HorizonblueDK
Petty Officer 1st Class
- Joined
- May 27, 2010
- Messages
- 355
I have a 17 footer with an AQ170 engine (B30 straight six, triple Solex 44PAI ). I bought the boat as a project and finished it a couple of years ago. The boat is mostly used on the lakes nearby, which are no wake zones, so I hardly ever take it on plane. But sometimes when there are no canoes or other small crafts, I hammer the throttle. It has always been a struggle to get it on plane. It accelerates great until 2000 rpm, then it looses nearly all power and I have to be very gentle with the throttle, to avoid backfire.
I have tried much to resolve this problem, checking timing at 1000, 2000 & 3000 rpm, overhauling all carburetors, checking fuel pressure, checking acc pumping, running off a separate fuel tank. I installed a narrowband O2 sensor in the exhaust knee, so I could monitor what was going on. On the gauge I could see that when I hit 2000 rpm and the engine started to loose power, it was running lean.
Ok, so the engine needs fuel. Strange, the acc pumps worked fine. Even though the jets in the carburetor were the correct ones, I tried, just for fun, to replace the main jet with a larger one. That helped a little on the acceleration, but when running at slow speed, the engine nearly drowned.
So the other day I found an old Solex manual, which had an interesting drawing.
Quite logic, the fuel bowl must point towards the driving/sailing direction, to avoid fuel starvation, when "climbing". On the original Volvo installation the carburetors are oriented so the bowl is aft of the venturi, which is wrong according to this drawing.
The boat rises the nose quite a lot, when taking off, so I thought, well, lets rotate the carbs 180? and take a trip on the lake. And, Oh my, what a change, now the boat can take off, as it should.
Has anyone ever experienced this?
Can it really be, that Volvo didn't think about that, when building the B30, and I guess the B20 also?
I have tried much to resolve this problem, checking timing at 1000, 2000 & 3000 rpm, overhauling all carburetors, checking fuel pressure, checking acc pumping, running off a separate fuel tank. I installed a narrowband O2 sensor in the exhaust knee, so I could monitor what was going on. On the gauge I could see that when I hit 2000 rpm and the engine started to loose power, it was running lean.
Ok, so the engine needs fuel. Strange, the acc pumps worked fine. Even though the jets in the carburetor were the correct ones, I tried, just for fun, to replace the main jet with a larger one. That helped a little on the acceleration, but when running at slow speed, the engine nearly drowned.
So the other day I found an old Solex manual, which had an interesting drawing.
Quite logic, the fuel bowl must point towards the driving/sailing direction, to avoid fuel starvation, when "climbing". On the original Volvo installation the carburetors are oriented so the bowl is aft of the venturi, which is wrong according to this drawing.
The boat rises the nose quite a lot, when taking off, so I thought, well, lets rotate the carbs 180? and take a trip on the lake. And, Oh my, what a change, now the boat can take off, as it should.
Has anyone ever experienced this?
Can it really be, that Volvo didn't think about that, when building the B30, and I guess the B20 also?
