ProV 150 rpm Drop

[Craig P]

I have an 86 ProV 150. It was running fine for about 15 minutes at about 4500 rpm. I noticed an rpm drop and then a power surge where the rpm picked back up. Then a gradual decrease in power to approx. 2000 rpm. No matter what position the stick was in, (full throttle, etc.) 2000 rpm was maximum. Only the green light on the tach was on. No indicator lights or beeps from the control box. When I got to shore, I checked the engine with my bare hand and it wasn’t overly hot, (felt normal, water stream was coming from the right side as normal). I have a Seloc manual that’s not very helpful or descriptive, can’t tell if I have temperature switches or temperature sensors in the heads. Any chance the control box located under the CDI unit could be causing my problem? Checked resistance from stator, blue wire to black with red stripe, 25 ohms. Black to red, 1,050 ohms. Any help would be appreciated.

[Hamfisted]

How old are the fuel pumps? Can you pump up the primer ball firm with the motor not running? If not you probably have a bad fuel pump(s). How old is the Racor filter? Any missing during the rpm reduction? Or is it just a general reduction with no buzzer horn? Your temp sensors should be at the top outboard side of each head. A quarter turn releases them and they pull out. You can test them in a pot of hot water with an ohm meter. Should be open (no continuity) below 180 degrees, and closed (continuity) between 180-195 and above...
These are just some things to look at.


-Mike

[Craig P]

Don't know the age of the pumps but the squeeze ball gets firm quickly and holds pressure. Don't know how old or what the Racor filter is, assuming it's inside the little clear plastic screw on bowl on the port side of the engine. Looks clean. No missing during rpm reduction. Just reduction to approx. 2000 rpm with no buzzer.

Went out today, engine fired up and idled perfectly. Ran around for approx. 30 minutes at 3000 rpm, didn't miss a beat. When I tried to kick the rpm up to 4500+, started getting feeling of reduction in power. Headed for shore to look things over, sat for about an hour, engine fired up with idle lever up. When idle lever was returned to the horizontal position, engine would not idle. Had to push idle lever down fast, shove in gear in order to get home. Ran fine at 3000 rpm but when attempting to kick it up to higher rpm's, got the feeling of loss of power. Thank you very much for the help.

[jb123]

sounds fuel related to me. i would try an auxillary gas tank and see if that makes a difference. it it was a heat issue, it would want to cool for atleast a minute then run well again and should be able to hit hi rpms.
sounds like it wants a high demand of fuel and its not receiving it and boggs back.
try an aux tank, check fuel pumps and clean carbs.
are your plugs new? wires ok?
also, it sounds as if you dont have a water seperator...you definately should.

[Craig P]

Still trying to fix the rpm drop. I installed new fuel pumps/gaskets, control unit, and thermo switches. Engine fired up ok, but was tough to keep running, (I assumed it was because of the weather approx. 45 degrees). Lifting the choke lever occasionally while engine was running helped. I let the engine run for a few minutes with fast idle lever up. It wasn't misfiring or popping back through the carburetor but it sounded like it wasn't runnig on all cylinders, (lifting the choke lever seemed to cause it to run properly). I can't get the engine to idle without having the fast idle lever raised. Acts like it's not getting the proper amount of fuel. Fuel pumps are brand new with new gaskets, no kinks in lines, no leaks and the squeeze ball is hard and there are no leaks when ball is squeezed forcefully. Thought I was going to solve my problem but looks like I've created a new one. Any help would be appreciated.

[jb123]

your cylinders want more fuel, choking gives it. clean your carbs, install a water seperator and then post your findings.

[Craig P]

Engine has a brand new water separator, filter on power head is clean, carburetors are clean (was idling fine until I installed the fuel pumps). No leakes anywhere, squeeze ball stays firm. I just checked the part number on the fuel pumps and they are the right ones for this motor, although the old ones had a casting number of 3J and the new ones 6A. Probably doesn't mean anything. This one's got me baffled to the point where I'm considering putting the old ones back to see if the problem goes away. Thanks for any and all help.

[slim]

did you put the gaskets behind the pumps? its possible that a piece of fuel hose got cut off and fell into the fuel line when pushing the hose over the new pump barbs and sometimes carb. inlet barbs also. i have seen some that were sharp and have seen pieces of hose behind the needle seat. even matched one up to the hose before. its not hard to do so maybe one cylinder isnt getting fuel. you said it was idleing before and not now?