First Splash!

[inthedirtagain]

Picked up my 81 Sun Ray last fall and promptly stored after winterizing. Took it out today after spendy the last month cleaning up wiring, connections, and installing a stereo. When at home and on the hose, the 3.8L fired up pretty easy with the electric fuel pump and manual choke. Out on the lake today, it was a difficult process. Pretty sure I'm gonna need to learn this motor's starting ritual.

Once started, I had to carefully advance the throttle in just the right way or it would die each and every time. Would occasionally backfire, too. I managed a GPS-verified 31mph @ 3000rpm. That's it. Not gonna lie....I was disappointing and hoped that I didn't buy someone's problem child. Before anyone asks, I did verify the hull is clean (fresh water boat), all gear boxes were drained and filled with fresh gear lube, and the prop is a brand new stainless PowerTech 4-blade 15x15p.

I'm the cabin tomorrow with my other boat for a weekend of fishing with the family. When I return, here is my plan:
1. Verify compression, base timing, throttle advance, accelerator pump, condition of points/cap/rotor, and inspect spark plugs. Replace anything necessary.
2. If all that checks out, I'll place it on my old Sears engine analyzer to check /adjust dwell and use the tach function to adjust idle jets and final idle.
3. If that still doesn't get me running out better, I'll spring for either a new carb or a rebuild kit.

Trying to get this thing prep'd for a family reunion next month. Will be nice to finally wakeboard behind a boat with a tower! I'm using a factory OMC manual to get my specs for of this. Thoughts? Comments? Derogatory remarks?

 

[alldodge]

Don't know what kind of gas filter is on the motor, but remove it and pour contents into a clear container. See if the gas is clear and there isn't anything else in it

If its clear and good, then get a carb kit and rebuild. If its not clear, still may need a carb kit but would need to get rid of the bad gas

 

[cptbill]

I don't know much about Sun ray boats but seems to me 31mph with a 3.8 v6 isn't bad, though does sound like cap, rotor , wires and points just might do the trick for the rest of it

 

[inthedirtagain]

It's just your typical 19ft BR, nothing special. I know the operating range of the 3.8L is 42-4600rpm. I'm nowhere neat that. Will also need to verify that full throttle at the helm is also full throttle at the carb. Digging through my factory service manual and can't find if its safe to run the controls in/out of gear when the engine isn't running.

 

[inthedirtagain]

Fired up easily at home today with a couple of pumps on the stick first. PO installed a manual choke cable that wasn't working very well, so I removed it. Cleaned out the spark arrestor with injector cleaner. Holds a steady 13in of vacuum and I can't reach the adjustment screws to alter or improve that number.

Will install new points/condenser tomorrow and verify timing. I do verify that full throttle at the was also full throttle on the carb. More to follow...

 

[southkogs]

I might be reaching a little here, but look at your prop. '81 OMC would be a Stringer, right? 15" diameter seems large for a Stringer. Most of 'em were closer to 14" diameter. IIRC, my boat was a 14x16 on a straight six.

 

[inthedirtagain]

I took the specs from the prop and looked them up on their website, so I know the prop is accurately described. Looking in my OMC manual, a 15p prop was a standard option. The prop finder on this website lists 3 or 4 blade props (15p) in diameters ranging from 14.5 to 15.75 inches. I could try dropping down in diameter to see if the 3.8L can spin it faster, but its a $140 gamble.

 

[alldodge]

See if you can find a prop repair shop. Many let you buy one and exchange it a few times if needed

 

[inthedirtagain]

I live in BFE Montana in a town of only 600 people. There is literally NOTHING for marine repair out here. I'd have to go halfway across the state and even then, no one touches OMC. I've already called....

So back in the shop, I got out a few tools and did some digging around. All six plugs look good with no signs of fouling. Just tan in color with no deposits. Oil is leaking down from somewhere and there was a little oil on all the plug threads, but nothing major. Cleaned them up and reinstalled after a quick compression test. All cylinders hitting between 115 and 130 lbs. Took a look at the cap, rotor, and points. I'll need to order another cap and rotor, but these are usable for now after a quick polish of the electrodes. Points were shot, so I tossed on another set. Will get out my engine analyzer once it cools down a bit, verify dwell, and then check timing. Have a feeling it's off a tad.

 

[Redrig]

What's your elevation up there in MT ? I'm in slc at about 4500 and do most of my boating anywhere from 3500 to 8000.

The reason I bring up elevation is 13hg in vacuum is dang low . elevation impacts readings , but When I am messing with my engines in slc I am at about 18 -19 when they are in good tune. I'm not sure ive seen an engine running below 15 whether beaters , motorhomes, boats ,whatever at least on my gauge.

I wouldn't mess with prop yet , give that baby a full tune up and dial in the carb , I bet that fixes your vacuum and subsequent other issues . I am guessing you are just way out of tune. Check out the stickies for dialing in the carb and points

And kogs , you're not wrong . Electric stringers were 14" , the 800s though have 15" for stock props

 

[inthedirtagain]

Live at 6k elevation and play in local waters between 55-6500 almost exclusively.

 

[Redrig]

I bet your 15p is just fine. I use a 14 but only at the mountain lakes above 7k and fully loaded , otherwise my 16 works good (302 in a 18.5 runabout)