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5.0/5.7 hard to start when hot

 
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times2



Joined: 24 May 2008
Posts: 2
Location: Kentucky

PostPosted: Sat May 24, 2008 9:12 am    Post subject: 5.0/5.7 hard to start when hot Reply with quote

OK I bought this boat last year. 1992 Bryant bbi200 originally came with a Mercruiser 5.0 (thunderbolt ignition). The previous owner claimed that the engine was swapped up to a Mercruiser 5.7 but had no paperwork to support this claim. I did find where "5.7" is cast into the block on the side of the engine. I don't think it makes a difference if it is a 5.0 or 5.7, and it does not matter to me as long as it runs.

Here is what's happening:
Yesterday I wanted to put the boat in the water for this first time this year... I have had the boat running on the muffs but wanted to put it through it's paces on the water.

-I pulled it out of the storage slip and drained the BRAND NEW Mercruiser water seperating fuel filter to make sure there was no trash in there at all (recommended by the mechanic who winterized the boat, he said the previous filter was just plain nasty).

-I filled the filter with new good gas and cranked it on the muffs to make sure I wasn't going to have a priming/no fuel problem when I got to the ramp. The boat cranked very easliy, I pumped the gas twice and returned the throttle lever to straight up and down in Neutral position and the thing purred. killed it and cranked it two more times back to back and it required no pumping or anything, fired up great

-I drove about 3 miles to the ramp, backed the boat into the water, and cranked it very easily - the first touch of the key fired it up.

-We ran the boat all over the lake for about 45 minutes. We stopped twice for less than 5 minutes each time and thought about getting in but the water was just a little too cold. The boat fired back up very easily both times, it fired like I want it to.

-After stopping the 3rd time I wanted to let the boat sit for a while to see if it would crank back easily (had this problem last year also). After sitting and talking for over 10 minutes I wanted to see if the old girl would crank up... and it would not. The engine spun freely but felt like there was nothing happening. Kinda felt like it was spinning too freely compared to the other times the boat cranked. NOTHING was happening. The starter was slinging the engine around just like it should with no results.

-After 5 minutes messing and worrying with it I finally pulled the spark arrestor off to confirm that it was getting fuel. You could clearly see the fuel pumping into the carb when you pumped the throttle. The choke butterfly was all the way open. We manually closed that and tried to start the engine with no results also. My brother in law manually pushed the pumper on the carb to pump fuel into it while I cranked on the key. The boat finally fired up after several rotations and pumps of fuel, it was hesitant for a few seconds but the idle smoothed out. I cut the engine off to re-assemble the spark arrestor and then fired it back up with no trouble

-The belts were squealing for about 20 seconds after getting underway but then the boat ran as good as I could ask it to. We high-tailed it back to the ramp and the boat did fine. Loaded the boat, killed the engine, re-fired with no trouble.

I am wondering what to replace from here. Last season I thought it was a spark issue but not I am second guessing. I know 0 about carbs but know that it is simple. You need air, fuel, spark... yesterday made me think there was not enough fuel. After reading several post on this board I was going to bring the boat home and test the voulume of the fuel pump.

Any suggestions? I plan on doing a new dist. cap, rotor, plugs, wires just because it seems like a good maintence idea for around $100+- . I think I can get a fuel pump for less than $100 also... but wanted to ask you guys before I went too far
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MikeW
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Joined: 01 May 2006
Posts: 680

PostPosted: Fri May 30, 2008 11:45 am    Post subject: 5.0/5.7 hard to start when hot Reply with quote

Hello, I doubt it's lack of fuel. Was it extremly hot at the lake?
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times2



Joined: 24 May 2008
Posts: 2
Location: Kentucky

PostPosted: Fri May 30, 2008 7:41 pm    Post subject: Vapor Lock Reply with quote

I believe this boat was Vapor Locked the other day. I re-routed the bilge blower hose and ran an extra vent hose to the engine bay... I took the boat out today and used a little more sense about what I was doing and the boat performed greata.

The temp last week was about 75* - today was closer to 85*
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MikeW
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Joined: 01 May 2006
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PostPosted: Mon Jun 02, 2008 3:29 pm    Post subject: Vapor Lock Reply with quote

That's why I asked about the temperature. Once the engine shuts down a lot of heat can build up. It's always a good idea to run the blower a few minutes before starting. Good luck!
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MD165250



Joined: 16 Sep 2011
Posts: 6

PostPosted: Fri Sep 16, 2011 5:55 am    Post subject: Hot start problem Reply with quote

Did this problem clear up for you? I have just started having a hot start problem the last two times out this summer. Cranks perfect cold, no pumping, no special exercises. Pull a skier strong then shut off for skier to board. After heat up period my ol' mercruiser 165 250 cid will not start until cool down. Impeller is new and boat maintains 145 degree while cruising for miles. It never gets too hot. Could this be electrical? When running it just purrs and once it starts again it purrs again. Thank you for any suggestions. I am re checking all fuel related issues. Very Happy
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MikeW
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Joined: 01 May 2006
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PostPosted: Fri Sep 16, 2011 7:22 am    Post subject: Reply with quote

It sounds like the heat build up in the manifold is causing the fuel to get hot and not want to ignite.
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MD165250



Joined: 16 Sep 2011
Posts: 6

PostPosted: Fri Sep 16, 2011 8:42 am    Post subject: vapor lock Reply with quote

.....as in vapor lock you mean MIke? ok. i will check again on the lake. the boat will not even heat up to temp on the muffs with cold water being injected. can you think of a reason it would just start this in the middle of the season? first few times out perfect. i will also try opening the engine compartment to let the heat out and running the vent fan to see if it makes a difference. Thanks Mike!
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MD165250



Joined: 16 Sep 2011
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PostPosted: Sat Sep 17, 2011 3:38 pm    Post subject: Hot start issue redefined Reply with quote

...so I checked everything fuel and ignition related, no vapor lock, fuel pump good, starter perfect, ran it up to cruising temp 140 degree in a barrel, stopped,started many times. Took it out on the lake this morning, cranked perfect, and ran it 10 miles and back to landing. turned it off and no start. checked for vapor lock, carb spraying perfect, temp perfect. Now I am thinking controls so I vigourously rotated,joggled the control back and forth, vroooom cranked fast. I ran the boat again the same 10 miles and back, RETURNED IT TO NEUTRAL, and noticed the boat was consistently shutting down when control was returned to neutral. ran it again, shut down again, return to neutral to crank, no crank, joggled the control, vrroooomm cranked again fast. This problem is without a doubt initiated when returning the gear to neutral from gear positions. I took it home and duplicated the problem every time in the yard. Run up to 120 temp, engage gear, back to neutral, immediate shutdown upon snapping in to neutral detente. no crank. joggle the control lever, Vrooooom, crank up and run great. Soooo, I disabled the 'no crank in gear' wire between control and ignition thinking there was wear in the control switch. Nope. It has to be something in the engine compartment that is shutting off ignition after running in gear and returning to neutral. Is there a wire back there? I traced the four power trim switch wires back and found the fourth purple one hanging loose. The other three are hooked to the trim pump and the trim works great. STUMPED! Is this quirky or what? The boat runs perfect at idle, troll speed, cruise,and wide open. shuts down immediate upon re engaging neutral. If I leave it alone after neutral click, NO CRANK. If I joggle the control lever it cranks right up EVERY TIME. Any one ever encounter this? So now not a hot start problem but rather a 'return to neutral control lever problem'Most appreciative , MD.
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MD165250



Joined: 16 Sep 2011
Posts: 6

PostPosted: Sun Sep 18, 2011 7:10 am    Post subject: update on Shift to neutral problem Reply with quote

I checked mercruiser sites and found there is a 'shift interupter' that releases the clutch dogs for shifting that will kill ignition if not working properly. Does anyone know where this switch is and if shift cables can affect it?
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MD165250



Joined: 16 Sep 2011
Posts: 6

PostPosted: Mon Sep 19, 2011 3:26 am    Post subject: questions answered Reply with quote

hello friends. i have seen this problem reported as hot start many times in the last week and please do not hesitate to post if your boat has similar symptoms. i learned alot in this troubleshoot about the shift interuppter switch and shift cable position. i will post resolution info. if you have a stall problem notice if it is happening when going in or out of gear. if your shift interuppter is left in the 'kill' position by your shift cable the boat will not start until you manage to move the cable and switch back to the correct ignition position. it sumulates a hot start problem because it can not happen in the yard on the muffs when not engaging the shift and prop. Hope this helps another frustrated boater:)
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MikeW
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Joined: 01 May 2006
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PostPosted: Mon Sep 19, 2011 7:40 am    Post subject: Reply with quote

Next time it is hot and won't start, by-pass the shift interrupt switch and see if that helps. If it is the problem you need to change the drive shift cable.
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MD165250



Joined: 16 Sep 2011
Posts: 6

PostPosted: Wed Sep 21, 2011 5:02 am    Post subject: switch bypass confirmed Reply with quote

with the switch bypassed it cranked reliably every time. then ran all over the lake with the' no start in gear' bypassed( i don't recommend leaving it this way, trouble shoot only) by leaving in forward gear and turning it off at switch. if you try this you will need a large lake with alot of open water at the launch as you will have no reverse or neutral. i just pushed off from dock and cranked after floating a good distance from the dock in foward.returning to dock i cut the motor at the switch and slow floated back to dock and landing. PROBLEM CONFIRMED! If cable can not be adjusted i am ordering new. GREAT to not be in the dark! Thanks all!
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