Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Engine Repair
Forum Discription: Engine problems and solutions
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=37295 Printed Date: October-07-2024 at 2:27pm
Topic: RPMs - Engine issues or normal?Posted By: spiralhelix
Subject: RPMs - Engine issues or normal?
Date Posted: September-08-2015 at 3:57pm
So, I've always been pretty disappointed with my hole shot. The feeling while driving the boat was a "hesitation" before I could really feel the boat push the water. Well, on Sunday the conditions weren't the best, so a buddy and I decided to do some testing, and since I just had my 4-blade prop repaired, we figured we do some prop tests as well.
Back to the "hesitation", to try and eliminate carb issues, I had the carb rebuilt. Still had the hesitation, so I checked the accelerator pump as per all the instructions from previous threads. Hesitation persisted. One thing i really had never done before was keep my eyes on the gauges as i was more concerned about where I was going. So we affixed a camera to point right at the tach and speedo. In the below video, i cropped out the speedo as it doesn't really help with the tests and I generally use a GPS on the smartphone.
So my question is: Should the engine/boat/tach do what it shows with it almost jumping from in-gear rpms to almost 3k? There definitely was not a smooth transition through the 2-3k rpm range with either prop. It does look like the 4-blade recovers better.
https://www.youtube.com/watch?v=3oYNV1Gun5I" rel="nofollow - Camera View of the carb during hole shot . The link also shows both prop tests and a short cruising. In the linked vid, it appears that the carb is functioning correctly.
Suggestions? Our initial thought is maybe the fuel pump is starting to weaken and/or the fuel lines are starting to collapse from the ethanol. As Pete would say...test before throwing parts at it...how does one test the fuel pump (sinceince the carb is obviously getting the fuel.)..but not sure if it is the right pressure?
All thoughts are welcome!
Replies: Posted By: JoeinNY
Date Posted: September-08-2015 at 4:03pm
edit - What are the props in question? wait I see it now.. those props are not the latest and greatest tech - and they have been worked on. Consider a new Acme if you really care about a great holeshot
Posted By: Hollywood
Date Posted: September-08-2015 at 4:10pm
seems normal. that hesitation is possibly just before the hull planes out
Posted By: spiralhelix
Date Posted: September-08-2015 at 4:18pm
OK great. I understand the props are old. Glad to hear that is what is to be expected in regards to the RPMs.
Posted By: TRBenj
Date Posted: September-08-2015 at 4:26pm
400rpm difference between the 2 and both only give you 38mph? Put them both on the mantle.
Instantaneous prop slip when going WOT from idle is normal. The difference between the 2 where they "catch" is due to how much pitch they have, which is consistent with the wot rpm you see (and the differences between the 2).
This must be a '89 with those gauges and a 1.23? It really helps to remind us what boat and powertrain you have in order to generate meaningful feedback.
Posted By: spiralhelix
Date Posted: September-08-2015 at 7:10pm
Back at the end of July, the river was really calm and we were cruising at 37 mph (gps) at around 3600-3800 rpm (heading down stream). So Im thinking the rougher water didn't help top end speed.
As much as I would like to spend the $$ on a new prop, I have other life things eating up the extra cash. I'm not trying to barefoot or break any records, so having a boat that gets up to 35-36 is ok with me.