Starboard Engine burning more fuel and can't get over 2800 RPM

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1965ShepherdCruiser
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Starboard Engine burning more fuel and can't get over 2800 RPM

Post by 1965ShepherdCruiser »

I hope this isn't a problem but I have a 1965 Shepherd Cruiser (Trojan bought Shepherd in the early 70's I think).
She has twin Crusader CH220's (Chevy small block 305's) from 1983 approx.
My fuel burn on the starboard engine is around double the port. I also can't get starboard engine over 2800 RPM.
I've been trying to diagnose it but I'm feeling a bit stuck. Leaving for desolation sound on the 24th of Aug and was hoping to have this more dialed in by then.
-Distributors are pertronix flame throwers. Springs seem good on them. Cleaned up contacts inside cap.
-Both idle vacuum at 18. At 2000 RPM under load port vacuum is 16 and starboard is 10.
- sprayed brake cleaner around intake manifold and bottom of carb but didn't cause any kind of revving. I was pretty sure I had a vacuum leak but it seems not.
- I advanced timing on starboard by 2 degrees and it inproved idle vacuum sigificantly but seems to have made no difference in vacuum under load. Going to change it back to originak timing mark
- next steps were going to be swapping carbs and ignition coils to see if problem followed either.
- props are a bit of a wild card. Port side is stamped 16x14, 16x15 and 16x16. Starboard is 16x14. The port side is a lighter bronze prop by unknown mfg and strbrd is heavier broze prop by Osborne. I had an extra set repoitched to 16x14 and tried to install them while on scuba but I'm going to need to heat up the props to get them off, prop puller did nothing. Hard to tell obviously but the props look like they are pitched the same when you line up by sight.
- those vacuum gauge guides say a steady vacuum reading of 10 is indicative of late valve timing. I don't really want to get into advancing the cam until I've crossed out all other possibilities.

Anything else you all suggest I try? I'm all ears.
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prowlersfish
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Re: Starboard Engine burning more fuel and can't get over 2800 RPM

Post by prowlersfish »

Do you know your trans gear ratios? Are both the same? Most likely your starboard engine is reverse turning (RH) Does it have the correct marks ? Timing set accordingly? If all that is in order The props would be the next thing to look at.
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1965ShepherdCruiser
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Re: Starboard Engine burning more fuel and can't get over 2800 RPM

Post by 1965ShepherdCruiser »

Both are 1.52:1 Bennet Velvet drive. Strbrd is reverse turning so I do expect a little more fuel burn but not twice as much.

Yea, I may try getting her on tidal grid this Sun to swap out props.

Timing marks on harmonic balancer only show TDC mark but no degrees on either side. Somebody marked it with whiteout, the stationary marker has a white mark on it thats not on the edge you would use to line up TDC though. Where the extra mark is retards the timing though and idle vacuum gets pretty low if I set it there.

The thing that has me questioning whether or not its props is the port engine (good engine) is marked 16x14, 15 and 16 ( they are all marked over each other). The strbrd is only marked 16x14 so it seems like the over pitched side would be on the engine I'm not having issues with getting up to speed?

That being said, I'm brand new to all of this and literally grasped an understanding o engines about 2 weeks ago so I'm no expert on any of this.
mikeandanne
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Re: Starboard Engine burning more fuel and can't get over 2800 RPM

Post by mikeandanne »

One more thing, check to make sure the distributor is advancing the timing from idle properly. Have you had this boat for a while, is this just a new occurrence ?

Also check your PCV valve is working correctly.
mrrudely
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Re: Starboard Engine burning more fuel and can't get over 2800 RPM

Post by mrrudely »

choke?
10 meter mid cabin
1965ShepherdCruiser
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Re: Starboard Engine burning more fuel and can't get over 2800 RPM

Post by 1965ShepherdCruiser »

So a quick update.

I checked advance on the distributor and put new springs on the mechanical advance. I don't have a degree marker on my harmonic balancer. The indicator mounted on the block shows 8 degrees in one direction and 12 in the other from 0. Just a mark where TDC is on the wheel. It should sit at 10 degrees at idle and advance to 34 degrees with my Pertronix Flamethrower. It seems to be working properly.

Before going out for a test run I checked #1 plug and it had quite a bit of carbon on it. Not really any build up but quite black.

I swapped carbs just to see if a stuck float was the issue.

Swapping carbs did nothing. Same engine having issues. When I get to 2600 RPM it really starts struggling to get past. I was able to get it up to 3100 RPM but the rpms would drop off to 2600 then go back up and then back down.

So now I'm thinking maybe it's fuel supply shortage (which doesn't really add up because this engine is burning almost twice the fuel of the other one.). Out of curiosity I opened the valve that connects my two tanks and it seemed to alleviate the fluctuating rpm's a bit. I would swing by 200 rpm instead of 500. Both fuel filter/water separators are brand new and just installed new filters in the carbs.

So I'm at a bit of a loss. My next steps were going to be a new distributor cap, new plugs and new wires. My gut tells me fuel supply isn't really the problem bcause that engine is burning SO much more fuel. If anything maybe it's getting too much fuel. But whatever the problem, it isn't being driven by the carb.

I had a compression test done in Oct so I wasn't going to do it again but maybe I should just to rule that out again
.

To answer a previous question. We bought the boat last fall, that engine had overheating issues that a mechanic had worked on but we never really found this because we were happy cruising at 2000 rpm at 8.5 knots and when we did the mechanical survey that engine did the best on the compression test and the other engine threw a low oil level alarm so we spents a bunch of time sorting that out. After that we ran it one time with no problems up to 3400 rpm at 18 knots and then I hadn't tried again until recently. We spoke to a few owners (of very similarly sized vessels) at a wooden boat show who said they all cruise around on plane at 18-22 knots using 2 liters per nautical mile and I got intrigued to see if we could speed up our travel and halve our fuel consumption.

When I swapped carbs I reset the vacuum idle adjustment on both. They were both turned different amounts but also way too much. I turned each 2.5 turns from closed and will vacuum test to fine tune.

Choke is on a heat spring and seems to work the same on both engines. Opens right up as soon as the engine gets going.

Last thing I suppose is that it could be prop related. I have a nice set of confirmed 16x14 props I'd like to put on to rule that out but taking them off in the water didn't work and our tdal grid is booked up for weeks.

I would just use a boat lift for the day but it blows up our chines so I avoid that unless it's absolutely necessary.
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