Intake Manifold Bubbles

[smiles16]

I finally got a chance to test my outdrive and fuel line work this weekend. Unfortunately some new minor issues have shown up. I already have some theories on these, but wanted to see what you guys think. All of the symptoms were in the water/under load.

1986 Merc 305 4bbl (230hp) Alpha One Gen 1

Problem 1:

There is a significant difference in the idle RPM between neutral and in gear. Setting the idle at 750 in gear put me at 1100 in neutral. Of course setting the rpm at 750 in neutral put me at about 500 in gear. I should add, I was trying out a 21p prop during this when I should have been running my 19p.

Problem 2:

I noticed little micro bubbles on the intake manifold seam, port side, at idle. These went away after running the boat a while.

Problem 3:

The starbord side manifold was warmer than the port side. Didn't burn me or anything, but noticeable difference. Engine temp was right at 160 the entire time.

Problem 4?:

There was a clicking noise present aft of the starboard side of the engine. Sounded like a spark plug zap (like when your checking for spark).

Notes: I did notice a little drop of water around the base of the riser, so probably going to replace the riser gaskets. Also noticed the engine made a sound like running a car with the intake wide open when in the higher rpms. I chocked this up to the big quadrajet, but thought I should mention it.

So, what do you guys think?

Thanks!

 

[alldodge]

I finally got a chance to test my outdrive and fuel line work this weekend. Unfortunately some new minor issues have shown up. I already have some theories on these, but wanted to see what you guys think. All of the symptoms were in the water/under load.

1986 Merc 305 4bbl (230hp) Alpha One Gen 1

Problem 1:

There is a significant difference in the idle RPM between neutral and in gear. Setting the idle at 750 in gear put me at 1100 in neutral. Of course setting the rpm at 750 in neutral put me at about 500 in gear. I should add, I was trying out a 21p prop during this when I should have been running my 19p.

If the prop is to big this can be part of the issue. The other part is the carb may need a bit more fuel while idling. Kind of a mix, and just get it close, so long as it stays running you should be good

Problem 2:

I noticed little micro bubbles on the intake manifold seam, port side, at idle. These went away after running the boat a while.

Could be it has sealed up, but I would not like seeing that. Did you use a torque wrench installing the intake?

Problem 3:

The starbord side manifold was warmer than the port side. Didn't burn me or anything, but noticeable difference. Engine temp was right at 160 the entire time.

This is normal, water flows the path of least resistance, so it happens. If one side was burning your hand I would give it a second look.

Problem 4?:

There was a clicking noise present aft of the starboard side of the engine. Sounded like a spark plug zap (like when your checking for spark).

My guess would be the exhaust flapper. The older ones have rubber around the edges, and after so must time the rubber falls off.

Notes: I did notice a little drop of water around the base of the riser, so probably going to replace the riser gaskets. Also noticed the engine made a sound like running a car with the intake wide open when in the higher rpms. I chocked this up to the big quadrajet, but thought I should mention it.

So, what do you guys think?

Thanks!

Probably the carb, and replacing the gasket is good, along with checking flatness of the surfaces

 

[smiles16]

Here's a YouTube link of it running on muffs, the carb was dry prior to starting the engine on this vid

https://youtu.be/7il62De9zLo

I did not install the manifold gasket. I recently purchased the boat and am ironing out the quirks. I threw the video link up because it just came to mind that I did notice a bit more steam than I am used to seeing out of other boats.

I plan on doing the old carb cleaner trick first chance this week to verify my "bubbles". On the flapper, is this a must have part? I didn't see any rubber pieces in the exhaust port when I pulled the drive (have seen that before).

 

[alldodge]

Here is the link to your motor
http://www.mercruiserparts.com/200-2-bbl-gm-305-v-81-1985-1986-621

Here is your exhaust flappers (Shutters) item 6
http://www.mercruiserparts.com/bam/subassembly/31721/1077/290

The shutters are good to have because if you stop quick the water try's to go up the exhaust. If they are not there or damaged water can make it to the valves.

If you start having over heat issues it will because you reved the motor to high. The motor should not be run more the around 1500 rpms on muffs. A garden hose cannot supply all the water the motor needs and the impeller will run dry and can be damaged.

 

[smiles16]

Thanks for the link and the advice. I'll admit, I got a little carried away, won't do that again.... first V8 boat and all. So, other than me getting nutty with the throttle, did anything stand out for an experienced ear?

 

[alldodge]

Just a bit of carb idle circuit issue, but this may work it self out. The engine idled ok, but it just didn't come back the same way with each return.

 

[smiles16]

So you agree that jives with a vacuum leak?

 

[alldodge]

So you agree that jives with a vacuum leak?

No, I'm thinking more dirty idle circuits.

 

[smiles16]

Well I think I have my plan of attack then. I'll spray some carb clean around the intake, check for leaks and repair if needed. I'll pull the boot back and look at the exhaust flapper. For the carb, I'll run some berymans through the lines and see if it clears up. If not, rebuild.

Thanks Dodge

 

[Rick Stephens]

I would not bother with the Berrymans step. Just do a carb rebuild and get it right the first time. You are highly unlikely to fix anything spraying carb cleaner through the lines.

 

[smiles16]

Mainly using the carb cleaner to check for intake leaks. I agree rebuild is best, I really only use it once in a while to keep it clean. Although, I've had good luck freeing sticky floats by running it through the tank in the past though.

 

[smiles16]

Update:

Checked for leaks today, no intake leaks I can find.Tried carb cleaner around all areas, then hit it with some soap water and found some tiny bubbles coming from the top edge of the valve cover, so no big deal there.

I did however notice I have a very slight Riser base leak and will be replacing those gaskets (probably where the water came from to make the initial bubbles.

Also discovered the cause for my idle issues, one of the primaries is spitting fuel at idle flooding it out a bit. It was actually bogging and surging quite a bit. So, rebuilding the carb this week.

 

[Rick Stephens]

Update:

So, rebuilding the carb this week.

That's the ticket.

 

[smiles16]

Thought I'd add another update, the clicking noise I was hearing was not the exhaust flappers (I checked) it was the spark plug arcing from the wire boot to the head. Ordered new plugs and wires to fix.

Didn't realize until testing the newly rebuilt carb. This was causing my idle issues, had a misfire on one cylinder

 

[Rick Stephens]

Ya had one snapping away. Gotta keep your fingers away from that, yowee.