Need Help with 170 boat motor!

[Lazy JW]

....... we squirted gas in carb also when it was stumbling...made it worse........

Hmmmmmm......... I would have thought that would have pointed us in the right direction but apparently this is not an infallible technique.

 

[64 inboard]

....... we squirted gas in carb also when it was stumbling...made it worse........

Hmmmmmm......... I would have thought that would have pointed us in the right direction but apparently this is not an infallible technique.

besides that quirk, I had also used another electric fuel pump that I use around the shop,one end in a 5 gal gas can, the other hooked directly to the carb...it still had the stumble. made it kind of confusing... I am hoping to take it out this weekend for some more testing. I have been disappointed so many times, its kind of hard to get overly excited just yet.

 

[jamyers]

I haven't been on here in awhile, and just read through this thread - and I'm thinking that 8-9 psi is too high, or you need to lower the float even more. Do you know exactly how the carb was modded to handle higher pressure? Just about the only things that will overcome psi are a float arm with more leverage, a smaller needle-valve opening, or maybe a bigger float.

Higher fuel pressure calls for a lower float setting to yield the same fuel level in the bowl. For example, my HW5200 calls for 3-4psi and (iirc) a 40mm float height, but with the Ford fuel pumps' 7psi, I had to lower the float setting dramatically in order not to flood the engine on corners.

I'd recommend a good pressure regulator and gauge (stealthily mounted, of course), then at least you could monitor.

 

[echo1955]

Have you tried running through the RPM range with a vacuum gauge? It will eliminate a partially clogged exhaust system and reveal other possible issues.

 

[64 inboard]

UPDATE!!!!!

Been a while since Ive posted on the site.. thought I would bring you "up to speed". Between our schedule and the weather, we havent gotten out with the boat too much this summer... only 4 or 5 times. However, she is FINALLY running, and the best it ever has since I bought it!

I currently have it propped with a 12x12 wheel (12"dia x 12 pitch) ... with two in the boat, it easily runs up to WOT at 4200rpm's! That might not mean much to most of you , but that is the prop that a lot of v8's run! I still have some small tweaking to do, but for the first time feel like it is trustworthy enought to get us back to the dock.

I want to thank all of you for the input, and in particular, David S. for his handbook and all the phone conversations with suggestions. There is absolutely no way this would have come together without all this help!

If any of you ever get to NW IL and want to go out in the "hotwater 6" let me know!

 

[69.5Mav]

Hoody. Good deal, I'm glad you got it running to your satisfaction. What change would attribute the improvement to?

 

[64 inboard]

Hoody. Good deal, I'm glad you got it running to your satisfaction. What change would attribute the improvement to?

it was the dang electric fuel pump..... here is a copy of my post from last Oct.

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!

we ran out of time last fall to finish her up..been out 5 or 6 times this summer and so far,so good!

 

[bubba22349]

Glad to hear you are getting to go and use it some

 

[chad]

so far,so good!

No, I know U can't afford the luxury of this but I can (after followin dis thread so long):.
SUCCESS!!!

My automitive 170 has run sh^##ly 4 25 yrs n fixed it same way.