1989 Mercruiser 3.0 L, Mercarb, DDIS..bogs, no power

[beads8]

Last season it started to lose ability to pull tubers, skiers...It used to top our at about 40 MPH and have a pretty good hole shot. Before I put it in the water this year I had the carb rebuilt by a certified Mercruiser mecahnic. I changed plugs and wires. Still the same issue. I bypassed the fuel pump with a gravity fed setup and brand new fresh gas to eliminate the fuel pump as an issue and got the same response. The boat tops out and about 25 MPH when trimmed out, cannot pull a tuber and even when cruising at 25 MPH if I make a semi hard turn it bogs to 10-15mph. At 25 MPH the tach touches 4000 RPM's although it bounces so I probably need a new tach. To me it seems like a fuel system problem, but with the rebuilt carb and the fuel pump bypass setup I still get the same performance. Any suggestions would be greatly appreciated.

 

[beads8]

Re: 1989 Mercruiser 3.0 L, Mercarb, DDIS..bogs, no power

Any ideas? 18' Maxum by the way...

 

[Don S]

Re: 1989 Mercruiser 3.0 L, Mercarb, DDIS..bogs, no power

Disconnect the tach, and see if that is causing the problem.

Here is some troubleshooting information for the DDIS system.

View attachment DDIS.pdf

 

[beads8]

Re: 1989 Mercruiser 3.0 L, Mercarb, DDIS..bogs, no power

Thanks Don, I'll give the tach disconnection a try this weekend and report back.

 

[Secondwind218]

Re: 1989 Mercruiser 3.0 L, Mercarb, DDIS..bogs, no power

Going through the same issue this year. Ive been told to make sure timing is correct. To run through a compression test (make sure theres no weak cylinders), go through ignition, (plugs, wires, caps, rotor) and of course a rebuild of the carb which you have done. Ill keep you posted once figure out my problem. But same deal use to top 35 36 now cant get past 3900 rpms and tops at 25-28 mph's. good luck

 

[beads8]

Re: 1989 Mercruiser 3.0 L, Mercarb, DDIS..bogs, no power

Thanks secondwind...I need to check the timing for sure as it has not been checked in quite a while. The one thing that seems to me to indicate some type of fuel issue though is when I make a even semi sharp turns the boat almost comes to a stop and then takes 20-30 or more seconds with a straight ahead bearing to get back up to what is now my top end of 25 MPH. I have seen some posts that blame today's fuel blends that include ethanol as the culprit especially on a carburetor originally built for the blends used in the late 80's early 90's, and it is suggested that the ports that supply the fuel into the venturi cluster be drilled out to 1/16". I will add that to my list after doing some of the easier troubleshooting suggestions.

 

[maskedpretender]

Re: 1989 Mercruiser 3.0 L, Mercarb, DDIS..bogs, no power

Just a suggestion because I had a boat act like this a few years back, whet it ended up being is water between the hull and floor, slowed the boat down at top end and on curves, had to poke holes in the bilge area between the hull and floor and let drain, problem solved, back to full speed and pulling tubes

 

[beads8]

Re: 1989 Mercruiser 3.0 L, Mercarb, DDIS..bogs, no power

maskedpretender...thanks for the suggestion. That makes a lot of sense the more I think about it. The cover leaked this winter somehow (it was a brand new cover) the drain hole got plugged up, and the boat was full of water this spring, floor was mushy in areas etc. I will give it a try tomorrow. I went through quite a few troubleshooting suggestions today and didn't have much luck.

 

[beads8]

Re: 1989 Mercruiser 3.0 L, Mercarb, DDIS..bogs, no power

Well I made some progress...had to reset the choke, put on a water/fuel separator, checked timing (8 degrees dead on at 700 RPM's.) Took the kids tubing and still had a hard time getting on plane but once I did the boat ran pretty good. I had 2 teenage tubers, plus my wife and daughter in the boat with me so I was maxed out on weight. I still think I'm having a fuel related issue. A couple of times after stopping to pick up a fallen tuber...I could not get the boat over 12-15 MPH. I stopped once and took off the flame arresstor, checked the choke plate to make sure it was loose...I revved the boat to about 2500 RPM in neutral and checked the fuel supply flowing into the venturi's and could not see much if any fuel shooting out. How much should be flowing at that point? At any rate, Istarted pulling the tubers without the flame arrestor on and it took off and ran pretty well again...topping out at about 23-25 MPH and 4000 RPMs. When cornering, even slightly though I would lose speed and RPM's and it would take a straight shot for about 20-30 seconds to get back to speed. I checked the flame arrestor and it was very clean. I did drill a couple of pilot holes in the floor and discovered that the foam is wet...not sure that there is a ton of foam in a 17 ft Maxum but it is wet so probably is adding weight. The bottom line is that the boat doesn't perform anywhere near how it used to (but then again either do I). I'm sure age might have some part in the diminished performance...but not as much as I've encountered. Thanks in advance again for anymore suggestions.

 

[beads8]

Re: 1989 Mercruiser 3.0 L, Mercarb, DDIS..bogs, no power

Do the mechanical fuel pumps ever go bad? I will be checking that this weekend.

 

[jran]

Re: 1989 Mercruiser 3.0 L, Mercarb, DDIS..bogs, no power

I have a 1989 sea ray with a 3.0 mercruiser alpha 1 stern drive.....engine runs great just had it rebuilt....My problem is I have no speed..At 4000 rpm's I am at 25 mph with only myself in the boat.I've tried trimming up and down to find that sweet spot but speed tops out at about 25 mph with a 19p 3blade aluminum prop........Help

 

[beads8]

Re: 1989 Mercruiser 3.0 L, Mercarb, DDIS..bogs, no power

I have a 1989 sea ray with a 3.0 mercruiser alpha 1 stern drive.....engine runs great just had it rebuilt....My problem is I have no speed..At 4000 rpm's I am at 25 mph with only myself in the boat.I've tried trimming up and down to find that sweet spot but speed tops out at about 25 mph with a 19p 3blade aluminum prop........Help

jran...you should start a new thread rather than jump on mine...it can get confusing with guys trying to answer both our questions.

 

[86 century]

Re: 1989 Mercruiser 3.0 L, Mercarb, DDIS..bogs, no power

You are within 600rpm or so of Max for the eng if I'm not mistaken.

Have you checked the fuel filters on the carb and fuel pump.

 

[beads8]

Re: 1989 Mercruiser 3.0 L, Mercarb, DDIS..bogs, no power

You are within 600rpm or so of Max for the eng if I'm not mistaken.

Have you checked the fuel filters on the carb and fuel pump.

I replaced the fuel filter on the carb when it was rebuilt this spring and the fuel pump doesn't have one on mine. I did put a water fuel separator filter on it last week.

 

[beads8]

Re: 1989 Mercruiser 3.0 L, Mercarb, DDIS..bogs, no power

Checking the fuel filter at the carburetor today and found that it was in wrong. The spring was in AFTER the filter, and it is supposed go in first then the filter with the flat side against the spring. It seems like a small thing but the boat ran very well after that. Now I just need to figure out why it's so hard to start both warm and cold.

 

[beads8]

Re: 1989 Mercruiser 3.0 L, Mercarb, DDIS..bogs, no power

Well back to the drawing board again...boat ran very well compared to how it was running...BUT I still have an issue when pulling a tuber and make a sharp turn as in a "doughnut" the RPM's drop and it's hard to immediately get them back. Even when going straight after the slow down...it seems that the carb is starved for fuel. I also get a flooding condition when idling. Also to start the boat in both a warm and cold condition I need to have the throttle wide open and crank for a very long time before it starts. To me that indicates a flooding condition. Could the drop in RPM's on sharp turns also be caused by flooding, even though it would seem more like a lean out condition? I'm getting pretty frustrated at this point. Thanks in advance for any suggestions...

 

[beads8]

Re: 1989 Mercruiser 3.0 L, Mercarb, DDIS..bogs, no power

Well back to the drawing board again...boat ran very well compared to how it was running...BUT I still have an issue when pulling a tuber and make a sharp turn as in a "doughnut" the RPM's drop and it's hard to immediately get them back. Even when going straight after the slow down...it seems that the carb is starved for fuel. I also get a flooding condition when idling. Also to start the boat in both a warm and cold condition I need to have the throttle wide open and crank for a very long time before it starts. To me that indicates a flooding condition. Could the drop in RPM's on sharp turns also be caused by flooding, even though it would seem more like a lean out condition? I'm getting pretty frustrated at this point. Thanks in advance for any suggestions...

 

[beads8]

Re: 1989 Mercruiser 3.0 L, Mercarb, DDIS..bogs, no power

Hi Don,
I finally had some time to start going through your list of possible causes ...unfortunately or fortunately I guess depending what I end up finding out, I have found the/an issue at #9 compression. Cylinder #1 = 0, 2=60, 3= 90, 4=0. I can't believe the boat has even run at all given those numbers. I verified my compression test tool was working on my 25 HP Mariner that registered 130psi on both cylinders. Looking through some posts it seems that numbers like this indicate a total loss. It really hadn't occurred to me that I could have a compression issue as I have been diligent with maintenance as far as oil changes, winterizing, cooling system etc. since buying the boat brand new way back in 1989. Is there any hope that it could be "just" a blown head gasket or a valves issue, or am I pretty much looking at a total rebuild? Thanks in advance for your thoughts.

 

[beads8]

Re: 1989 Mercruiser 3.0 L, Mercarb, DDIS..bogs, no power

bump...anything?

 

[starcrafter65]

Re: 1989 Mercruiser 3.0 L, Mercarb, DDIS..bogs, no power

Where are you located? I would just look for a donor motor I did with no problems. Or consider getting a short block for
I think 1200