Port Engine Power Loss

[djmair]

Port Engine Power Loss

Logged this last year but still having problems. I have an 85, 10 Meter International. This is my 4th season and third with the same problem. I like the boat but am getting to the point of abandoning her.

Engine is fine to start and maintains power at idle. On the lake I lose revs and power on the port engine, now to the point that it will stall. After a cool down period I can start the engine and it will run at load for a short period but the problem will return. I am on the third mechanic and this is what has been done to date.
New Thermostat
New Electronic ignition
New Electric fuel pump
New Coil
New Wires
New gas line and fittings from tank plus all new filters
New check valve
Tune Up
Pressure check
Had a separate gas tank while on the water for direct feed into the carb for testing and had no problems with power.

All issues gas related seem to be removed except for intake tube, but I have 1 tank for both engines and the problem still exists with a full tank of gas. Removing this will be an issue as it is under the rear decking.

Can this be a heat issue or exhaust problem? Am I missing something?

[Diverted Income]

How about a fuel pressure gauge at the carb to prove lack of fuel? Put one on both engines to compare. Can prove or disprove then. Just a thought.

[mikeandanne]

Sorry to hear, these things are very frustrating--- maybe something simple----- if you hooked up your portable tank to the suction side of the new electric pump and had no problems then you can safely assume that the suction side of the port side fuel system is at fault in my opinion------- in that side of the lines do you have any rubber fuel hose that has not been changed and check for fittings that are leaking air back to where the stbd system joins---- sometimes the rubber hose will Delaminate and collapse on the inside which is not visible and make sure system is not undersized or has too many of those brass 90 elbows with the small line size inside ( I always drill the fittings out for better flow)---- well that is a start,you may have already done this but is all I can think of so far--- Mike

[ready123]

Anti siphon valve!
Sounds like that to me.... It is in the elbow at the top of the tank pickup tube. While servicing that blow air, med low pressure into the tank before replacing the check valve in case some crap is blocking the screen on the end of pickup.
If that solves it be aware you may have solids in the tank waiting to come back and clog those two locations!

[djmair]

Thanks for the replies:
New rubber gas line hose from the intake to the metal block hose has replaced the old copper to eliminate any cracks or damage.
Also replaced the check valve. The electric gas pump has been checked with a pressure gage and is providing proper psi.

[ready123]

Thanks for the replies:
New rubber gas line hose from the intake to the metal block hose has replaced the old copper to eliminate any cracks or damage.
Also replaced the check valve. The electric gas pump has been checked with a pressure gage and is providing proper psi.

Then I would look at the distributor... Sticking weights/springs affecting advance/retard. You did not have that in your new parts list.
Of course you might get right pressure at low volume if the screen on the end of pickup was partially blocked... Go there if you have a pickup for each engine, if not go to adv/retard, have you checked it on throttling up?

[todd brinkerhoff]

Both of my distributors were replaced prior to my purchase with similar issues. Now I'm in the process of having the carbs rebuilt. Welcome to 25 year old boats.

[mikeandanne]

Just remembered a problem I had with a previous boat that sounds just like yours,I had forgotten--- had qjet carbs and one engine would cut out under load---- well I took top off carb and the arms that pivot the metering rods from the I believe it was called the power valve were rusty ,resulting in jamming the mechanism--- cleaned it up and reassembled ,was ok till I got new part---- also check the fuel inlet well in the carb--- could be full of material from threads breaking down----I guess if you switched carbs from one to another engine you would find out if it was the carb or not---- Mike

[prowlersfish]

Don't forget that small fuel filter in the carb .

[Big D]

....Had a separate gas tank while on the water for direct feed into the carb for testing and had no problems with power.

BINGO!
The problem has to be with something that you by-passed. You said you went directly to the carb; you by-passed the pump too? Did they also do a vacuum test on the vacuum side of the pump? Except for the time you used the portable tank, were the engine hatches off for the other times/test runs also? What carb you using, what pump and rating?

[vabeach1234]

Check to see if the fuel tank pick up tube screen is clogged? Of course that involves removing it which you mentioned is difficult to get to. Maybe able to run a wire down the tube to push the screen off to allow more flow. Just a thought.

[Big D]

Check to see if the fuel tank pick up tube screen is clogged? Of course that involves removing it which you mentioned is difficult to get to. Maybe able to run a wire down the tube to push the screen off to allow more flow. Just a thought.

+1
make sure you're grounded...don't create a spark You can use a flexible semi ridgid plastic line to do this. Take the elbow off first. As I mentioned earlier, a vacuum tester in the suction side will tell you if you have a problem. Maximum allowable is 2 in. Hg. Any higher than this and it will likely cause problems. Because of this low spec, it's best to use a didgital vacuum gauge as they are more precise in this range. If nobody's done this, then they haven't diagnosed properly yet, they're simply taking shots in the dark and hoping one of them will solve the problem.

[djmair]

Thanks all

Going to try flexible tubing to see if there is a clog in the intake. I am also going to get a new or rebuilt carb and see if either issue is what is causing the problem

[ready123]

Thanks all

Going to try flexible tubing to see if there is a clog in the intake. I am also going to get a new or rebuilt carb and see if either issue is what is causing the problem

If it were me I would check the distributor first...... Your symptoms align with fuel starvation or distributor failing to change adv/retard. That is one important wearing part with age that your mechanic seems to have overlooked IMO.

[djmair]

I am going for a new carb and will be testing on lake with 2 mechanics on board.