Engine Rebuild

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.

craigslisthooker wrote: OOOOk. So, I had a guy come out to check the timing. We investigated the carb and made some adjustments.

Dan,
What was the advance on the timing? The advance has been mentioned several times. What carb adjustments were done?

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.

Message received!

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!!

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.

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?

jgold wrote: 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?

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.

I didn't let the engine go over 200°.

jgold wrote: 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.

This is an indication of an air leak on the suction side of the RWP as I mentioned.

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.

Have a great day.

James,
When you replace the hoses, it's recommended to use wire reinforced on the suction side of the RWP.

Yes put the 143 back in. Glad you found the air leak

MrMcD wrote: 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.

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.