Guests - If You want access to member only forums on HSO. You will gain access only when you sign-in or Sign-Up on HotSpotOutdoors.

It's easy - LOOK UPPER right menu.

Sign in to follow this  
Followers 0
ewirz

'98 Merc 75 hp question

12 posts in this topic

Hello all. I have the motor listed above. I just had it rebuilt - new rings etc. I just got done with the breakin period. The mechanic had retarded the timing on it I guess to keep from accelerating hard. During the breakin, it ran fine other than it ran rough and hesitated a little while accelerating, but once at WOT it was fine (mechanic said that would be normal). I re-timed it (5 deg at idle and 18 at WOT) and ran it last night. Still hesitating when acceleration. Whats the deal? Did I not time it right? Carb need adjusting?

Shop tach showed 800-900rpm idle, 5100rpm @ WOT with 13.24x17 prop on Alumacraft 175 tourny pro.

It's not the fuel line (brand new), also had the fuel pump rebuilt, no water in fuel...Thoughts?

Thanks for the help

ERW

Share this post


Link to post
Share on other sites

If you choke it during acceleration (when it hesitates) does it pickup or bog out?

How about long runs at idle? Does the motor load up? I'm wondering if the carb settings aren't quite right and the motor is loading up prior to take off or to lean and starving for gas at acceleration.

When was the last time you had your carbs gone through? Did you run gas stabilizer through the motor prior to startup?

marine_man

Share this post


Link to post
Share on other sites

I didn't try choking it but I will and report back.

I had it idling for a long run last night (trolling), and didn't seem to be loaded at all (too lean?)

I cleaned the carbs this spring top to bottom. They were pretty clean. I think the mechanic re-adjusted them while he had it and he's not known for doing a good job in that department. I always run stabilizer.

I'll try choking it and re-adjust the carbs and let you know. Thanks for the help MM.

ERW

Share this post


Link to post
Share on other sites

Well, ran the boat quite a bit this weekend.

This is what I observed. If the motor was realatively cold, it hesitated accelerating, choking and/or squeezing the bulb only made it worse. If the motor was warm (like I had been trolling or driving around) it did not hesitate.

Manual says 7/8-1 3/8 turn out on the idle screw. I started at 1 and tried at 1 1/4 (on all three cylinders of course), no difference.

Carb cleaning in order?

ERW

Share this post


Link to post
Share on other sites

Did you try 7/8?

When you say cold, can you elaborate? Like right after startup?

Having to warm a motor up prior to take off is not that un heard off, although not always the norm on a 2 stroke.

marine_man

Share this post


Link to post
Share on other sites

I didn't try 7/8 but next time out I can.

I guess I use cold a little loose. I always let it warm up for a good couple minutes at idle or just above before hammering it.

Before the rebuild, never had this issue. Cold or been running for a while, it always jumped right out of the water, just seems odd.

ERW

Share this post


Link to post
Share on other sites

Just another thought....

If its running too rich at 1 or 1 1/4 turns, would it still hesitate accelerating? Also would it idle a little rough and fast?

It just seems like if the gas was a little rich while accelerating wouldn't cause the hesitation but would cause a rough idle and loading up....

Thinking out loud I guess. Thanks again for the help. I'll giver' a shot at 7/8 and see what happends.

ERW

Share this post


Link to post
Share on other sites

I would think that it may load up, which you said it wasn't, but I'd like to exhaust that chance first...

Where did you get your timing spec from? Unfortunately I don't have it, but it might be worth double-checking it.

marine_man

Share this post


Link to post
Share on other sites

I got the timing specs from the Clymers repair manual. I also double checked the id plate on the cylinder head, both the same.

5 deg idle and 18 @ wot.

Share this post


Link to post
Share on other sites

I think MM is pointing you in the right direction. Lean out the idle to 7/8th.

Share this post


Link to post
Share on other sites

Just an update and another questions....

I triple checked the timing and I had it right. Although I forgot to set it at cranking speed, which helped (I think). I also found that the mechanic(if you could call him that) really screwed up on the throttle link and syc. I also found a few gas line clamps missing between the carbs that may have been leaking. After fixing all that, it runs like a top.

So the question....

Right now I'm running a 13.25x 17 aluminum prop on a '99 tournament pro 175. RPMs at WOT are about 5100 and getting ~33mph by my self, 1/2 tank and fishing gear. Hole shot ok but would like a little more speed if possible. I have a 19 pitch and get 34-35 but RPMs are around 4950. Can I move motor up a hole (on 2nd from top) or should I be happy with what I got?

Thanks again for all the help.

ERW

Share this post


Link to post
Share on other sites
Guest
This topic is now closed to further replies.
Sign in to follow this  
Followers 0



  • Posts

    • After a quarter century in the construction sector I learned you should take your budget, double it and add another 10%. That gets most people in the ballpark anyway lol. 
    • You didn't even understand the question Junior. Do we need to get you a translator? 
    •   And then what? There's a saying that goes, "Be careful what you wish for. You just might get it."   You have a country of 300 some million individuals and a good number of that all have different ideas how to so call fix this. That's why we are set up as a representative republic and not a democracy.   You seem to be assuming most people will see things your way

    • Look my very own internet stalker making memes about me, such a proud day.

    • I guess the question is when are we going to get pizzed off enough to do something about it? Guess we aren't there yet.
    •   Hi guys ... Everyone was very helpful last year with what line to use ect...   As I was a fairly new Bass fisherman.  Had a great last open water season as did great with Texas rigs with variety of Senko's.  Also started throwing frogs with 50# power pro with 7'6" med Heavy rod ... wow is that fun!!   What brand is every throwing or like?   I'm going to try the Bobby's Perfect Frog this year  by Snag Proof.  I threw the Booya's this last year and that is a rush.  Can't wait for some basin times!!
    •   Yep, had to fix a few of those switches and tell the wife and kids to let the motor stop before pounding it in reverse!!
    • Kind of crude image but here is what I'm looking at.
    • Access is in the middle but I'm not overly concerned with that.  I can seal it up and cut a new one.  I'm thinking about slide channels mounted on the wall with a steel or aluminum frame mounted to the channels that can slide up and down with a electric winch routed through a couple pulleys. 
    •   You and Bearsheet.................blame everyone but yourselves.  All you those grueling hours you 2 spent in Sillytown advocating for Gary "Hillary is great" Johnson.   #victim #noonegetsitbutyou
  • Our Sponsors