Engine Rebuild |
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craigslisthooker
Newbie Joined: September-18-2014 Location: San Diego Status: Offline Points: 18 |
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OOOOk. So, I had a guy come out to check the timing. We took and out and he was convinced that the timing is on because we can get consistent repeatable backfiring. We are experiencing-> 3500 rpm for 1-2 minutes and we start to lose power. RPM's slowly drop by 200, then bang bang.
We investigated the carb and made some adjustments. We took it back out and the backfiring shifted. So now, we can take it 4000 RPM for 1-2 minutes and when backing down, we get a lean pop from the carb. After another 1.5 hours of carb adjustments, same issue. Next step-> Sounds like a fuel issue, so let's replace the fuel pump and make some more carb adjustments. We take it back out and it's now running a little rough at idle. Also, 3600 RPM and full load, we still get the slow loss of power and pops, but this time after a little longer on the run. This last weekend, we took it out and I can hear a little surging and a little loss when cruising around 3300 with full load. I wonder if this is normal? I'm going to replace the entire fuel line this week and remove the old scanflo fuel consumption sensor and see if there is some sort of fuel restriction going on. Lastly, I did discover the "NEW" Carb that was installed 7 months ago is probably not new. One of the gaskets deteriorated when we made an adjustment. I'm gonna chase down the clowns that sold it to me. If anything sticks out to you all or if you have any recommendations, I'm all ears. |
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dan-ger
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63 Skier
Grand Poobah Joined: October-06-2006 Location: Concord, NH Status: Offline Points: 4269 |
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I don't know what he meant by this, but here's my comment. The timing is either correct, and advancing correctly to the correct total advanced timing, or it's not. He can't be "convinced" because of some other thing that is happening, the timing light says the timing is right or it's wrong. So having said that, I thought your advance mechanism might not be functioning correctly. I still think that's possible, but that loss of power over time sounds like a different issue. Lack of fuel for sure could cause it, but if it was me I'd still prove out the ignition first. Has the coil been changed? You're spending a lot of time on the carb but if the carb is bringing it up to 4000 rpm and running fine, the carb likely isn't causing the power loss problem a few minutes later. |
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'63 American Skier - '98 Sport Nautique
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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Dan, What was the advance on the timing? The advance has been mentioned several times. What carb adjustments were done? |
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craigslisthooker
Newbie Joined: September-18-2014 Location: San Diego Status: Offline Points: 18 |
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Sorry I wasn't clear. When i say we're convinced the timing is on, I mean that we ended up not putting the light on it because it looks like we are chasing a fuel issue, not a timing issue. This was concluded because it sounds great at all RPM's until the power starts drifting, then we get the lean popping. The carb adjustments on the primary and secondary pushed the backfiring around on the RPM spectrum, so we tried to dial it in. It still feels like it's starving for fuel when the backfiring is about to occur.
I have only had the boat for 8 months and the coil hasn't been changed under my watch. I suppose a new coil is quick and relatively cheap to narrow down the issue and it certainly wouldn't hurt to put the timing light on it. I will run through the fuel line, coil, timing, and then check back in. |
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dan-ger
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TRBenj
Grand Poobah Joined: June-29-2005 Location: NWCT Status: Offline Points: 21169 |
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Start by checking the timing, like we said.
Ignition problems (especially timing) should always be ruled out before moving on to fuel- especially when he symptoms point to an ignition problem. The symptoms you describe are not consistent with a fuel delivery problem. |
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phatsat67
Grand Poobah Joined: March-13-2006 Location: Indiana Status: Offline Points: 6151 |
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Like Tim said, it is a pretty basic simple system test it all and you'll find your issue. Much better to KNOW something is right rather than ASSUME it is.
Proper run down of an ignition system shouldn't take you long. Do it and know it's right then move to fuel. |
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craigslisthooker
Newbie Joined: September-18-2014 Location: San Diego Status: Offline Points: 18 |
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Message received!
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dan-ger
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63 Skier
Grand Poobah Joined: October-06-2006 Location: Concord, NH Status: Offline Points: 4269 |
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Dan, do you have any pictures you could post of the boat? Would be nice to see the Fish!
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'63 American Skier - '98 Sport Nautique
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craigslisthooker
Newbie Joined: September-18-2014 Location: San Diego Status: Offline Points: 18 |
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All I can say is, you all are the best. And, timing is everything. I pulled the old fuel floscan out of the fuel line, set the timing, and away we went. She sounds great. No issues at all.
Thank you all for your comments and help!! |
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dan-ger
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jgold
Newbie Joined: August-04-2013 Location: United States Status: Offline Points: 19 |
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I have been viewing this site for a long time but never posted anything. I was reading everyone's posts trying to get some information on my own rebuild. But I haven't found the information I am in need of and was wondering if one of you could help me? I have ordered all the parts to rebuild my 351W in my 1983 Nautique. I was told what parts i needed for the reverse rotation motor by SKIDIM. However I am having trouble finding the rear main seal. Mine is a 2 piece and SKIDIM told me that I needed a Felpro 17748 gasket set. In my search I have found that this gasket has been discontinued. Do ya'll know if there is another company that offers a reverse rotation specific 2 piece gasket set for the 351W?
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TRBenj
Grand Poobah Joined: June-29-2005 Location: NWCT Status: Offline Points: 21169 |
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You can use a bidirectional seal on the 2-piece seal style blocks. The reverse rotation specific wick lines are machined in the crank. Only the newer (1-piece) blocks require rotation specific seals, as the associated cranks are smooth.
Search for the rebuild thread that Alan (81nautique) put together on his rebuild- it'll tell you all you need to know. |
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jgold
Newbie Joined: August-04-2013 Location: United States Status: Offline Points: 19 |
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Thank you. I will read that thread.
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jgold
Newbie Joined: August-04-2013 Location: United States Status: Offline Points: 19 |
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I finished with my rebuild. What I believe to be true about the rear main seal is that as long as it does not have the gnarls it will not leak. Mine is doing fine. However my engine is running hot at idle speeds. It did this back in 2010 and I bought a new raw water pump from SKIDIM and that fixed it. I just replaced the impeller. I am having a hard time believing that the pump is bad already. Do you think that the water pump on the block could be the culprit?
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jgold
Newbie Joined: August-04-2013 Location: United States Status: Offline Points: 19 |
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I finished with my rebuild. What I believe to be true about the rear main seal is that as long as it does not have the gnarls it will not leak. Mine is doing fine. However my engine is running hot at idle speeds. It did this back in 2010 and I bought a new raw water pump from SKIDIM and that fixed it. I just replaced the impeller. I am having a hard time believing that the pump is bad already. Do you think that the water pump on the block could be the culprit?
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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No, I don't feel it's the circ pump. What do you consider hot? Check for air leaks on the suction side of the RWP. |
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craigslisthooker
Newbie Joined: September-18-2014 Location: San Diego Status: Offline Points: 18 |
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Did you replace the thermostat when you did the rebuild? If so, did you replace it with the correct specs? Also, how old is your water pump? Did you do a major rebuild or a just the impeller? Corrosion can build up over time in the bearings and slow your pump. Lastly, you may want to check the risers, intake/ exhaust and manifolds if the easier checks are OK. There's not much else in the cooling system.
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dan-ger
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jgold
Newbie Joined: August-04-2013 Location: United States Status: Offline Points: 19 |
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I didn't let the engine go over 200°.
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jgold
Newbie Joined: August-04-2013 Location: United States Status: Offline Points: 19 |
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(Did you replace the thermostat when you did the rebuild? If so, did you replace it with the correct specs? Also, how old is your water pump? Did you do a major rebuild or a just the impeller? Corrosion can build up over time in the bearings and slow your pump. Lastly, you may want to check the risers, intake/ exhaust and manifolds if the easier checks are OK. There's not much else in the cooling system.)
I did not replace the thermostat. However it cools down when running faster than idle. So I would think that would rule out the thermostat. I only replaced the impeller on the raw water pump. |
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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This is an indication of an air leak on the suction side of the RWP as I mentioned. |
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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Dan, Could you explain the corrosion in bearings slowing the pump? |
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craigslisthooker
Newbie Joined: September-18-2014 Location: San Diego Status: Offline Points: 18 |
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Smooth, clean bearings = smooth bearing and pump performance, dirty bearings = poor bearing performance and hence, poor pump performance. Bearings used in harsh conditions (water) are more susceptible to wear. Don't hold me to the exact times, but the manual states impellers should be replaced every 2 years, and major rebuilds/new pump should be every 4.
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dan-ger
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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I'm confused! You stated "slow your pump". Wouldn't that prematurely wear belts? How does a bearing perform poorly? "Harsh conditions" does that mean you consider a boat to be worse that a car out in the rain and salted roads? |
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craigslisthooker
Newbie Joined: September-18-2014 Location: San Diego Status: Offline Points: 18 |
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Have a great day.
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dan-ger
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jgold
Newbie Joined: August-04-2013 Location: United States Status: Offline Points: 19 |
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I pulled the hoses from the lake pick up to the raw water pump off and I believe that hoses from the lake pick up to the strainer and the hose from the strainer to the transmission cooler both need to be replaced. I will keep ya’ll updated
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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James,
When you replace the hoses, it's recommended to use wire reinforced on the suction side of the RWP. |
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jgold
Newbie Joined: August-04-2013 Location: United States Status: Offline Points: 19 |
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I got the hose and installed it. That helped but I still had a problem. So I installed a new thermostat and put RTV sealant around the strainer gasket. This solved the problem. I really believe that the strainer was the culprit. I am now thinking that I may replace the new 160° thermostat with a 143° one. The boat is running about 190° now. It always ran about 170° before.
Thanks ya'll for the help. |
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gun-driver
Grand Poobah Joined: July-18-2008 Location: Pittsburgh, Pa Status: Offline Points: 4127 |
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Yes put the 143 back in. Glad you found the air leak
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MrMcD
Grand Poobah Joined: January-28-2014 Location: Folsom, CA Status: Offline Points: 3735 |
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your boat should always run right at the thermostat temp when warm. If you are running hotter than your thermostat temp you have an issue with flow that needs to be fixed. The only time my temp creeps up is when something is going bad. I would keep checking for a air leak on the intake side or a blockage on the thermostat side. Many times when a impeller goes bad you will find parts of the bad impeller blocking the flow upstream. They have to be removed to get full flow again.
Normally an air leak or a worn impeller will let you run hot at idle but cool down running, either way fix it then enjoy your boating season. |
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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Mark, I question the above statement. It has been documented many times here that a hard run will get the temp over the T stat rating. |
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jgold
Newbie Joined: August-04-2013 Location: United States Status: Offline Points: 19 |
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I also question Mark's statement. It just makes sense to me that the motor would be warmer than the thermostat because the thermostat is away from the motor on an inboard engine??? Right where the raw water comes into the little block that is mounted onto the engine's block.
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