Need Help with 170 boat motor!

[bubba22349]

I'm wondering about the cam timing...as well as the "burn thru hole" mentioned before?

I kind of doubt that cam timing would be off by vary much unless there is a lot of slop in the timing chain. You can see that by watching the distribitor rotor. Set mark on the dampner to TDC than turn the engine backwards stop when rotor starts to move the differance would show how loose chain is. Do you have the stock cam spec's? You could check the cam timing events if your dampner is degreed or with a cam degree wheel and a dial indecator set on rocker arms etc. than compare to opening and closeing events to the cam specs and you will know for sure.

As for the plugs, is the fact of the stumble cause for their wierd colors?

Well the plugs to me show that is quite rich especially on the center cylinders a stumble can be from a vacume leak and being too rich. You could clean the plugs but usually best to just change them you could go a couple ranges hotter too. All inline engines with a carb mounted in center have this problem of unequal fuel distribution. Though yours is much more than normal, one thing you might try is to lower the float level to the min setting. Next I was looking again at picture showing base of the old adapt. and thinking that there could not be much of a gasket seal left with a 3/8 bigger opening. Do you have a picture of your new carb adapters mounting flange, the gasket, and the carb base? Seems this might be an area to check to see how much of a seal there is and if it's a source for a possible vacuum leak. Looked them up and found that they are based on the old Carter downdraft carbs, have worked on those before they can be quite sensitive to vacuum leaks.

 

[Frankenstang]

I'm wondering about the cam timing...

Your's and TJ's comment about valve timing was making me wonder...don't 64 and earlier 170's have solid lifters??(I don't recal if this is your original 179). Did you check for proper valve lash based on your setup. I can't tell from the plug pics, but you mentioned the plugs were more white on one side, so wondering if it's possible you've got too much lash and not receiving full charge to each cylinder.
Good luck!

 

[64 inboard]

It is a solid lift. I have checked the lash and everything is set at .016 when warmed up. The timing I want to check yet is the cam to crankshaft timing. (are the gears timing marks aligned?)

Problem is on the flywheel forward setup,its not easy to get to them.(tranny and rear motor mount are in the way) ... I'm guessing the most accurate way is to work off of TDC of a given cylinder and check the valve movement and flywheel degrees of both the intake and exhaust valves, of the next firing cylinder?

 

[Thad]

"an overflow, back to the intake manifold right below the mount base. If the carb floods, this is supposed to pull the raw gas back into the engine"

I'm good at coming out of left field so here goes.
Hull attitude is different sitting stationary and when underway. Could it be possible that float bowel is overflowing when getting underway as bow lifts and fuel is flooding #3 and #4 cylinders?

 

[Lazy JW]

.......
Hull attitude is different sitting stationary and when underway. Could it be possible that float bowel is overflowing when getting underway as bow lifts and fuel is flooding #3 and #4 cylinders?

Good point Thad. That thing is already headed uphill a fair bit just sitting there. The Ford 300 carby manifolds are built off-kilter to compensate for the engine being installed at an angle

Am I correct in understanding that this is NOT the same carb as was used previously?
Joe

 

[64 inboard]

This carb is not the one I have been using since I bought the boat. It has been replaced a few weeks ago, during this whole process. This carb is an NOS body that has never had fuel in it until now. The guy that built the original carb had it on his shelf. He went thru this body and updated the accelerator pump, etc.


After rebuilding the head, I found the "original" YH would percolate fuel when pumping the throttle, without cranking the engine over. The carb is designed not to pump any fuel unless there is vacuum from the engine cranking. This was done to prevent flooding if the gas pedal was pushed when the motor wasnt turning over.

The angle of the carb is a bit of a concern, but my homemade adapter mocks the angle of the original adapter. Point being, they have run this setup since 1963. I have adjusted the float level from 1/2" to over 5/8"" ...the manual calls for 9/16". We have this carb set around 7/16".

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[Lazy JW]

It is a solid lift. I have checked the lash and everything is set at .016 when warmed up. The timing I want to check yet is the cam to crankshaft timing. (are the gears timing marks aligned?)

Problem is on the flywheel forward setup,its not easy to get to them.(tranny and rear motor mount are in the way) ... I'm guessing the most accurate way is to work off of TDC of a given cylinder and check the valve movement and flywheel degrees of both the intake and exhaust valves, of the next firing cylinder?

I'm sure I'll catch some flak for this from the purists, but here goes anyway :mrgreen:
You can do a quick check by pulling the valve cover, then rotate the engine to about TDC on the tail end of the exhaust stroke/beginning of the intake stroke. Carefully observe the valves, the exhaust will be closing and the intake is already off the seat; when they are both at the same height, look at the TDC marker, it should be really close. If your cam is off by a whole tooth it won't even be close.

This whole thing really has me puzzled; where is Gus Wilson when you really need him?

Assuming that the ignition polarity is correct and properly grounded and also that you are using the same prop, the only thing I can see left is the carb. I was going to suggest choking it under load but you already added fuel via squirt bottle which made things worse.

Does one dare remove the flame arrestor for a test? I have seen engines run better sans air filter, even though the filter was clean (brand new).
Joe

 

[64 inboard]

JW, We had the arrestor off when we tried squirting fuel into the carb.

Hope to get time to check out the "timing" the next night or so.

 

[Lazy JW]

Bleah. I'm running out of ideas here.

One possible way to test for an over-rich condition is to simply turn off the fuel while holding it WOT. I run a chain saw a lot; I don't like to run them too close to piston-burning lean as I don't like buying expensive chain saws, so I run them about halfway between blubbering rich and blubbering lean. Net result: long engine life and a built-in warning when it's about to run out of gas because they pick up a bit of speed just before dying. If this boat engine is running way rich it should pick up a bit of speed just as it runs out of gas. Won't cost much to try.
Joe

 

[64 inboard]

Would love to try a factory Ford 1barrell carb for test..thats probably not going to be easy to find tho....

 

[66 Fastback]

My Mustang had a similar lack of power. Is there a possibility that whatever your timing mark reference for TDC is off a bit or not installed correctly? I don't see what I would recognize as a harmonic balancer, but on the cars the outer ring of the balancer with the TDC timing mark can slip. My timing mark had slipped and using the timing light was useless. I confirmed it had slipped and timed it by ear until I got a replacement balancer. (I guess I could have used a vac gauge to time the car).

As far as the plugs fouling, an MSD box should help. I have them on 3 of my old cars triggered by the points. Points last longer and the plugs burn clean. My car with dual 4 bbl carbs used to foul out plugs in 3000 miles. I have not changed the plugs or points in over 15 years. Granted, the MSD treats the sympton and does not correct the jetting, but the carb is obsolete and parts are tough to come by.
Doug

 

[64 inboard]

Doug,
The timing marks are actually marked in the flywheel. I believe its gotta be pretty close. I've started looking for a "temporary" automotive carb to try on it.

In the mean time, I made a base gasket with a 1 3/8" hole in it, to mount under my SS elbow. Hopefully this will mock the original carb adapter (that had that size hole) that I couldnt use with the new head.


getting to the point of having to try some wierd things....

 

[69.5Mav]

At this point I would suggest getting an air fuel ratio kit or a exgaust gas temperature device or both as your bugget allows. I think you need to see what is happening in the exhaust when you try to go to max power.

 

[fordconvert]

Cant easily measure EGT's on a boat because the exhaust manifold(s) have a water cooling jacket around them. Marine regulators have a thing about surface temps above 120*F in enclosed spaces.

 

[64 inboard]

fordconvert is right on with the egt, the water cooling is why it can run an aluminum exhaust manifold.

Some updates from last weekend...

I put new Autolite 45 plugs in.
Changed the prop froma 12x12 to a 12x10.
Checked fuel pressure at the carb...9psi. when idling.
Made the gasket with the 1 3/8" hole.

Results.. Ran up to 3,000 R's then fell flat on her face, just like before.


Next chance I get ,I would like to install a temporary downdraft carb to eliminate the sidedraft and adapter elbow.

 

[fordconvert]

9 seems sort of high for a carb but I dont know that model specifically. Is there a soft line or valve in the system you can experiment with restricting to see if that changes things?

 

[64 inboard]

9 seems sort of high for a carb but I dont know that model specifically. Is there a soft line or valve in the system you can experiment with restricting to see if that changes things?

9 is high... the original Carter sidedraft was rated for 3 or 4 psi. The rebuilt carb' needle and seat is supposed to be good for 8, so not to far off. I may try a fuel regulator if needed.

I did not run the boat in the water with the FP gauge... the adapter fitting was leaking. I want to get that fixed, so I can see whats happening to the pressure when the engine falls down.

 

[Frankenstang]

If I may re-interrupt here (dont' want to derail your's and TJ's train of thoughts, sounds like he's got some app specific knowledge, although to add IMO I'd try to get your psi back to previous leves/regulator...8&9 is close maybe too close ).

Anyway what I really wanted to point out is if you went from a 1.75" gasket opening to a ~1.375" then you richened? your high end A/F mix right?? Kinda been wondering if you've got more than one problem going here...goes back to the look of those plugs, rich&lean indications maybe? Wondering if one problem might be you're dumping fuel at idle or just too rich somehow at idle (that 9psi is bugging me the more I think about it or carb orientation or other). The second problem possibly being leaning out at higher rpm's ( jetting?...not sure, just plain over carbed? ...just wierd that the smaller gasket opeing make a 1,000rpm jump in accessible power).
Just some thoughts, good luck

 

[64 inboard]

If I may re-interrupt here (dont' want to derail your's and TJ's train of thoughts, sounds like he's got some app specific knowledge, although to add IMO I'd try to get your psi back to previous leves/regulator...8&9 is close maybe too close ).
...just wierd that the smaller gasket opeing make a 1,000rpm jump in accessible power).
Just some thoughts, good luck

I think the main reason for the rpm increase is changing the prop pitch from a 12 down to a 10. This alone would add aprox.400 rpm.

 

[Lazy JW]

..... (that 9psi is bugging me the more I think about it.......

Yup. The easiest way to check that is to simply shut off the fuel supply at WOT.