Still Hard To Start??? Any ideas?

[rollenrock33]

I posted last week about back preasure being the culprit because the boat starts fine when its on the trailer with a garden hose hooked to it, but at the lake its a different story. The boat is an 87 Sunsport. It fires right up when I first get to the lake. Boat runs great, idle, WOT, cruise, whatever. Turn the boat off, sit for 30 seconds or less, fires right up. Sit for more than that, I have to put in neutral and the throttle to wide open and crank for about 10 seconds. Then it fires, runs fine.

The carb is a edelbrock 600 cfm marine, I know its not the stock carb. I rebuilt the carb, new needles and seats, set the floats to spec.

My question is, Could this be something other than the carb? I have been reading the archives and seems that a lot of old supra's had the same problem and fixed it by changing out the starter. I dont think it cranks much different on the lake versus the trailer but I could be wrong.

Does the fact that it starts with the throttle at wide open rule out the starter? I just don't think its the carb since the rebuild and the fact that it runs perfect other than the starting issue.

I think the difference from the trailer to the lake is the temp diff. under the engine cover. If not temp, its the angle that the carb sits from the boat sitting in the water.

Temp. difference makes me ponder the whole starter idea. The angle of the carb just does not make sense to me. I know Salty had said about getting a carb wedge but I just can't believe that supra would make a boat that would be so hard to start from the factory. Maybe I need to seet the floats deeper? Any ideas? Thanks again for all the help.

[michael hunter]

Supra didn't, when you changed the carb you changed everything. It sounds like a hot soak problem when you turn off the engine the coolant stops flowing. The engine temp will go up and can cause the fuel in the carb bowl to expand and flood the engine. You could try lowering the float level . Also Salys recommendation on the wedge is a good one. That carb was never designed to be set at an angle.

[rollenrock33]

Thanks Mike,

That makes sense as far as it starting great on the trailer with the hose hooked to it. It would stay much cooler with the water pressure pushing through the block even when it was shut off.

So pretty much has to be carb related? I know the edelbrock is not stock but it seems like a lot of other people on here with the stock motor and carb are having the same problem? Thanks again.

[rollenrock33]

I talked to edelbrock. They said that carb should perform great even at that angle. Told me to try a insulator gasket if that dosnt do it try a carb wedge. I will let you know if it works.

[Salty87]

i had suggested battery cables/connections in your previous thread. the reason i say that is because a hot engine is harder to start. corroded cables aren't efficient and rob your starter of current...electrical guys, correct my terminology.

this is a common problem in older boats too. like steering cables, battery cables don't last forever. if you can see corrosion on the outside, it's worse on the inside. bend them, do they make a cracking sound? connections clean? are you using wing nuts or terminals?...inefficiencies add up to a starter that turns over but just eventually drains the battery.

it's also quicker and cheaper to check. warm the engine on the hose, get some short battery cables from the auto parts store and move the battery close to the starter.

[rollenrock33]

Salty,

Thanks for the info. I will check that as well and post what I come up with. Gota love this site!

[rludtke]

I suspect that you may be encountering fuel vapor lock. This is the condition were the fuel vaporizes in the float chamber from the temperatures under the cowl.

Vapor lock is cause by excessive temps under the cowl, either air temp, or conductive temps transfered from the engine itself. This might suggest that your exhaust manifolds are not recieving enough cooling water from the raw water pump. The carb can not meter vaporized fuel, so the resulting mixture will not support ignition. The fix is to open the throttle wide while cranking to replace the fuel vapor with fresh (cool) liquid fuel. Then the engine can start.

I chased this problem for a while myself. The insulator plate you mentioned is a good idea, I have one (I also added a wedge, but I don't think it helped any). It will help insulate the carb from heat conducting through the metal. But this may not be enough if the air temp under the cowl gets too high. How long has it been since your raw water pump impellor was replaced? Replacing the impellor should help reduce the exaust manifold temps. Cooler exhaust should, I reason, generate cooler air temps. I just did this to my boat, as I was experiencing vapor lock issues at the end of last season. So far it seems to be improved, but I haven't put it on the lake yet to be absolutly sure.

[rollenrock33]

Hey guys,

Just wanted to let you know I think the carb insulator did the trick. I have also been running my blowers more to help with the air temps under the hood. So far I have had no problems with starting. I believe I am still getting some vapor lock though at high rpms. If I open the boat up above 3300 rpm I get a poping noise coming from the carb. Boat looses power and I have to back it off to half throttle or better for a couple seconds then it clears back up. Any ideas? Thanks again for all the help and for anyone having problems with the heat soak and carb flooding I would highly recommend a carb insulator and running the blowers as much as possible. The carb insulator was only 15 bucks or so from summit racing.

[87SunSportMikeyD]

Rollen - Have you checked your water pump impellor? rludtke may be onto something there.

[Salty87]

that's great to hear that you found it.

when was your last tune-up?...dist cap, rotor, condensor, points, etc.

[rludtke]

that's great to hear that you found it.

when was your last tune-up?...dist cap, rotor, condensor, points, etc.

I like where Salty is going, the popping is probably not a vapor lock issue, as the carb is in High-Flow mode (passing lots of cold gas) at that point. Usually vapor lock happens after shut down, and is noticed when you attemp to restart in the hot environment.

The popping might be ignition, and it could be mixture. if your ignition has been recently tuned, then you might have other carburator issues causing the mixture to go lean, such as a bad power valve (or comperable for the Edelbrock). Lean mixture will result in after-fire, which makes a popping sound. If it's been several years since the tune up, than you could have a weakness in your ignition that can't stand up to the stress of the higher power settings.

I used to have high air temps near the front of the right hand exhaust manifold of my motor home, and would burn up the ignition wire in that area when climbing the mountain passes in the summer. Loss of power and popping noises where the result. In that case, I increased the ventilation to the bad area of the engine, and now it doesn't ocurr any more. Check your spark plug wires closely, if they got too hot (generally), or if they have been burned by contact with an overheated exhaust system, they probably will not perform under stress any longer.

I am suspicious that your root cause is high temps from a bad raw water pump impellor, resulting in vapor lock condiitons, and damaged ignition wires from excessive exhaust temperatures. If your impellor is more than a year or two old, or if it has ever been run without water passing through it, I think you should consider replacing it. It is cheap and easy to do.

Let us know what happens...

Cheers,

[rollenrock33]

I replaced the impellor at the start of the season, so it should be good. My temp gauge never goes above 120-130 so I think thats all good. I agree with you guys and the more I think about it, the problem is more than likely in the ignition end and not the carb. I think summit has a electronic conversion kit for my dist. for about 80 bucks so I am going to give that a try and replace the plug wires. I replaced all the plugs at the start of the season so they should be good. I'll let ya know what I come up with. Thanks again for all the help.

[chautauquasun]

I had similar issues with mine last year. Mine would start fine when it was cool but when it got hot it was almost impossible to start. Like you it seemed like the starter would crank it over fine when cold or hot but I did some research online and found that when the 351 gets hot the compression goes up and put more strain on the old starter I had, it would overheat and draw too much current from the battery and it would then die. I replaced my starter with a hi-torque starter form DB electrical for $58.00. My starting problems went away completely. now it doesnt matter is it is hot or cold it will start the first time I turn the key. It was like night and day.

let me know if you want the link to their site.

Good Luck

Dan