Dropping a 2006 175 Optimax powerhead onto a 1995 175 carbed

[Fishinmymission]

So thank you very much for the picture. So that is how I think the early optimax before 2002 maybe we're routed for water coming from the thermostats. That is also how my old carbed motor was routed. The new optimax upper plates do not have the rear port drilled and tapped. They just have two fittings on the port side of the upper exhaust place for coolant with strainer which goes to fuel and air compressor on the side, and then bleed air from the fuel rail goes into the exhaust fitting. My manual shows up to 2001 and it is routed as you have shown.

I think newer optimaxes use those two plugged holes that you can see in the rear of your lower plate. I can tap one hole in my upper or 1 or two in my lower plate I think. If anyone else has pictures it could help.

[Fishinmymission]

Everything else is fine I have the 2001 manual and it all lines up except for this thermostat water. Both my newer ebay upper and original lower plates dont have tapped holes I need for thermostat dump water I need to decide if I tap the top orbottom plate.

[rock]

My info may have not been quite correct. Just noticed it was from a 2001 manual. Hope I didn't mess you up.

Rock

[Fishinmymission]

No worries I got confused looking at wrong part numbers on eBay. Finished tapping and hooking up the air coolant and gas lines. Since I had my old upper plate for reference I put the fitting in the upper plate again . Tomorrow I'll install the remote oil tank, the plastic airmanifold/alternator cover. I also pulled up the shift shaft when I pulled out the original engine so I have to drop the lower unit to align the shift shaft splines.

[rock]

You can line up the splines from the top with a little patience. Position it so it's in neutral and feel around with the shaft. Done it many times.

Rock

[Fishinmymission]

My prop is engaged to the driveshaft so I will try a bunch of different positions and rotations. This should save me some time I was going to drive to the boat ramp to take off the lower unit in the water. Did this once before to change a water pump without having to put the boat on the trailer.

[Fishinmymission]

Had I paid attention before I put the new power head on this would have worked unfortunately my shaft hits my powerhead and I still needed 3/4 of an inch to get onto the splines. Just finished dropping the lower unit in 55 degree water
Forgot my waiters so I'm freezing in wet sweats reading the oil priming sequence in my truck with the heat on. I will see if she runs shortly.

[Fishinmymission]

Can't keep it going at idle for more than 1 to 3 seconds without it coughing and stalling. Rpms are always pulsing and engine is kicking making me think some cylinder may not be firing giving an unbalanced shake. Advancing the throttle in neutral to around 1400 rpm is the only way to keep the engine running. Here's a video of it running with rpms pulsing between 1300 and 1600. I back a little bit off the throttle and it instantly stalls.

I talked with the seller he said it sat for a bit and it might be direct injectors he was willing to sell me 6 that came back from cleaning for $280. He also vouched for the compression test.
Ill hit each coil with the timing light to make sure I have spark tomorrow then Ill pull direct injector wires to try and Isolate the issue. Probably at least 2 not working for the engine to sound that bad.

I just had a thought. Pulsing in my engine is slow enough to count on video. I wonder what the compressor to crank rpm ratio is. I can easily count this by rotating by hand. If I see match to the pulse in the video I bet I have some sort of leak or issue with a regulator or tracker valve.

Let me know if you have any ideas.

My smartcraft resistor cap has been in transit from the neighboring town to my town for 6 days so it might be lost and I can't read engine codes till I have it.

[Fishinmymission]

So I have my diagnostic vessel view mobile ready to use and a guage with a schrader valve for diagnostics on Saturday. I'm almost certain I have an issue with either the tracker valve, air pressure regulator, or fuel pressure regulator causeign the surging and rough idle.

Also I finally found a picture from the merc parts catalog that confirms that the factory way for the 2006 is to route the water lines from the thermostats to the two holes in the lower exhaust plate with 883089 Fittings( I dont know what NPT they are). I did one tap in the upper plate and T'd my two thermostats together (the old way) because I was too lazy to tap two holes. This is how the water was routed on all the early DFI motors and I'm not certain why mercury changed it. If I feel like I get overheat in the cylinders or I burn up a prop seal I'll plug the upper plate and tap the two holes in the lower plate for better flow.

[Fishinmymission]

Both fuel and air pressures we're off my gauge over 120 psi. So I removed the likely culprit the air regulator and there was a torn filter and debris on the filter. I bought a new one but I tinkered with the old one. Not really sure how the debris could have clogged it as I can't see any small jets. It could have been just stuck. I removed the filter and freed the valve with all my strength and two Allen keys. Might try reinstalling the old one tonight.

[Fishinmymission]

So I messed up with the bleed air coming from the air rail regulator. The regulator was fine. The path into engine entered this pocket between my upper and lower plate with no outlet. You can see the silver lower exhaust plate represents the plate in my engine. I'm not sure how to solve this issue any advice is appreciated. The easiest way would be to take a small drill bit that fits inside the plug and drill the first wall allowing air to enter the exhaust and likely exit through the idle exhaust port. I'm wondering though if its possible for water to get back in that pocket when the engine turns off creating a freezing water risk. Another option would be to drill and tap where i have shown in yellow. Any thoughts?

[Fishinmymission]

I feel like it's bad etiquette to post on your own thread 6 times in a row but I had to conclude it. I disconnected the air rail hose from the exhaust plate and the engine runs smoothly at 550 RPM with no fluctuations. This is the best sounding easiest starting engine I have ever owned. Its all hooked up to my vessel view mobile and there are no codes relevant to my engine (i had to email vessel view about a few I wasn't sure of but they were not applicable). Also there is no fuel coming out from the compressed air hose. So I'm going to drill a hole in the parallel to water section of the lower cowling extend the hose and have it drain down there against the exterior of the exhaust housing and lower cowl (basically just like another water drain in the lower cowling). Just incase a diaphgram ever breaks it will spit fuel out of the engine instead of inside the cowling.

[Fishinmymission]

The engine ran amazing for the past 3 weekends with no issues (besides trying to put on a hub that was already spun on a spare prop that came with the boat). The engine performed top speed wise almost the same as my previous 175 HP motor. There might have been some small gains in hole shot.
With my vessel view mobile I was not happy with my fuel economy that I was getting with my old 14.5X19" prop, and according to calculators my boat was not getting the speed it was designed for. The prop was attributed to the crank and bearing failure so I was aware that I needed to pitch it down to raise my RPMS and not lug the engine. I was afraid I was going to loose even more top speed but this was not the case

The new 15X17" black max prop raised my RPMs by 350 to 5400 and I gained 6 mph top speed with another person in the boat, loaded with gear and fuel. My boat feels completely new to me and I absolutely love it. I just took it out of the water for the year after catching some blackfish but I can't wait to go fishing again in the spring.