Help Repowering Boat

[HookedOnMarsh]

Hello. I'm looking for any input about replacing my old 86 175Blackmax on my cuddy cabin. I'm looking for a used motor in the 150-200hp range.

If I stay with Mercury, will all my controls and gauges work with say a 2000 year model or newer?

Any of the EFI or DFI motors I should avoid?

What kind of gas mileage increase will I get with these newer motors? And which would be better 150 or 200hp on gas mileage and performance?
This boat will be used to go offshore with a full load of 60 gallons fuel, ice chests, and kids.
Thanks for any advice.

[reelapeelin]

Hello. I'm looking for any input about replacing my old 86 175Blackmax on my cuddy cabin. I'm looking for a used motor in the 150-200hp range.

If I stay with Mercury, will all my controls and gauges work with say a 2000 year model or newer?

Any of the EFI or DFI motors I should avoid?

What kind of gas mileage increase will I get with these newer motors? And which would be better 150 or 200hp on gas mileage and performance?
This boat will be used to go offshore with a full load of 60 gallons fuel, ice chests, and kids.
Thanks for any advice.


150 is plenty to get you and the load you describe offshore...if the controls will work (somebody hopefully will answer this), I'd say find a good Optimax 150...go as new as you can and check it out good...they are about as fuel efficient 2-stroke outboards as they get...if your existing controls won't match up to newer motor, then you're open to lots of options...late-model FICHT, Opti, and other Direct Injections...a 140 Suzuki 4-stroke will work well and be a REEL fuel-sipper...

[THEFERMANATOR]

The controls and steering should hook up to the newer engines, but the harness's changed somewhere in the late 90's when they started offering SMARTCRAFT. You can buy adapters I believe to make it work though. As far as going with an OPTIMAX, I wouldn't unless it's new or still under LOTS of warranty. At the very least don't buy one older than 03 as that is about the time they got most of the bugs worked out. The 150's weren't horrible, but there was a reason they earned the nickname OPTIPOP's. The 04+ have been pretty solid though with the only real issues being belt failures for the air pump that leave you dead in the water, but that is more of a amaintence issue than anything else. As for FICHTS I would stay 03 and newer as well. Persoanlly I like the older engines as I can buy ALOT of gas and parts for what the cost of a new engine is.

[HookedOnMarsh]

Thanks for the info guys. That is what is what I was guessing too. I'm not a big fan of all this extra electronics and stuff in a marine environment. So that leaves me another option. Would I be doing wrong if I just got a new complete powerhead for around $2500? The one I found is a 200HP 1988 Blackmax complete with everything, just drop on and go. Has new rings and bearings and has been dynotested for a 4 hour runtime. My lower unit seems strong now, no noises or vibration. It should be able to handle the 25 extra horses. What you guys think?

[reelapeelin]

I think a rebuilt powerhead would be a good choice as long as you have a LOT of confidence in the shop that built it and the automatic oiling system has been either disconnected or THOROUGHLY checked out, rebuilt, cleaned and tested...particularly that little nylon gear that has a history of failure in those motors...it'd be a shame to pay for a newly rebuilt powerhead only to have the auto-oiler blow it for ya...clean out the oil tank and the pick-up tube, too...

[spareparts]

whats wrong with the powerhead you have now?

[bigshrimpin]

whats wrong with the powerhead you have now?

If it ain't broke? . . . You know!! The motor you have is a great engine!!!

Here are a few things to consider.

1. you'll be lucky to get the old powerhead off the mid-section.

2. There's not too much power difference b/w a 175 (vertical reed 2.4L) and a 200 (horizontal reed 2.4L) . . . 175 and 200 use the same block with a different front half, exhaust tuner and carbs. an 88 200 might have the 1pc. heads, but it's still essentially the same engine as the 175.

3. Fuel economy is worse (although not bad) with the 2.4L 200 depending on which carbs wh-31's, wh-28's, wh - 22's, wh-20, but all the larger verturi carbs are worse on fuel than the small venturi carbs on the 2.4L 175.

4. 1992 and later 200's used the 2.5L block which has behind the liner porting. 2.5L merc's are STRONG motors, but they like fuel a LOT more than the 2.4L motors.


Ask MJ about his fuel economy with a 2.4L 175hp (2:1 ratio lower) pushing his 23 SeaOx with a hardtop.

I run a 1979 2.4L 200hp vertical reed (essentially the same motor as the 175 (without fingerports) ) and I get 3.5 mpg up to 4200rpm almost all conditions pushing my 20 seacraft seafari.

[HookedOnMarsh]

Well the reason I'm getting rid of this powerhead is I can't figure out exactly what is wrong with her, but I think the exhaust plate or bottom crankshaft seal is leaking water in the #5 cylinder. It is only a little amount of water; shows up on the plug as a water droplet after shutting down the engine on the garden hose. Cylinder is not cleaned out looking and the plug otherwise looks normal except the small water droplets on it. My block has seen so much saltwater that the thought of turning any bolts on it is a nightmare, and we know how many bolts go around the exhaust cover. I dread just pulling the powerhead off after what I went through with the removing of the lower unit and the right cylinder head.

I still have around 100psi compression, all even within a couple psi. The stator low speed windings burnt out due to a bad idle/advance module. I have replaced the stator and removed the module. Only electronics on it now is the switchboxes and the rectifier. I have advanced the WOT timing up from factory 19 to 24 at WOT to compensate for the missing advance module. I am only getting 5200-5400RPM out of it and is hard to start sometimes. If you hit the gas after startup it just sputters and then clears out and runs. Now it likes for you to ease it up on plane and then WOT. When it's running high speed it never misses a beat. Startup idle is horrible and smokes out the place sometimes and sometimes not so bad. I'm going to try removing the oil injection and premixing somewhere between 50:1 and 75:1 and see if the smoking at idle goes away.

Another thing I notice is once I get it moving everything seems fine and takes off fine. Just seems very cold natured acting until its ready. Could all this be because I don't have that idle/advance module? I hate to throw another powerhead on it and it do the same thing all because this little black box went bad and it can't adjust the timing as needed to keep the motor running in gear after starting it? I understand you can't even get these black boxes anymore because they failed so often? Where could I possibly get a good one? I don't care so much that I lost the few degrees advance but the low speed idle advance would really help out my problem.

But in the long run, I think I would be best served getting rid of this block and getting something else. I want a motor that can get this boat out to the blue water and back without problems. 50 miles out is not uncommon. My friends say they would feel very safe in my rig that far out, but not with that motor. My buddy, CB on the last trip out was talking and petting the 'sweet girl' when she didn't want to start the last time. Really was funny to watch him do that, but rather not have to see us do that again.

[macojoe]

I have the 1985 175 hp that BS speaks of, Its on my 23' Sea Ox and it gets up and goes awesome!! I get 2 1/2 to 3 miles a gallon and this boat is one heavy ba2tard!!
I have always hayed Merc's but this one is great!!

[HookedOnMarsh]

I guess it's just my luck that this happened to me. Motor ran great when I first got it and man it had unbelievable power. It would launch that big tub and would have to pull the throttle back just a hair to keep from going over 6000RPM. Now full throttle and only 5200-5400. My top speed has also dropped from low 40's to around 35MPH. Was nice while it lasted though!