Some Mercruiser 3.0 questions

[Chemdawg]

Hello everyone. I've been reading a lot of things from different posts throughout the internet, but I decided it would be best to start my own thread and ask my questions here.

I have a 1987 Arrow Glass Carisma 175, with a 3.0L mercruiser engine. When I got this boat, it was a basket case. The motor runs great now for the most part. Good oil pressure and the temp is good. NO water in oil, etc... Compression is excellent also.

The question I have is when I go to take off, if I punch the throttle a bit, it hesitates a little, but within a second, or so it will take off. Now I thought this hesitation was a fuel related issue, but I'm running about 5.5 PSI of fuel pressure to the Mercarb. I put new plugs in when I got it, but I have NEVER changed the Points, Condenser, Distributor Cap, or wires. I ordered a tuneup kit witch came with it all but the wires from right here on the site. What other things can I check that would cause this hesitation?

Thanks in advance.

Pat

 

[alldodge]

Hello everyone. I've been reading a lot of things from different posts throughout the internet, but I decided it would be best to start my own thread and ask my questions here.

I have a 1987 Arrow Glass Carisma 175, with a 3.0L mercruiser engine. When I got this boat, it was a basket case. The motor runs great now for the most part. Good oil pressure and the temp is good. NO water in oil, etc... Compression is excellent also.

The question I have is when I go to take off, if I punch the throttle a bit, it hesitates a little, but within a second, or so it will take off. Now I thought this hesitation was a fuel related issue, but I'm running about 5.5 PSI of fuel pressure to the Mercarb. I put new plugs in when I got it, but I have NEVER changed the Points, Condenser, Distributor Cap, or wires. I ordered a tuneup kit witch came with it all but the wires from right here on the site. What other things can I check that would cause this hesitation?

Thanks in advance.

Pat

Looks like you need a new accelerator pump in the carb. With the engine off, have someone push the throttle forward easy and see if you see a stead stream of full. My guess is the first part of the throttle is not much squirting going on. Pick up a kit with one and give it a good cleaning

 

[Chemdawg]

Thanks for that response Alldodge. That was one of the first things I checked. I removed the linkage from the carb so I could actuate the carb and see what was going on, and the two streams looked good. Of course till it ran out of fuel. Cause motor wasn't running.

I pulled the distributor apart so I could have a good look, and it's pretty dirty, and whatnot. I already have the points and condenser on order, and the cap comes with it. However, I was pulling the mechanical advance apart to clean it, and lost one of the springs. Where can I get a replacement spring from???

 

[airshot]

Not sure where to get the springs but I am quite sure you will find them as this is a popular motor. Sounds like you are on the right track..getting everything clean and functioning properly. I agree on the acc pump and I might add to check the timing as well as this may also cause hesitation if retarded. Also take a look at prop pitch and engine rpm at wot and be sure they fall within mfgs recommendations, of course you will need to get the engine running at its peak before checking wot.
Good luck and welcome aboard

 

[Moonstruck]

I had this engine in a year 2000 boat. There was always a flat spot in the power at 2800 RPM. I would just push the throttle through it and by 2850 it was all good. As this was a common engine in boats where I am, I began asking other owners of the same engine & similar year if they had a similar problem. Five out of five people said that they had the same condition in their engine. They all said that after powering through the flat spot everything ran great. I just learned to anticipate it and enjoy the boat. Just my $0.02...

 

[fishrdan]

As said earlier, it sounds like an accelerator pump problem to me. You said you saw 2 streams of fuel while operating the throttle, but did you try moving the carb's throttle slowly, and also fast?

To overcome the issue of emptying the carb by operating the throttle (acc pump sucking the bowl dry) fill a mustard bottle with fuel and re-fill the carb's bowl via the vent tube. Dollar stores have mustard/ketchup bottles for,,,, a buck.

Does your Mercarb had (3) different linkage positions for the acc pump? I haven't worked on a Mercarb, but understand the different positions will give different acc pump shot volumes.

 

[Chemdawg]

Thanks to all for those responses. The springs I think I can get at like advance auto parts, or someplace like that. They are a common size from what I understand. If not, maybe my local boat shop might have them. I know it cannot hurt to rebuild the distributor, because who knows when the last time it was done. I will eventually go to an electronic setup, but I've already dumped enough into it this year, so rebuilding the points/condenser/cap will work for now.

I'm going to dig into the carb a little more. I did NOT rebuild it. All I did was pulled it off, and dunked it into a bucket of carb cleaner for a while, and blew it out with air. It has ran ok since then though. This problem started within the last couple of times I've taken it out. But I'm going to look into it some more and see.

 

[MikDee]

Thanks to all for those responses. The springs I think I can get at like advance auto parts, or someplace like that. They are a common size from what I understand. If not, maybe my local boat shop might have them. I know it cannot hurt to rebuild the distributor, because who knows when the last time it was done. I will eventually go to an electronic setup, but I've already dumped enough into it this year, so rebuilding the points/condenser/cap will work for now.

I'm going to dig into the carb a little more. I did NOT rebuild it. All I did was pulled it off, and dunked it into a bucket of carb cleaner for a while, and blew it out with air. It has ran ok since then though. This problem started within the last couple of times I've taken it out. But I'm going to look into it some more and see.

You're doing the right thing Chemdawg! Speed shops used to carry the Dist. springs with 3 different versions to set up quicker advance in a little fairly cheap pkge. One of these sets may work for you? If you can soak the carb overnight, it would really help. Keep up the good work.