1977 305K losing power

Hello,

I have 1977 Chris Craft Super Sport with a 305K Marine Power engine. For the most part the boat runs pretty good, but after about 15 minutes of running the boat at various speeds the motor wants to bog down around 1200 - 1500 rpm. It will mostly run pretty good after a little hesitation, but generally the longer I run it the worse it runs. It also gets harder to start...starter drags....the longer I run it.

I've only owned it for a couple months, so I'm still sorting it out:
Mechanic fuel pump...looks like it was replaced at some point
Holley 4bbl carb
HEI conversion kit ignition, manufactuer unknown. It looks like the distributor is not a marine distributor, which is one of my concerns. It has connection for vacuum advance, but it is just left unattached? I'll send a pic. I've order what looks to be the correct replacement cap, rotor, coil, but if the distributor isn't correct for the motor, not sure I want to put replacement parts in it.
The boat also seems to run a little cold... maybe 125 F. Thermostat is probably stuck open.
Choke on carb is working good... stays open once it's warmed up.

Any help would be appreciated.

Engine running too cold. The P/O may have removed the T'stat to solve an overheating problem. CC T'stats not cheap or easy to find. SWAP the auto ( it has a vac advance) disti for a marine one. Not only is an auto disti illegal in a boat, it is dangerous, and besides, it has a totally incorrect advance curve... Fix the incorrect/missing parts first, they retest engine. FYI disti caps are also special marine.

Thanks for the reply sandkicker! Any recommendation for an aftermarket dist? The current one has an in cap coil, so I'd like to stick with that style. It's CW rotation.

The folks @ Delco have an aftermarket marine disti kit for SBCs, which I'm pretty sure what the 305 in your boat is based on ( Disti aft or fwd on block??) Their standard catalog model apparently is not listed for an engine your age, but a phone call is worth it. Re: Coil in cap... forget it.. you won't have a choice)

Davis unified ignition products are another option...and true voyager conversion kits are hard to find.

Anybody have an opinion on a Pertronix (D200810)? Trying to find something that reasonably priced that's in stock somewhere?

Thank you very much for the replies!

I found the Voyager kit at Michigan Motorz. Should have it installed in the next few days.

Also replaced the old crusty t'stat with a new 140 deg t'stat. T'stat and the rest of the raw water cooling system seem to be working ok.

More engine test info to come after I get the disti installed.

IF t'stat was working, soak it overnight (or longer depending on crustiness) in white vinegar... keep as spare.

Got the disti installed over the weekend. Setting the base timing gave me a little trouble. Attempted to follow the instructions provided with the disti. Using the timing shunt to bypass any advance set base timing at 10 deg BTDC. Two problems I encountered:
1. Starter drag on restart
2. High idle, even after turning out idle screw

Ended up taking out some of the advance and got to about 9 - 10 deg at 800 RPM without the timing shunt. Pretty sure the advance is already starting to show up at 800 RPM. Also, would fire right up on warm restart.

Test run seemed promising at first; smooth running under load at idle, nice throttle response getting up on plane, smooth running at various RPM, but WOT a little low @ 4000 RPM. Only ran WOT for a few seconds. Of course, after about a 20 - 30 min test run my problem resurfaced as I was coming off plane. Motor RPM's surging and it even stalled, which I never seen before. Was able to restart and idle, roughly, back to the dock.

In addition to fully understanding my base timing, I think my problem may be related to fuel delivery? I changed the fuel/water separator a couple months ago, but there is no other in line fuel filter. I have fuel system experience with my similar year GM big blocks, but I am curious what should be sequence of filtration from the tank to the carb. Specifically, in this case if I add a simple in line filter should it be before the fuel pump? Also, I don't know yet if there is a carb inlet filter on this Holley similar to the Q-jets on my big blocks. The housing where the fuel line enters the carb seems a little small for a filter. Some of the fuel smees a little stiff, so while I'm at it going to just replace all of it from the tank to the carb.

Thanks again for ths replies!

If you installed the EST kit, I'd suggest just setting the timing at max advance and live with the idle.... the advance curve starts real early IMO....

A water separating spin on filter is usually adequate and its typically installed on the suction side of the fuel pump...

may want to replace the anti-syphon valve is you are changing the hoses....and make sure you get the 'approved' hose...

Re: "I changed the fuel/water separator a couple months ago,"

In this world of ethanol "enhanced" gas, a spin on water separator/filter can get "full" of water to the point where the engine runs crappy. It then needs to be emptied or replaced. ( after running as little as 10 gallons of fuel through the engine!!) .... While the "Filter" portion of the cartridge will hold a fair amount of crap and still flow, the water separator portion only holds a few ounces of water...after that .... crappy fuel into carb.

Thanks a lot guys!

Still chippin' away at this one...
Found the anti-syphon valve removed by P/O, so had install a new one. Still working on fuel hose replacement, but found carb inlet filter pretty fouled. White kind of powder/slurry with some finding it's way past the filter into carb inlet housing. Found the moraine brass filter at the local auto parts store, as well as the complete Holley replacement filter kit at Summit. Just concerned that some contamination may have pushed it's way past the filter into the carb. Also, going to install a fuel pressure gage just prior to the carb to help with troubleshooting.

Still fortunate to have non-ethanol gas at the marinas here in West Michigan, but I can only account for fuel history over the last couple months. Makes sense to refresh the separator again. At some point may have to dig deeper into the contents/condition of the fuel tank.

re: "but I can only account for fuel history over the last couple months. Makes sense to refresh the separator again. At some point may have to dig deeper into the contents/condition of the fuel tank."

EASY.... get a wide mouth glass jar ( peanut butter) that is about the same diameter as the filter. Carefully unscrew filter taking care not to spill any gas... Carefully pour the total contents of the filter into the jar.... cap it and wait 20 mins... Water, if present will separate into a layer at the bottom of the jar.... dirt will also settle to bottom. Take note of the color of the top (gas) layer... if dark, fuel is compromised.

Perfect! I haven't changed out the filter yet, so I'll use this technique and report results.

Thank you very much!

Well Sandkicker, you nailed it. The contents of the fuel water separator looked awful. Reddish- brown with distinct phase separation. I was a little surprised, because when I changed the filter right after I bought the boat the contents of the filter looked "clean." Anyway it's trash.

I'm now wondering if the gas tank shouldn't just be replaced altogether? I can siphon out rest of the gas and remove the tank? Maybe try to clean the tank or replace it?

Side note - seems like it should be easy, but haven't been able to figure out how to post pictures on the forum?

Thanks,

Mark

The tanks can usually be cleaned...if you have easy access to the tank, you may want to try to remove it.

Many times, its easier/quicker to take it to a service provider and have them clean it and dispose of the old gasoline ... check w/ you local marina for recommendations...or use your favorite search engine...

Get a quote from a service provider per makomark. Some charge outrageous amounts depending, I suspect on the difficulty in disposing of the current fuel in the tank in your particular jurisdiction. If fuel is reddish brown as you say, its beyond rehab ( use an enzyme fuel conditioner and add back an octane booster for mild degradation) .... Much depends on how much gas is involved in the tank... ChrisCrafts of that era usually have quite good access to the gas tank. If possible inspect for rust, inside and out. New aluminum tanks can be... pricey.