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175 Ocean Pro Hard start and low WOT rpm

R

redbird555

Member
Hi all,

Long time lurker first time poster here...anyway I have a set of 98 twin 175 ocean pros on my 251 mako. To my knowledge they have never been rebuilt or had the carbs done.

The boat sat for about 18 months prior to me getting it, the issue I am having is that the port motor seems to have a much harder time starting and does not reach the same rpm as the stbd. I can usually get the stbd motor to start after sitting for a few days with just the choke and a little throttle. The port motor always needs the ball pumped and then some finesse to get her to crank up. Once warmed up they both idle well and throttle up smoothly.

The issue I'm having besides the cold start is that the stbd motor seems much more responsive in the midrange (gains rpm very quickly with throttle input) and the port motor always needs more throttle to achieve the same rpm. At wot the stbd engine is at 5900 or so and the port is 5400.


I ran a compression test on the engines and the port engine with less rpm has compression from 100-112 on all cylinders and the stbd engine ranges from 105-120. So they both seem very healthy.


At this point I'm thinking it might be time for a carb rebuild but is there anything else I should check first?
 
I agree time to look at the carburetors.-------Use 12 kits and rebuild the 12 carburetors , and carefully look for warped carburetor bowls.----Does spark jump a gap of 7/16" on all leads ?-----Oil injection in service and tested ?---Or mixing at 50:1 on these ?
 
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racerone said:
I agree time to look at the carburetors.-------Use 12 kits and rebuild the 12 carburetors , and carefully look for warped carburetor bowls.----Does spark jump a gap of 7/16" on all leads ?-----Oil injection in service and tested ?---Or mixing at 50:1 on these ?
Click to expand...
VRO is in service and both engines consume roughly the same amount of oil so should be good there. I have not checked for a 7/16" gap but I have verified spark on all 6 cylinders.
Rwbutler said:
Same size props?
Do a full sync&link after carb job
Click to expand...

Yes same props, i was planning on doing a link and sync on everything when i got it all done. But to my knowledge in order to verify timing curves and such in that procedure you need a special omc tool no? I know the sync part on the carbs is done by hand and relatively easy
 
Check to see if the high speeds jets are loose on the port motor. This was a issue on these and drain screw swapped to a 344267. It has a tab that keep jets from backing out

crowley-344267--top__2_1.jpg
 
faztbullet said:
Check to see if the high speeds jets are loose on the port motor. This was a issue on these and drain screw swapped to a 344267. It has a tab that keep jets from backing out

crowley-344267--top__2_1.jpg
Click to expand...
Thanks man I think the carb kits come with new drain screws but I’ll be sure to look over everything. I can get Sierra kits local but I would have to order the omc kits. Any difference between the two I should be aware of? I use Sierra parts quite a bit and often find they have the same stampings
 
Thanks for the replies I pulled the carburetors off the port motor yesterday and found all 12 bowls were seeping fuel. They were pretty badly warped in addition to that it looks like someone has been in there before seeing as the intake manifold was missing one bolt on the right side and many bolts were loose on the left side

I haven’t looked at the starboard motor yet but I have 12 carb kits and 12 new bowls on the way. would the above mentioned problems caused the issues I was having on the port engine
 
Also the shop manual I have has the adjust for mixture on the carb body where the carbs I have have the screw on the metal intake plate and only the air bleed on the plastic carb body

since these things obviously had leaks I want to start tuning it from a base line. How many turns should I set them out to start with when they go back together?
 
When I went to the local evinrude shop one of the guys told me to inspect the carb flanges themselves where they bolt to the manifold for warpage....well lo and behold some of the carbs have warped flanges, cant get new ones either..

the guy had said they have had luck in the past with using a permatex form-a-gasket gasoline safe product with the oring seal to make up the difference. But im more scraed of it getting in the passages of the carb back there.. anyone have any input on this?
 
Got new carb bodies that were not warped and rebuilt those and swapped them on. It idles great now and drives pretty well. Weird thing is the port motor needed 10 turns on the screws to do this while the other one only was at 7 turns. The port wouldn’t even idle at the books 5 turns

however I still have the same issue on the port motor. I could only get 5200 out of it while the other was screaming at 57-5800 is there anything in the carbs that could cause this tuning wise? The high speed jets were all fine and clean when they went back in.
 
redbird555 said:
Got new carb bodies that were not warped and rebuilt those and swapped them on. It idles great now and drives pretty well. Weird thing is the port motor needed 10 turns on the screws to do this while the other one only was at 7 turns. The port wouldn’t even idle at the books 5 turns

however I still have the same issue on the port motor. I could only get 5200 out of it while the other was screaming at 57-5800 is there anything in the carbs that could cause this tuning wise? The high speed jets were all fine and clean when they went back in.
Click to expand...
Did you do a synk&link
If you did both motors are timed the same?yes?no?
 
redbird555 said:
I did not. I had the easy timer and verified timing that way but was thinking of using the timing light to verify consistent spark
Click to expand...

Another thing I want to note is that in the mornings the port motor (with the issue) always needs the ball pumped before it will start the stbd engine i very rarely have to pump the ball at all and she fires right up. Both fuel balls are new, could i have a fuel pump issue in the vro? Thing is that it oesnt surge at high rpm its just like past a certain throttle input point it stops gaining rpm where the other one jumps right up to 5700.

I have the service manual and will be checking the powerpack and rectifier, along with the coils. Is there any place you all would start first including the vro?
 
redbird555 said:
Literally just read about it yesterday on here so I’ll try it today or tomorrow. Does it need to be under load
Click to expand...


redbird555 said:
Literally just read about it yesterday on here so I’ll try it today or tomorrow. Does it need to be under load
Click to expand...

bringing this back to the top. Winter project in the boat kept me from really using much but now I’m digging back into it. I’ve attached a video of both engines. The boat is in nuetral and I just use 1 engine at a time to try and get it up on plane. It’s pretty clear on the one side that one engine will get it up on plane no issues. Then with the other side I pin the throttle and it doesn’t go anywhere really and the rpms just stagnate.

all 12 carbs were rebuilt at the same time, if I push in the choke at high rpm the rpms fall like they should. So far I have changed the following.

1. new OMC power pack
2. new CDI voltage regulator/rectifier
3. New wires and 3 new Sierra coils
4. new CDI optical eye sensor
5. Verified spark on all cylinders at idle on muffs

im really stumped, I suppose it could be the that one of the CDI parts is a dud or maybe the stator and I’m not against changing the stator but would that cause the symptoms I’m experiencing?

sorry one video had to be cut short because of boat traffic but you get the idea. Check the linkages once again and both sets of throttles reach wot with the blades all the way open and max out the timing slider


First video of engine that runs fine other side in nuetral:
https://youtube.com/shorts/gQnbEwzmtTI?feature=share

second video other engine in nuetral this one with no power:
https://youtube.com/shorts/9ydJ6JE6-ig?feature=share
 
Also I realized I made a mistake when writing the original post. For some reason I kept saying port when stbd is the one with the issue lol sorry about the confusion
 
Is there spark on all 6 leads , yes or no.----Good spark that will jump a gap of 3/8" or more ?-----Checked the shift interrupt switch ?-----Switch is found near shift linkages on the motor.----Stops spark on 3 cylinders momentarily during shifting.
 
Push in and hold choke on low engine..if it picks up fuel delivery problem. Check sync and link as sound like carbs/timing not fully open
 
racerone said:
Is there spark on all 6 leads , yes or no.----Good spark that will jump a gap of 3/8" or more ?-----Checked the shift interrupt switch ?-----Switch is found near shift linkages on the motor.----Stops spark on 3 cylinders momentarily during shifting.
Click to expand...

I used a spark plug inline light and verified all 6 cylinders are firing at idle

faztbullet said:
Push in and hold choke on low engine..if it picks up fuel delivery problem. Check sync and link as sound like carbs/timing not fully open
Click to expand...
I have done a link and sync many times all the carbs open fully also when at 4000 rpms at c try use I pushed the choke in and the engine bogs down just like it should
 
Well I was messing around to with the linkage today just to triple check myself. Everything is opening as it should however I noticed that at about 3/4 throttle the timing arm maxes out on top of the flywheel. After that the last bit before WOT is all on the carb linkage. This is the same in both engines

however that is precisely the point where I stop gaining rpm. So in other words when the timing Maxs out I don’t gain any more rpm with throttle but on the other engine the rpms keep climbing. What controls the timing advance? Why would it stop gaining rpm at that point
 
On most outboards the timing goes fully advance BEFORE throttle plates go fully open.----Are all the wires from the powerpack going to the correct coil ??----This lack of performance should be easy to figure out in my opinion.
 
Yes you’re right the timing Max’s out before the carb plates are fully open on both engines. What I meant to say is that when the timing maxs out on the stbd engine is when it stops gaining rpm. The last bit of throttle doesn’t result in more rpm unlike the port side which will keep gaining
 
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