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View Full Version : Totally confused on engine issue now


dgunthert
06-23-2008, 01:24 PM
1997 Prostar 205, TBI

I've been trying to diagnose a performance issue for a while now. Boat runs fine at first, but after 10-20 minutes it starts losing power until it will barely idle under load. Revs fine in neutral, but put it in gear and it bogs down. Pull up on the throttle a little and it will surge a bit before bogging down again at the new setting.

So far, I've replaced the fuel filter, which had some water in it, drained the tank and refilled it, replaced the plugs, cap, rotor, and fuel pressure regulator diaphragm. I've also got a couple of bottles of Techron in the tank to try and flush anything that may be in the injectors. I really thought water in the line was the issue, but I can't see how any of it is left.

I spoke to a mechanic who suggested checking most of the above. He also brought up the possibility of overheating. The temp gauge on the dash seems to work, as it will gradually rise from the peg and then hover around 140-150. However, he and others have said that I should be able to put my hand on the risers with no problem. After running the engine for a bit, though, they're too hot to touch for more than 3-4 seconds.

I've checked the impeller, the filter where the line for the transmission cooler branches, and the hoses as best I can. I haven't replaced the thermostat, but I did remove it and nothing changed. If anything, that should make the engine run too cool, right? The engine is taking just about all of the water I can supply through a garden hose via the fake a lake and it's all coming out the exhaust.

Are the risers a red herring in relation to my original issue or should I be concerned about their temperature?

sdesmond
06-23-2008, 01:32 PM
Did you check the screen on the inlit to the fuel pump? I hade a power loss problem and come to find it this was clogged with tons of carpet fibers. This was the last thing I checked and it ended up being the problem. I cleaned it up real good and it cured the problem.

Here is a thread i started about my problem. http://www.tmcowners.com/teamtalk/showthread.php?t=23701

rob935
06-23-2008, 05:13 PM
is your boat fuel injected or carb , if it has a carb you may have some dirt or blockage in it ??

dgunthert
06-23-2008, 05:30 PM
It has throttle body injection.

I've checked the pump as well. Besides, it doesn't seem that clogging would explain the gradual loss of power after initially being okay.

rob935
06-23-2008, 05:45 PM
in that case your problem may be electrical , what kind of shape are the plug leads in ??

rob935
06-23-2008, 05:54 PM
as for the risers i reckon its a different issiue , do they get as hot when the boat is in water or just when using the fake a lake as it will draw in more water when in water and cool much better . any boat i have had in the past has always had risers that were hot to the touch so personally wouldnt worry about that .

sdesmond
06-23-2008, 06:36 PM
It has throttle body injection.

I've checked the pump as well. Besides, it doesn't seem that clogging would explain the gradual loss of power after initially being okay.

Mine would srtart out fine and then gradually lose power. It ended up being the pump. Guess your situation is different. Have you checked your fuel pressure?

GuitsBoy
06-23-2008, 06:42 PM
Yeah, ditto on the pump. Especially in cars when a fuel pump starts dying, it typically starts out with acceptable pressure, but as it heats up, it loses pressure. Leave a fuel gauge hooked up to it while it shows the symptoms. Chances are it'll show you're a lot lower than when you first started it up. Running your tank below 1/4 tank and theres not enough fuel to effectively cool the pump, and it starts to overheat and reduces its life. Keep your car and boat tank filled often, and you reduce your risk.

dgunthert
06-24-2008, 11:46 AM
So a couple of follow up questions:

What should the fuel pressure be? I've read conflicting posts on this.
If it needs replacement, is this the right pump? http://www.skidim.com/prodinfo.asp?number=RA080023

Chicago190
06-24-2008, 11:56 AM
So a couple of follow up questions:

What should the fuel pressure be? I've read conflicting posts on this.
If it needs replacement, is this the right pump? http://www.skidim.com/prodinfo.asp?number=RA080023

According to my 1996 manual its 30 PSI.

dgunthert
06-25-2008, 11:53 AM
Still hoping for an answer on the pump itself. The one I posted above looks just like the one in the boat, but obviously I want to be sure before shelling out over $300.

Homer
06-28-2008, 01:46 PM
Definatley sounds like some junk stuck in the bottom of the fuel pump screen. You do have to take all fitting off the bottom to check it. You should have a metal screen on the bottom of the inlet side of the the pump. If there is any junk stuck in it it will give you the symptoms that you are experiencing.

Storm861triple
06-30-2008, 01:20 AM
Put a fuel pressure gauge on it and that will answer ALL your questions about the pump. :)

Thrall
06-30-2008, 01:40 AM
According to my 1996 manual its 30 PSI.
Where did you get a service manual? I'd sure like to have one before my boat gets too obsolete!

That's correct. Sounds like the fuel pump is dying. Like Storm said, hook up a gauge to it before spending the money on a new pump though.

Storm861triple
06-30-2008, 02:05 AM
One additional tid-bit; the actual FP spec isn't THAT important in this case, (though it would be nice to know). When you start the boat cold, and it's running fine, note the pressure. Then when you start seeing the symtoms, note the pressure again. When it gets to the point that that it will barely idle under load, note the pressure again. If the fuel system is at fault, your pressure will have fallen, and it should not.

-Tom

Chicago190
06-30-2008, 12:37 PM
Where did you get a service manual? I'd sure like to have one before my boat gets too obsolete!

That's correct. Sounds like the fuel pump is dying. Like Storm said, hook up a gauge to it before spending the money on a new pump though.

No service manual, but its listed in the specifications section of the MC manual and Indmar manual.

There is this, but I don't know if its any good: http://www.amazon.com/Indmar-1983-2003-Clymer-Marine-Repair/dp/0892879769/ref=pd_bbs_sr_1?ie=UTF8&s=books&qid=1214840055&sr=8-1

JimN
06-30-2008, 12:57 PM
Test the pressure at Key ON, Idle, 2000RPM and WOT- this is standard MC recommended testing procedure. If there's no Shrader valve on the fuel line, remove the the one that attaches to the throttle body and have a valve installed. DO NOT USE RUBBER HOSE AND HOSE CLAMPS!

The pressure should be basically constant, with slight dips when the throttle is advanced hard at speed. Otherwise, whatever you see at key ON is what you should see at high RPM, when fuel delivery is most important.

Actually measuring the fuel pressure is the only way to tell if a pump is bad. Anything else is just guessing.