old like OMC drive

 

[Dave14200]

I did.pull the plugs. And blew all the water out of the cylinders. Yes I didn't make a wise decision on validating the firing order. Cylinders 5,6,7,8 were dry ( no water) 1,2,3,4 full of water. Had the manifold welded on the outside but did not see any cracks on the inside. Maybe cracked manifold? I would think if the firing order was off it would have filled both sides not just one.

Would it be better to run the engine with the outdrive in a barrel instead of the hose? Not sure if muffs will work on a Stringer outdrive.

 

[Scott215]

I think the go 2468 1357 down each side

 

[PlayDate]

I did.pull the plugs. And blew all the water out of the cylinders. Yes I didn't make a wise decision on validating the firing order. Cylinders 5,6,7,8 were dry ( no water) 1,2,3,4 full of water. Had the manifold welded on the outside but did not see any cracks on the inside. Maybe cracked manifold? I would think if the firing order was off it would have filled both sides not just one.

Would it be better to run the engine with the outdrive in a barrel instead of the hose? Not sure if muffs will work on a Stringer outdrive.

Maybe a cracked manifold as you suggest especially if it is on only one side. I haven't had much luck in welding cast iron except in emergencies. That sounds like the most likely scenario if the other side was bone dry.

You can always use a barrel. The advantage a barrel has is that the impeller picks up the water and manages the pressure. I'm just concerned that the existing manifold could kill the engine.

What caused the first engine to fail?