New owner of 3.0 140hp Merc

[MtnBoater]

Hello,

Thanks in advance for any help! I just bought a 1985 Glastron-Conroy x17 with the Mercruiser 140 HP 3.0 4 cyl motor. Some questions...

1. At full throttle the boat tops out at 35-37 mph. I am at 5,000feet in elevation. Not sure what prop I have, but does this seem resonable?

2. Engine bogs when pulling a skier up, or when going from idle to "full speed ahead", checked all filters(which were dirty), and cleaned/replaced them. Fully disassembled carb and cleaned it all out thoroughly. Still bogs.

3. Possibly related to the bogging, the engine has stalled out twice and wouldn't restart. The second time I poured a little splash of gas into the carb and it fired up after some cranking(thank goodness). Does this sound like my fuel pumps going bad.

4. Do mechanical fuel pumps gradually go bad? Is it possible for the boat to run great sometimes, and like crap sometimes due to a failing pump?

Thanks again, I'm new to boats, but very mechanically inclined, and experienced with car and motorcycle engines, compared to some things I have worked on, this boat seems like a piece of cake!

And one final question: I paid $2,000, for the boat, needs some new vinyl, and this bogging issue corrected, but otherwise seems solid, good buy?

 

[mitchell7276]

Re: New owner of 3.0 140hp Merc

My boat is doing the same thing to the tee. I bought an 85 rinker this spring w/ a 120 merc 4cyl. The boat has ran fine the first few times out, but the last two times it bogs down under load. I got as far as pulling the fule filter in the carb and it was dirty. I cleaned it out and will be trying to take it out this weekend. I am clueless to this boat stuff and don't want to turn my $1500 rinker into a $5000 rinker.

 

[happycamper]

Re: New owner of 3.0 140hp Merc

MtnBoater,
If you're getting 35-37mph from a 3.0L at 5000', then you should be happy.

I have the same engine and I'm in CO too. I get about the same speed as you after I experimented with props (15x17 is optimum for me). In Arizona, we got about 41mph max using a 19 pitch.

Mine has been bogging down and hesitating lately when pulling a skier up. I plan to try a timing advance and look at the carb.

 

[capthook]

Re: New owner of 3.0 140hp Merc

There are several different things that could be going wrong here. Yes the pump can gradually let go. But there are a few other things as well. When was a tune up performed last: spark plugs, filters, water seperator if applicable. These all play serious roles. With the bogging it could be the accelarator pump or bad gas. You need to find DON S post on trouble shooting the fuel system I will see if I can find it. Here it is just copy and past into the address bar. http://forums.iboats.com/showthread.php?t=167561

 

[84 4 winns]

Re: New owner of 3.0 140hp Merc

hey all first post new boat owner. just bought an 84 4winns with a 140 hp inboard mercruiser this summer. sounds like we may have the same or similar engines. i take it out about once a week on average and the last two or three times i have noticed the same problem. full throttle is good for about a minute or two and then the rpms just slowly die. i've cruised around the forum here for a bit and came across this and other posts that describe similar problems and solutions. have you been able to pinpoint the problem since your last post? ive seen some suggestions about gimbal bearings and outdrives, but im not too familiar with boat mechanicals. these dont sound like issues i could address without a mechanic. carb looks good, wires and plugs were replaced in the early summer, original fuel pump. with my limited knowledge of marine engines this is about as far as ive been able to go on my own. any help would be greatly apprectiated.

 

[cheburashka]

Re: New owner of 3.0 140hp Merc

MtnBoater,

Mine has been bogging down and hesitating lately when pulling a skier up. I plan to try a timing advance and look at the carb.

Either the timing is right, or it isn't. Getting a better hole shot by advancing the timing beyond the recommended advance for your engine is very risky. You need to verify that the advance is working and that the timing is set to spec, but advancing the timing to correct a problem caused by something else is a good way to lose a head gasket.

 

[Haut Medoc]

Re: New owner of 3.0 140hp Merc

hey all first post new boat owner. just bought an 84 4winns with a 140 hp inboard mercruiser this summer. sounds like we may have the same or similar engines. i take it out about once a week on average and the last two or three times i have noticed the same problem. full throttle is good for about a minute or two and then the rpms just slowly die. i've cruised around the forum here for a bit and came across this and other posts that describe similar problems and solutions. have you been able to pinpoint the problem since your last post? ive seen some suggestions about gimbal bearings and outdrives, but im not too familiar with boat mechanicals. these dont sound like issues i could address without a mechanic. carb looks good, wires and plugs were replaced in the early summer, original fuel pump. with my limited knowledge of marine engines this is about as far as ive been able to go on my own. any help would be greatly apprectiated.

Welcome to iboats.....
Yours sounds like a fuel restiction of some sort.....You need to perform the tests outlined in Don s post above.....
Change the water separating fuel filter, if you do not have one, you should install one.....

 

[jedimaster]

Re: New owner of 3.0 140hp Merc

I can run 43 on gps with a 19 pitch cupped 3 blade alluminum at 5600 rpm's. I have an 88 glastron X17 Conroy. That works out to be a 12 percent slip rate witch is about right slightly on the good side from what I am told for the hull that we have, supposedly very effecient, although very old school looking. The theoretical max at 5600rpm's is 51mph,
I would think yor running a 17 pitch uncupped prop. and at 37 mph thats a 20 percent slip, also a decent slip rate, with a cupped 17 your speed should increase a bit.
When I was running my 17 I get out of the whole like a bullet, mine just doesn't idle well.

I am going to be trying a 5 blade cupped 21 pitch Stainless and a 4 blade 20 cupped stainless.
I think the 4 blade will be the best, I can get out of the whole pretty good with the 19 3 blade but I would like to drop my rpm's a bit more as I do alot of high speed cruising, the 4 blade 20 should be about the max before I can't get on plane.

I think your top speed is in the right range depending on your prop. The others here will be able to help you much more with your engine issues. I am still a noobie on that side struggling to cure my idle woes.

 

[MtnBoater]

Re: New owner of 3.0 140hp Merc

The problem was an easy and cheap fix. The accelerator pump wasn't doing it's job, so when I gassed it, it was only dribbling fuel in. I pulled the carb again, dissassemled and cleaned the accel pump, and also moved the linkage up one notch on the external lever on the carb. Now it sprays like a champ, and the boat jumps out of the water when I gas it, no hesitation whatsoever. Total cost: $4 for a new carb/intake gasket. The most I've spent on the boat yet!

One thing I did notice is that now the rpms are a little bit down at full throttle, and top speed is only 33 mph. I think it just needs a little more tinkering with the linkages, I don't think it is from moving the accelerator pump linkage up a notch, but I suppose it could be?? I rarely tear around the lake at full throttle anyways, so not a big deal.

Thanks for the replies, and for those with bogging off idle, check to make sure your accel. pump is spraying 2 nice strong streams down into the barrels, if not, there's your problem.

 

[84 4 winns]

Re: New owner of 3.0 140hp Merc

thanks a lot for your quick response haut medoc. that sounds like a relatively easy and inexpensive place to start. i considered a fuel problem initially but disregarded it because of the fact the boat would run so well initially then lose power. if the problem is with the fuel supply what would account for the fact that the boat runs so well initially then looses power slowly instead of consistently running poorly (ie if its not getting fuel why would it get fuel at first and then lose it instead of maintaining low fuel pressure from the beginning?) thanks again

 

[Haut Medoc]

Re: New owner of 3.0 140hp Merc

Yeah, I am thinking either a partially clogged pick up that sucks even more junk a& clogs more as you go, or a clogged fuel vent.......
One good test is to take a six gallon aux. tank & hook it up directly to the fuel pump.....
If your symptom goes away, you are at least pointed in the right direction......​

 

[Wotam]

Re: New owner of 3.0 140hp Merc

"I can run 43 on gps with a 19 pitch cupped 3 blade alluminum at 5600 rpm's."

No doubt someone will correct me if I'm wrong, but I think that is 1000 rpm over the design limit on a 3.0L 4 cyl GM.

Scotty to Kirk... 'She's gonna blow capn'... she canna take any more'.
Spock: Engine self destructing in 5..4..3...

 

[point92]

Re: New owner of 3.0 140hp Merc

I'm feeling pretty good about my 2007 185 Bayliner with the 3.0L merc. Yesterday I got 38.5 at 4800rpm going up river and 43.2 at the same rpm going down river on my gps. I'm at around 600' elevation.

 

[PowerAddict]

Re: New owner of 3.0 140hp Merc

thats 400 over according to my service manual giving the max. range 4200-4600.

(I've been reading the juicy information in there a lot lately)

 

[Haut Medoc]

Re: New owner of 3.0 140hp Merc

Welcome to iboats....
Sounds like yer doin' good!.......​

 

[jedimaster]

Re: New owner of 3.0 140hp Merc

oops yah meant to say 4600, not 5600. I think I my hands are screwed up, in another thread I said 3600 instead of 4600.