Hard to start problem.
 

I have a 1999 382 Fastech with 502 mags. Seems lately each time we go out the engines at one time or another don't want to start.

I'm beginning to think its heat related ?? It's been in the mid 90's and sunny here. This past weekend we had ran out in the gulf for a bit and then to an island to swim and listen to the radio. I'm always paranoid of the batteries going dead so I start the engines after about a 1/2 hour of sitting. What happens is the engines crank as normal, seem to start to fire and then die. I try again and again. Usually it seem when crack the throttles and randomly it lights and once it revs and starts is good. The second engine still wouldn't start so I let it set with the first engine running for about 5 minutes and the finally right side started.

What would be common to both engines ?? The right side seems to do it more the left. Never does it on the hose. Only seems to be doing when heat soaked. Thanks for any insight guys. SJ

If their mag MPI, cool fuel engines, its defiantly heat related, when you say right engine what one are you referring to, do you open the hatch a bit when stopped,

Yes, I would concur that it is heat related.

502 MAG MPI's are susceptible to heat soak / vapor lock - the first gen with the VST, in particular. Especially of your a using ethanol fuel from the local gas pump.

Mercruiser put out a technical service bulletin on the issue.

heat soak.....lift the hatch for a few minutes when you first shut it down to let alot of heat out. open it again 5 min before starting if possible and I bet it never happens again.

Vapor lock.

Many of us have/had same problem on 502 MPI's. I went the Merc route and installed their add-on pump. It worked really well, and I never had the issue again (you can install this yourself easily). Others have run return lines back to tank, installed better pumps, etc. Many ways to skin a cat.

I usually do not open sun deck. I guess in boat talk I mean Starboard side. Lol. Thanks.

Yes, I normally run just station pump fuel that usually has the up to 10% ethanol in it. I normally just put low grade in it as well. Would higher octane be less likely to give trouble ??

What is VST ?? Not sure what your talking about there. SJ

What are the add on pumps you mention ??

Is the main issue just a heat vapor lock type issue or do the fuel pumps get week over time ?? I'm the type if the two fuel pumps were just showing their age I would replace if I knew it would solve the issues.

Thanks to you all for your input. It's very much appreciated. SJ

I can't understand why people put in low octane fuel..... How about we look at this in a different perspective.......let's say you want to bang this hot girl but you have to get her drunk.... What do you buy her? Wine coolers or Jaegermeister shots. Wich one will get you there faster before she starts crying and you realize she is too drunk? And say stuff like I don't normally do stuff like this? My question is .., if she doesn't normally do stuff like this then why the hell is she so good at it? But what I'm trying to say is the more efficient the fuel energy the more the " bang" for your buck. So buy paying less at the pump your getting less energy per gallon therefore less fun for buck. Your ony seeing the cheaper fillup but not how fast it's gone....or.... If you did 100 shots of beer or 100 shots of Bacardi 151 ...get it

be careful what you ask for, if you have the cool fuel system the fuel pump is clear down under the port motor mount next to the oil pan, I changed mine in my 33 OL but its a PITA.............. VST system has the fuel pump mounted on the sea pump housing, I think

Drew's Skankizam means put some ethal in it man, LMAO............:lolhit:

In New York it all has ethanol in it. Not that anyone wants it. And we still pay road tax at the port fuel pumps...... All I'm saying is if you have knock sensors and wand to run slower or detonate your motors run **** fuel.......:chill-pill::

battling the same issue, however its only on the port motor, we have had ethonel for a few years, so something has changed, everytime I ask someone i get nothing except changing my entire fuel system, there has got to be a reason why now this is happening had the boat 4 years and run it in plenty hotter/humid weather, w/o issue, Ive been running my blowers all the time never done this before, don't think it helps much thou, maybe a little

My thought is after having to readjust my floats on my carbs this year from last year is the fuel co. Statement of " at least 10% ethanol " really means 30% or more. The fuel is less dense therefore the floats sit lower. The ethanol co. Know that the end of the line in coming. Considering it takes 3/4 of a gallon of fossil fuel to. Make one gallon of crap the screws up all motors and fuel lines.

Drew I don't know how old you are but back in the day Ethal ( red neck talk ) meant premium, Phillips 66 red in color and about 98 octane, that's all

I get it I did misread your post. I ment no disrespect......lol.

Thanks guys for your input. I'll let you know what I figure out. SJ

No it's an additional pump that helps to push the vapor "bubble" through the upper fuel system and through the injectors.

One was just posted for sale. I think I paid about $400 for my kit - this one is cheaper.

http://www.offshoreonly.com/forums/s...3-new-box.html

IAC ...... 805224A1 ........

http://www.mercruiserparts.com/Show_...+INTAKE+PLENUM

#34

did u ever get anywhere on this? had it home last week and I found the return line from the bottom of manifold plugged solid, I think the line has deteriorated due to ethanol, I unclogged it, ran all new lines, put a can of k100, and filled up on non E and did not have a issue last weekend, I will know more after this weekend it is sposed to be hot, but so far I thinking maybe that clogged line, but what throws me off is the fact that both motors were plugged, only having a issue with the port, we shall see,

I still have one engine out and it will be going back in Monday. I'm putting two new fuel pumps on and the new cool kits too. Not to mention all new exhaust manifolds, risers, and elbows. Lol. Should be back out next weekend.

Try to stay away from regular pump gas with ethanol. In Florida, non-ethanol fuel is called REC-90 and many road stations are selling it. Try to use that instead. Ethanol is an alcohol which has a lower boiling point.... when the engine compartment gets warm, the alcohol boils, creating pockets in the fuel lines and fuel rail.

I think this has been kicked enough, but VST is the Vapor Separation Tank, it is mounted on top of the engine and at the rear port side. Fuel gets pumped into that little tank via a mechanical pump mounted on the raw water pump (or maybe a regular mechanical fuel pump, depending on engine vintage - not 100% certain on that), and then a high-pressure pump in the VST tank pressurizes the fuel rail.

Great info as well. Thanks guys.