View Full Version : Engine dies sometimes when warm...

07-11-2010, 10:46 PM
Just got back from the lake second time out. The boat seems to run great until my wife took he helm and we went to trailer it. Then it would start and die if on idle. Pulled Neutral and gave it some gas, started but would die when the trottled back to idle. I hopped in and was able to get it running and then on the trailer by feathering the trottle, it died a couple of times on me. We had similar problems last year.

Good power during the day, topping out at about 4000 RPM's. We have new gas in the tank, non ethonal 89 octane.

The boat is a 88 Tristar, with a 351, holley carb, still running points and condenser, 496 hours on the engine.

I have replaced the following over the last couple of years:

Plug Wires
Cap Rotor
Pulled the tank sending unit and cleaned the whole tank and pick up
New fuel filters

The only thing new this year is the oil and oil filter. Also the Impeller and Thermostat (140 degree).

I've got a new electronic ignition and coil on order, from Hot spark.


07-11-2010, 11:56 PM
Points are always a likely source. What RPM is it running at in neutral at idle?

07-12-2010, 12:42 AM
I think it's running at about 800 to 850. Which is set a little higher than spec but we are at 3000 ft and it is an older boat...

07-12-2010, 01:27 AM
I would run through all the basics. Look at a couple plugs. Pop the dist. cap off and make sure the contacts aren't all corroded. Visually inspect the points. Check all plug wires for a secure connection at each plug. Make sure that the plug wire connection at the dist. cap isn't all corroded. Same at the coil. Check your point dwell and timing. Check for vacuum leaks at the carb base.

Most likely one or a combination of these are the source.

07-12-2010, 09:39 AM
I went to check the battery and the Negative cable connection was barely on. 1/4 turn of the wrench and I was able to pull it off the battery. The volts were running below 12 at idle, thoughts on this being the culprit?

I've got the battery on the charger and should get the Electronic ignition and coil today. Hopefully I can change them and get it timed. Leaving on a boat camp trip on Weds early AM...

07-12-2010, 09:44 AM
If your points or something else in your ignition is marginal, low voltage could cause that. At higher RPM you would be seeing greater alternator output which could overcome the bad connection. But then again...................?

07-12-2010, 09:51 AM

07-12-2010, 11:12 AM
Once the motors reved the voltage goes up on the guage and it runs fine.

Put the Battery on the charger last night 12 hours so far at 2 volts Deep cycle. The battery was new last year and just charged two weeks if that ago. So I'm thinking theres been a drain on the Battery, we were kicking on the water with the tunes going. But running it around and to the boat launch should have charged the Battery, if everything was connected.

07-12-2010, 11:15 AM
P.S. I got water pump gaskets at an auto parts store and they matched up with a 1969 351. This is old, 40 year old technology.

07-13-2010, 11:21 AM
Changed out points and condenser to Electronic ignition, put a new coil All from Hot Spark. Hot Spark has good prices but NO CUSTOMER SERVICE. The install was pretty easy and the motor runs/idles but the timing might by off.

Will be changing out the Cap and Rotor, reseting timing and idle.

Heading for a long Boat Camping trip. Hopefully all will be good.

07-13-2010, 11:23 AM
Sounds like you are making some progress.

07-22-2010, 12:00 PM
Had the timing set at 10 degress BTDC in the driveway at 800 rpms. After changing the cap and rotor, it was looking beautiful at idle and then would advance seeming nicely at higher RPM's, no spec on that and my light doesn't have an advance. Then got on the water hours from home, was so confident that I didn't take my timing light, not a smooth move.

The engine idle great and ran great at no wake speed, but it would not go on anywhere when I hit the throtle. Just bogged, spuddered and died. So I popped the cover and messed with the timing to get some speed, opened her up and tweaked the timing until I got max RPM, figuring that might be a good timing point. That was great at speed but she wouldn't idle. Some adjustments to the air idle mixture and we were able to ski but she ran like an old outboard, no power, etc....

Maybe some fuel/carb issue. Anybody have a standard on Max RPM's, ie top speed? I could have sworn she used to hit 4300 but now seem to be topping at 4100 RPM's.

07-24-2010, 11:25 AM
Went back to basics and pulled spark plugs. I hadn't messed with them after last seasons winterization. 7 of 8 looked great (Like New), couple of the gaps were slightly off. #5 Hole's plug was fried. Quick research looks like advanced timing issue. I was all over the place with the timing trying to time it by ear. One dead hole definite problem, when is the question. I'll run a compression check on that hole.

Also pulled the Water seperate filter, could use a change.

07-24-2010, 11:59 AM
Sounds like you know what your doing. Keep up the post, some of us are learning a thing or two from it! Thanks!

07-30-2010, 02:59 PM
Replaced that fried spark plug, it's a mystery when it when bad, replaced the fuel filter in the canister, got both at Napa.

Three things every spring will be Oil/Filter, Check Spark Plugs and lube/check impeller. Yeah you can replace the last two but with less than 50 hours per year, I think that would be overkill.

When out on the Lake, boat was running great and got progressively worse. Could pull a skier/wakeboard so we floated and enjoyed the day. Got back on the trailer no real power but was able to make it on a plane. Everything now seems to point to the Carb. Ordered a Carb Kit from Jeggs, great deal, they even shot me a hat. Pulled the carb out of the boat and notice that the secondary plunger rod wasn't clipped in or attached to the secondary linkage, there's kind of a lame little C-clip. Could have been the problem, as that would explain no power and other problems if the secondary is floating free on it's own. Had the carb kit in hand so started pulling things apart. Gaskets, look worn and the Needles on the float were looking ready. The rebuild/tear down was a little intimidating but I'm thinking it was accomplished, very few adjustments really, just the Floats... Put it together and back on the engine. Engine started after getting fuel back in the bowls. Was running rich, oily looking plugs and exhaust.

Called Jeggs and Holley, got some tips on setting the floats and Fuel Idle mixture. I'm feeling confident that the fine tuning there will get the boat back to where it should be. Heading camping for the weekend, hopefully things will be dialed in by the end of the two days.

08-03-2010, 01:49 PM
Final thread on this one. Ran it over the weekend and seemed to progressively get better after the Rebuild and some fine tuning of the Air Idle screws. I pulled the plugs and they were looking great, now tan or clean as opposed to black and oily.

Excited to get back out and stop busting my knuckles for while on the engine.

08-03-2010, 03:42 PM
Sound like you won the battle.