Slow hole-shot acceleration

[dmwerwie]

Last year I bought a used 1986 Checkmate ski boat with an '86 Evinrude 140hp V-4- both in extremely good condition. The engine was modified over 10 years ago to run on less than 90 octane. The boat was used for skiing and tubing by the previous owner and has a 3-blade stainless prop. Ever since I've owned the boat, I've had a hard time getting skiers popped out of the water. Often when I pump the fuel bulb before cold starting, the bulb does not get hard despite a lot of squeezes. There is no problem starting or with top speed. Earlier this season, I noticed the hose connection to the fuel bulb wasn't a perfect seal. It seemed to be letting air in or out when I squeezed the ball. One side of the hose connection into the bulb is wrapped with a lot of electrical-type tape. The other side where I noticed the air isn't wrapped. I was able to push the hose more into the bulb connection, but I'm wondering if there was a better seal if I'd get better acceleration from a dead start. If not, any other ideas?

 

[wdknox]

Re: Slow hole-shot acceleration

DMW,<br /> When your boat is at idle or when you accelerate does the engine run smoothe. If it does you may just need to repitch your prop. The amout of weight in the boat and the fact that you are pulling skiers can put a lot of load on an engine. In some cases the only way to compensate for this is to lower the pitch of the prop. I know with one of the boats I have had in the past I had a prop for joy riding and another for skiing, the lower pitch prop stayed on my boat most of the time. And the distribution of weight in your boat can make a big difference, moving as much weight forward as possible can help to get a boat up from a dead start. As for the bulb, I would replace because it sound like it might be bad. I don't think that would be your problem but I could be wrong. Anyway good luck and I hope some of this might help.

 

[DJ]

Re: Slow hole-shot acceleration

DMW,<br /><br />Tape on a fuel hose is NOT a good sign-replace the assembly.<br /><br />Follow ^Texasboater's advice. Your top RPM should be somewhere aroung 5800.

 

[Spidybot]

Re: Slow hole-shot acceleration

I agree with both.<br /><br />When you're at it, also check for mount hight, trim angle, hull condition and prop damage.<br /><br />4-blades normally performs well when skiing and have less slip. Even if you are within specified WOT range, you may need a lower pitch to improve accelleration.<br /><br />If you want to know more about boats and props, go to this page

 

[dmwerwie]

Re: Slow hole-shot acceleration

In response to texasboater, my engine does idle well. However, the throttle isn't responsive. If I push the throttle forward, there is little to no acceleration. I have to go almost 1/3-1/2 throttle before I notice any power gain. I can then back off a little once underway. I do notice that at 1/3-1/2 throttle, the engine runs rough. I don't know the proper terminology to describe it. It seems choppy or jerky. Is that porpusing? I appreciate all responses. Any follow-ups to this will be much appreciated as well.

 

[JB]

Re: Slow hole-shot acceleration

Howdy, DMW.<br /><br />"Modified to run on less than 90 octane" may be a clue to your troubles. Your engine was built to run on 87 octane unleaded fuel.<br /><br />The "modification" was probably ignition timing retard. That would delay full advance of your spark timing until almost wide open and greatly reduce your mid-range torque.<br /><br />Before you start spending bux on props, do a detailed "link 'n'synch" on the carbs and the link to the ignition timing plate.<br /><br />Let us know what happens.

 

[dmwerwie]

Re: Slow hole-shot acceleration

JB,<br />The engine's manual says that 90 octane is recommended but devices can be installed so that the engine will run on lower octanes or lead-free gas. That is the device that was installed.

 

[Dhadley]

Re: Slow hole-shot acceleration

Back in the mid 80's OMC did recommend high octane because they believed it had more "cleaners" than 87 or 89. I never did see that in writing but that's what we were told at the service seminars. If I remember correctly, they were refering to cross flows (hence ths "fat" head gaskets, jet changes and/or retarded timing) but the loopers (like your 86 140) were expected to run on 87 with no mods.<br /><br />I would agree with JB and check the timing and sync and link carefully.<br /><br />Good luck!

 

[dmwerwie]

Re: Slow hole-shot acceleration

My mechanical ability is pretty limited. Can someone recommend how to go about timing, linking, syncing, etc.? Thanks.

 

[Dhadley]

Re: Slow hole-shot acceleration

The service manual has an excellent discription. Including some VERY helpful pics. It will be your "shop bible".<br /><br />Let us know how you make out!