Store Links Mobile - Shop Now

Announcement

Collapse

Help Tip: If you have a question that has not been answered to your satisfaction in the archives, it is always best to start a new thread of your own. By starting your own thread, you will receive the maximum number of views by forum members.

Below are some additional forum policies in hopes of all iboats members will follow, Thank you.

1. Please do not reply to old topics or hijack existing topics. Old topics of a technical nature are like a library book, Please do not write in them.

2. Old topics should be considered archives and used for reference only. Please do not reply to them.

3. Do not take over someone elseís topic (aka hijack) with your own question, even if it is similar. If you have a question that has not been covered to your satisfaction in the archives, it is always best to start a new topic of your own.

4. If you have a question for the original poster (OP) and the topic is over 30 days old, send the OP a PM, he may not even visit the forums any longer, or may not notice your question in the old topic.

5. By starting your own topic, you will receive the maximum number of views by forum helpers that may not even notice your question when itís posted at the end of someone elseís topic. And those answers will be specific to your particular issue.

6. Please do not post to topics that have been inactive for more than 3 months unless you are the original poster. We have very active forums and any topic that remains inactive for that long should be considered "dead". It is especially confusing when there is an entirely new question posted to an old topic.

7. Posting at the end of any topic is considered to be hijacking the original posters topic which in turn subjects the topic to be closed if it continues to happen thus not making it fair to the original poster in the future had for some reason he/she needed to return for additional information or provide an update of the problem solved which is always welcomed within a reasonable amount of time frame.

8. Please note that you should see a red banner pop up near the bottom of each inactive topic asking you not to reply to old topics. The Red banner will read: Please note this topic has been inactive for 90 days. For the best results, please start a new topic.

Thank you all in advance for doing your part in helping iboats run a smooth ship.

Additional forum rules linked below.
http://forums.iboats.com/forum-rules-guidelines-405/
See more
See less

Low RPMs (probably not prop-related)

Collapse
X
  • Filter
  • Time
  • Show
Clear All
new posts

  • Low RPMs (probably not prop-related)

    Alright guys, question for you. I have a 2002 F115 that's ran flawlessly for its entire life, I think it's not started twice in 15 years, and otherwise I've had zero problems with it. Except....

    For a number of years the RPMs have been low. Anywhere from 4500-5200 WOT. It's actually my father's boat (although I'm the only one who uses it), which is why I can't say for sure how long it's been like this. I only started paying attention to the RPMs about five years ago, although I always remember it running in the low-mid 30's as far as WOT MPH goes, so it's probably been an issue for quite awhile. Having said that, again I'd like to stress that we haven't had any other problems with the motor. Over the last couple years I've played with props, sticking with the cheaper Yamaha OEM aluminum ones mainly because of price, and the knowledge that I might have to try a few. Its had 19, 17, and 15 pitch props on it, which got me anywhere from 4800-5200 max RPMs, at its best performance. I will say that it tends to dog down in rough conditions or with a heavy load, more than I would think it should, although that's just speculation on my end. For example, in 2-4 foot rollers, I'm only seeing low 4000's and a speed of 25-29 mph. If I rev it down and then back up, I can usually get higher RPMs until it hits a decent sized wave. I know it's hard to qualify "rough water", but I do have extensive experience on the water, and I can tell you I'm not running it anywhere near its limit for what it can handle. I've been in water that was too nasty to get any decent speed going, and the boat seems sluggish at conditions below that level. I would say it averages around 4900-5100 RPMs in decent conditions at WOT, trying to trim it up to get it past the very low 5000's just causes the prop to blow out.

    The strangest thing to me is that other than the RPM/speed issues, the motor has given us no trouble at all, I'm not seeing any other symptoms. I'll be the first to admit I don't have much mechanical experience, and my dad is the type who waits until there's a problem, then drops it off at the mechanic and pays whatever they tell him to, so feel free to dumb down any answers or advice or tips you guys have! I've heard a bit about potentially clogged injectors or VTS being a possible culprit? For the record, it's hung on a 2002 Lund Fisherman 1700. Thanks for any help you guys can provide!
    Last edited by TMF89; December 5th, 2017, 05:49 PM.

  • #2
    welcome aboard

    first and foremost, do a compression check (guides in the stickies)

    check out the color of your plugs

    next, check out the guides in the stickies for low WOT

    a good marina will have test props (no need to buy to test)
    1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - http://forums.iboats.com/forum/owner...988-rogue-2420

    Past Boats
    1970 Wooster Hellion - Merc 9.8
    2002 SeaRay 190BR - 5.0 - A1G2 - "Cheasheads in Paradise"
    1984 Avanti 170DLI -3.0 stringer- "Ship Happens"

    What’s behind you doesn’t matter.Enzo Ferrari

    Comment


    • #3
      Scott, thanks for the response! I'm planning on changing the oil/gear lube, fuel filter, and plugs this weekend anyway in preparation for winter, so I'll try to do the compression test then. I saw the thread you mentioned, and the only question I have is on the 4th step, where it says to rig a jumper to engage the starter solenoid without using the ignition. Any chance you could expand on that? Also, I wasn't able to find the thread discussing low RPMs at WOT, I did find one in the same forum as the compression guide that went over how an outboard should perform at WOT, generally speaking, but that's about it. Thanks again for your help!

      Comment


      • #4
        If you dont know how to jumper a starter solenoid, step away from the tools and get assistance. it is autos class 101 and basic electrical 101

        many times you can even use a screwdriver to jumper it.

        http://forums.iboats.com/forum/engin...ses-of-low-wot

        http://forums.iboats.com/forum/engin...-questions-faq

        1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - http://forums.iboats.com/forum/owner...988-rogue-2420

        Past Boats
        1970 Wooster Hellion - Merc 9.8
        2002 SeaRay 190BR - 5.0 - A1G2 - "Cheasheads in Paradise"
        1984 Avanti 170DLI -3.0 stringer- "Ship Happens"

        What’s behind you doesn’t matter.Enzo Ferrari

        Comment


        • #5
          I know the idea behind jumping the starter, but again, I haven't had the opportunity to take Auto or Electrical 101, that's why I'm here asking these novice questions. I guess my question would be more why do it that way, as opposed to just using the ignition? Simply because it's easier for one person to do it from that position?

          Comment


          • #6
            because by using the ignition, you run the risk of fire, damage to your ignition and a really good spark giving you a jolt.

            simply cranking the motor by jumping the starter, simply spins the motor
            1988 Cruisers Rogue 2420 -VP 290 DP now powered by custom 468 - http://forums.iboats.com/forum/owner...988-rogue-2420

            Past Boats
            1970 Wooster Hellion - Merc 9.8
            2002 SeaRay 190BR - 5.0 - A1G2 - "Cheasheads in Paradise"
            1984 Avanti 170DLI -3.0 stringer- "Ship Happens"

            What’s behind you doesn’t matter.Enzo Ferrari

            Comment


            • #7
              a service manual for your motor will give the steps and spec for testing the systems and also tell you what test equipment is needed to do the testing

              guessing and changing parts and hoping get expensive quickly

              Comment


              • #8
                Sign up today
                Thanks for the info, I didn't realize that it would put a ton of stress on the ignition system. And I don't really plan on guessing and swapping parts, I'm just trying to do what diagnostic work I can. I DO know how to change spark plugs, the injectors haven't been cleaned/swapped in...well possibly ever, so I plan on removing them and sending them to Injector Man, and the compression test seems like a pretty straightforward way to save a couple hundred $$$, since if I take it in to a shop, I'm sure they'd want to run that test anyway. Basically if the plugs and injectors don't fix it, I plan on bringing it to the shop. But it'd be nice to at least be able to tell them to either look into compression issues, or not waste their time and my money on checking for that. Plus I'll have the plugs out anyway, and I'm always interested in broadening my incredibly basic mechanical knowledge. Having said all that, I'm admittedly a novice, with a lot of dumb questions. I'm not stupid, I just have very little experience with all this, and I'm having to teach myself (or look to more knowledgeable guys like you) as I go.

                As far as the compression test goes, my dad went out and bought a remote starter switch in leu of the screwdriver method. It's a bit premature, since the oil/gear lube/plugs won't show up until next week, but that gives me time to get everything straight. So after looking at the starter in the motor, I can see two lugs coming off the bottom, both attached with nuts to cables.

                The picture isn't the clearest, but I'm pulling the rubber cover off the second lug.
                Dumb question number 1: Do I just need to connect the leads on the remote starter to these two lugs, and I'm good to go? Or do I attach the clip to some other part of the starter, along with the lug receiving power from the battery? Thanks for any clarification. Mine looks slightly different than this replacement one I found (just the fact that one lug points out to the side instead of both of them pointing down), but the only other thing I can see that I might clip to would be the wire that leads off to a separate connector, but I'm pretty sure that's something to do with ignition, which isn't something I want to mess with?


                Dumb question number 2: I know that a key component of the compression test is to keep fuel from getting to the cylinders (even I can figure out why that would be a bad idea). After looking at my motor, and the fuel line running into it, I don't see any obvious quick disconnects like you would see on smaller motors or ones with external tanks. Would removing the fuse that powers the fuel pump be sufficient to keep me from having any issues? I would plan on just yanking the two fuses (I'm not sure which one is for ignition and which one is for fuel, in the diagram they're on top and bottom, but in the fuse holder they're beside each other. I would think yanking the fuse for the ignition would further ensure I don't have any issues with that, anyway?)




                I realize I'm basically asking you guys to hold my hand through what to you is an incredibly basic procedure, and frankly I realize it's incredibly basic too. But just like someone learning to drive a stick shift for the first time or some other simple but non-intuitive task, I guess I just need to get the "For Idiots" explanation once, because I don't have any context in the situation. Thanks again for your time and help.

                Comment

                Working...
                X