Help - 4.3l Engine sputters/stalls out above 2500 rpm

buick6472

Cadet
Joined
Aug 6, 2010
Messages
10
First of all, I must applaude this forum and its veteran members that spend so much time helping others. This is a great site. I have learned alot in the last week.

I just purchased a 1996 Four Winns horizon 170 with a 4.3L Volvo engine. It was running great but on the 2nd time out on the water (about 3 hours running time combined since i got it) it started sputtering at almost WOT. I think it was around 2500-3500 rpm. It did this almost every time i tried to get on plane. And sometimes actually got up on plane and ran fine for a minute or so then the same thing again. Then it started stalling after the sputtering i just described. And would only start (was turning over) after a few minutes of rest. After finally starting it would run fine at or just above idle. Which is how i ran it for about another hour until pulling the boat out. I run the blower only before and when warming up the engine at the boat dock. Not sure if that has anything to do with it. Should i run it all the time? Or when going slow? Before buying the boat, on the test drive we had to put some fuel in it due to a faulty sending unit (which i replaced already) but we thought it was empty so $10 of gas actually filled it up as i later found out when changing the sending unit. So I don't know how old the gas is that was already in it but it was nearly full. So, after the episode at the lake i got home and pulled the sending unit again and looked closely inside at the bottom of the tank and saw a few small particles here and there but nothing i thought would cause a problem. I looked for water but really couldn't tell. Not sure if the water would be obvious on the bottom of the tank or not. I inspected the cap and rotor which both were in bad shape. I don't think that they had ever been changed because the only marks on the screws were by me from removing them. The screws had some kind of coating on them like maybe paint from the factory. By the way, can i just get a cap and rotor from an auto parts store or are these parts specially made for marine use? I have learned of the fuel/water seperator filter and will change that also. What other things should i be looking for? Electric fuel pump not able to deliver volume for higher speeds maybe? I have checked all electrical connections. I didn't see an anti-siphon fitting on the fuel line by the tank. Would it be somewhere else downstream? Or are anti-siphons only for applications where the fuel line is lower than the tank itself? Are there any sensors on these engines that could cause this problem. I have good steady oil pressure also. Sorry for such a long post i just wanted to capture everything i could to make it easier.
Here's the info on Boat/engine:
1996 Four Winns Horizon 170
4.3L Volvo Penta
Model # 432APHUB
Serial # T01286369
 

whitney

Seaman
Joined
Jul 26, 2010
Messages
69
Re: Help - 4.3l Engine sputters/stalls out above 2500 rpm

I'm a newbie too but I'm learning rapidly, and I have a similar engine --

Read the FAQ ("Adults Only") section 13 on WOT and take the time to follow all of the tests ... especially about fuel pickup issues. It will take some time but will be well worth it in knowledge gained, and I bet you will find your problem.
http://forums.iboats.com/showthread.php?t=288430

Sounds like trash in the tank issue to me. Pump is probably fine, I haven't heard of many pumps that partially work. You definitely should replace the filter, and should check the inlet screen on the carb.

Blower shouldn't matter, and I wouldn't worry about the cap and ignition system until you have looked into fuel. Best thing I did when chasing my WOT issues was to do most of the tests in #13 to rule out my fuel system (now I'm finding problems in the carb).
 
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