Originally Posted by Cheechako
I'm just too far behind on all the details. Maybe if you can put a short synopsis of the problems and trials to solve them, more people will respond. Difficult to catch up at this point.
"When it slows down opening the engine hatch clears it within minutes (except one time it didn't because it was warmer outside).
I am not sure if the exhaust manifolds are clogged (would thin ECM would have thrown an overheat code since it measures that temp) or how I would determine that. "
How many electronic controls are on the boat? is it a newer boat with those? Maybe there is something in the "black box" causing it when ambient heat rises?
On a normal "old school" engine, it doesn't care about much but it's internal operating temp.
Is the engine room vented so it can get air?
My last powerboat was a 24 foot with a 305 GM engine. Two people on board was much different in power than 4 people on board for sure. Surprising.
Does your fuel line from the tank have a backflow check valve? They are required for outboards but some makers just put them in anyway. I ran into an issue once with those not supplying enough fuel to the engine when it warmed up, on an engine with a "black box".
I agree that's a great long thread! It's a 2001 Sea Ray
bowrider. It has an ECM that can store lots of information such as manifold temperature, guardian alarm
(apparently my MEFI version doesn't even have a guardian alarm
though), and other types of sensors and warnings. As far as electronics
it has the basic gauges (temp, oil
etc) at the helm
but nothing fancy. I am thinking about adding a Fox Marine
gateway device that will allow me to view ECM information on my phone
via bluetooth and to my chartplotter
not only for this issue but may be helpful in the future.
Yes I will give you a basic summary of events
Boat slows down after running 30 minutes to an hour at RPM above 3100. When it slows it downs down to 2500 and wont go faster no matter how far throttle is advanced and stays at 2500 all the way home.
Mechanic believes its likely fuel tank
vent, clears it out - Issue still occurs
He checks ECM codes as he runs and when it fails it doesn't throw any codes. Checks and adjusts oil
pressure to no avail. Believes it may be MAP sensor, replaced it and still having trouble.
He hooks up a portable gas tank - Issue still occurs
He hooks up a boat-in-a-box - basically it lets him bypass boats wiring
harness to rule
issues - for first time issue does not occur.
When he was hooking up boat-in-a-box the hatch had to be opened so he suspected a thermal issue. He goes back to original boat wiring
and runs it until it happens again and when it does he opens hatch. Within minutes for the first time the issue clears (normally it would be stuck at 2500 for 1/2 hour or more at that point I would be heading home not sure if its going to stall).
He tries replacing a few more parts
before he concludes it might be ECM but wants to test it first. Mefiburn company that rebuilds ECMs say that he should run boat and if there's an issue with ECM getting warm if he sprays it with freeze spray that will confirm if its a problem with ECM. He sprays it and it does nothing and tried spraying other parts
. At this point he says there's a coil that is inside the distributor box that could be the cause and he replaces the coil. At this point its getting colder and rougher and harder to test but have not noticed issue yet still uncertain.
As far as the engine room being vented there are two vent hoses on port side and 2 on starboard under hatch. Should it be vented in any other way except through the exhaust going out of the stern? He also bypassed the possibility of a fuel issue when he hooked up a portable tank and bypassed all electrical
systems with his boat-in-a-box.
So opening the hatch is the only thing that is fixing it and it's not a fuel or electrical issue.