Need Help with 170 boat motor!

Lazy JW":3oggbek2 said:
Yup. The easiest way to check that is to simply shut off the fuel supply at WOT.
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I agree with lazy JW.

So no EGT, what about an Ox sensor based AFR system? Instead of trial and error you would get a dirrect reading that should tell you a lot about whats going on. A Self Heated Ox sensor can be mounted perty much any where in the exhaust track thats above the water line.
 
69.5Mav":2cx4acn7 said:
Lazy JW":2cx4acn7 said:
Yup. The easiest way to check that is to simply shut off the fuel supply at WOT.
Click to expand...

I agree with lazy JW.

So no EGT, what about an Ox sensor based AFR system? Instead of trial and error you would get a dirrect reading that should tell you a lot about whats going on. A Self Heated Ox sensor can be mounted perty much any where in the exhaust track thats above the water line.
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There really is no place in the exhaust system to get any kind of sensor mounted into the raw exhaust flow. The manifold has water jackets incorpoated into it...kind of like an engine block.. The water is introduced into the exhaust system in the aluminum elbow at the back of the manifold.

As for shutting off fuel at WOT...what are you wanting to check for? I know in sleds, we would read plugs after a WOT run... problem here is I cant even get close to WOT .

.
 
Lazy JW":3a7if6xo said:
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
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I'm often not very good at explaining my crazy ideas.

Going WOT is easy, just open the throttle as far as it will go; getting the engine to respond is the issue. According to your latest efforts, the engine will now hit 3K; just get it there and shut off the fuel while holding it at WOT; if the trouble is due to an overly rich condition there is always extra fuel puddled up in the intake manifold/ports, when it runs out of fuel the engine will BRIEFLY pick up speed, then promptly die. You will need to be paying close attention to actually observe this, and if the problem is due to something (such as lean) then it won't respond in this manner. Since you already tried ADDING fuel via squirt bottle, that would seem to eliminate the lean scenario, and you have also pretty much ruled out ignition. IIRC correctly the compression is tolerable which doesn't leave much other than a rich condition in the carb.

I really dunno, and without actually being there to do hands-on troubleshooting it is indeed difficult, and since the "normal" things haven't panned out it may be time to try some weird stuff.
Joe
 
64 inboard

A sound file of the engine when the problem occurres might help to identify what is happening
 
Havent worked on it for 3 or 4 weeks.... I have a mechanic friend planning to go out with me some afternoon next week. I think I found an old Rochester downdraft carb I might be able to jury-rig temporarily, so I can eliminate the sidedraft setup.
I want to start with it the way it is to see what he thinks.

I really need to figure out what is wrong before winter.... :unsure:
 
you might look at the exhaust. A very restricted exhaust will rev at idle but won't flow enough under load.

it might also be timing. I don't know what the vacuum port on that carb might see, but if you hook a loadomatic to manifold vacuum, then time the engine at idle, you'll get an immediate loss of a lot of advance. The engine could be seeing several degrees at idle but put it under load and the advance goes away along with the power. It'll act like it ran into a wall.
 
My boat has cost me very little this season. Storage place called and said if I am not going to pick it up I have to pay another $30 and next winters storage fee is almost due also. Even if you dont use them they suck money.
 
MustangSix":2kf554p4 said:
you might look at the exhaust. A very restricted exhaust will rev at idle but won't flow enough under load.

it might also be timing. I don't know what the vacuum port on that carb might see, but if you hook a loadomatic to manifold vacuum, then time the engine at idle, you'll get an immediate loss of a lot of advance. The engine could be seeing several degrees at idle but put it under load and the advance goes away along with the power. It'll act like it ran into a wall.
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I have a friend that lost a bet on exhaust restriction... I changed the exhaust from rubber hose(which was a little loose inside) to steel this summer, so that is all new and open.

As for timing, I had someone advance and retard the dizzy while under way. This should take any advance issues completely out of the equation? BTW, the dizzy is all mechanical..no vacuum advance. Since then, I replaced the complet dizzy with another.

a couple other notes...The engine idles around 18" vacuum @ 10 BTDC...... fuel pressure is a little high @ 9psi.
 
When you get the problem solve you'd better post result and fix or I'll personally drive over with my battery power drill and a 2" hole saw to float test. ;)
 
Thad":2qzr9igs said:
When you get the problem solve you'd better post result and fix or I'll personally drive over with my battery power drill and a 2" hole saw to float test. ;)
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Bring a 3" hole saw! :LOL: and... I would be more than HAPPY to let you all know if/when we figure it out!
 
64 inboard":1j6pc49a said:
Thad":1j6pc49a said:
When you get the problem solve you'd better post result and fix or I'll personally drive over with my battery power drill and a 2" hole saw to float test. ;)
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Bring a 3" hole saw! :LOL: and... I would be more than HAPPY to let you all know when we figure it out!
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Much better :nod:
 
One more weird possibility. If the cam were installed with the cam advanced one tooth off, it would idle fine and make no power at higher revs. You might be able to check with by measuring lift against a degree wheel.
 
69.5Mav":1vyd5a8m said:
Any Progress?
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Wellllll, ..... We may have figured it out... I had some friends go out with me last Saturday... I installed a 1bbl downdraft carb off of a car and plumbed a fuel pressure gauge into the line. One of the friends ran the throttle while I drove. It ran great ... for about 25 or 30 seconds, then fell flat on its face, like it had been doing. The fuel pressure had dropped from 8lbs, down to zero right before stumbling.

A quick update on the fuel sysytem... tank had been opened-cleaned and fresh liner installed, freshly rebuilt mechanical pump on engine, new fuel filter/water seperator installed and all new fuel lines. I had been running a Carter electric fuel pump on the boat for the last 5 years. The guy that rebuilt the mechanical pump said it was ok to leave the electric one in the line, before the mechanical one, as a back up.

We decided to run a temporary hose around the electric pump to bypass it.... We were on a small interstate pond, so it was hard to give it a good test. We did make 4 or 5 passes and overall it ran pretty good. I then installed the sidedraft carb with my homemade adapter back on the motor. There is a bit of a high speed bog, that hopefully some carb tweeking will take care of.

When I got back to the shop, I removed the electric pump and it wont do anything when bench tested. The only thing we can figure out is the electric pump must have some kind of a restriction in it when the fuel flow rate is at a certain level?

I am hoping to get her out another time or two to check it out some more, but the season is getting real short up here.

Keeping my fingers crossed!
 
Good catch. I thought it sounded like fuel starvation but did not want to commit to any thing. Thats why I was hoping to see what your mixture was doing when this happened, I thougt you might be going lean. My wifes Sentra had a similar problem, turned out it had a plugged fuel filter and when she had to clime hills the car would run out of power.

I hope this solves it.

Good luck.
 
Fuel presssure. That is my first guess. 9 is a lot for a rochester. It really depends on the diameter of the seat. A high flow needle and seat combined with a brass float will not tolerate as much pressure as a small diameter needle and seat with a phenolic float.

Stopped up air bleeds can cause a poor mixture condition. A really wet mix would be noticed more on 3 and 4.

It's close to being overcarbed, a small problem with the carb will be seen as a huge problem on a small engine. Overcarbed seems to work on boats, but it can amplify the problem.

If that doesn't work, another carb would be the thing to try. Or the old carb.


The water in the exhaust. You may be able to shut off the water temporarily, but this will raise power, regardless of whether or not it's stopped up. So the results will be misleading.
Speaking of stopped up. Our friends known as dirt dobbers or mud dobbers have cost boaters billions of dollars over the years. Always defend your boat against these evil bugs. Screens and pantyhose are valuable defenses against them.
 
The carb that I'm running is a Carter YH sidedraft model. That is what the boat came with from the factory. I 'ponied-up' and bought an NOS marine one that I found, so the carb body is a brand new 1965 vintage, and should have no internal passage issues. It has been updated so the 8 to 9 lbs of pressure is ok.

I'm hoping to get the boat out this weekend to do some more carb and timing tweaking.
 
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