I have a 1995 V180 procraft fish & ski with a 1995 Mariner Mag III 150 HP.I have replaced the tach and switched the gray wire from one regulator to the other and the tach did't work at all then so switched it back and adjusted switch on back of tach it works sometimes.Now to the next problem took it out for a run and stopped to fish a while about 3 hrs it had ran fine till I stopped to fish.When I took off it came about half way out of hole stayed there about 200-300 yds then went to full throttle and ran fine.The next weekend took it out and ran shore line about a mile or so just off idle and did't notice anything wrong till it sounded like it picked up a cyclender or two hit the throttle just got on plane at about 3000 rpms and tach working at this point??? and never came out of it.Put on trailer and ran compression test 135-145 psi on all 6 and have spark on all 6 does anyone have any ideas what I need to check or do next NEED HELP Thanks

I lost my tach on my 96 merc, also had power issues.. found out my voltage regulators were burned up. Boat ran fine until my battery's started getting low thats when I had started having HP issues. replaced them and boat runs like a champ.

Ok thanks I think need to check stator & trigger assy. as well as regulators I have been told to clean carbs as well does anybody know if these things can be checked at home myself I have been a auto & truck mechanic 35 plus years and Iknow that marine is different but a lot the same. Or is it best to have a shop check it because of the price of the marine parts

First thing to do is the easy, least expensive: carb cleaning, fuel lines, fuel filters, manual fuel pump diaphragms, spark plugs, inspect ignition wires, test on a remote fuel tank with fresh fuel. I don't see you having a problem working on the motor but it is always advisable to have a service manual for that motor.

I do think I need a shop manual for the motor and with auto electrical always start with the easy stuff first Because some times I can't see the forest for the trees lol. and it is a very nice boat just put all new seats and carpet graph and new troll-motor the out side of boat is in great condition so I will be keeping it for a while do you know where is a good place to get a manual? and thanks for the help

Get a manual. It will tell you how to test stator, trigger, and switch boxes. If you have fire on all 6 at low speed but not higher rpms then is probably the stator.

I think your compression gauge is wrong. I have never seen 135-145 on any motor not
even a 12 to 1 race motor. I would think the compression should be more around
105-110. Maybe you have a large carbon buildup.

Johnny

I would agree on a stock motor. My Merc with milled heads was 135+ after rebuild and break in. It was a little higher in its early years right after milling the heads.

Norm should be 115 and up ona healthy, never opened, older motor. Could have cut heads, decked block, 31/34 cc heads or any combination of.....or could be gauge also. Just another reason for 2 gauges if one isn't "known" ta be accurate...

What Gary says is always a good thing especially ona older motor if you don't know its history. Stator and regs are pretty suspect as well. If it still has idle/timing stabilizer on it it needs go in tha trash. Idle and max timng will need ta be reset. Needs ta be done (at least checked anyway) if comp number is correct.....jmo

I have checked compression again with a different tester and found it at 130 to 140 on that gauge. have not pulled heads but to look in plug holes the top of pistons show very little carbon most of piston is clean I have ran sea-foam in it most of summer. It still has idle stablizer on it is there any wiring changes need done to remove it or just unplug it and reset low-high timing also the fuel that came out of carbs was clean and clear pulled carbs and cleaned them and no change. The motor shows no signs of ever been opened up and fuel pump has been done at some point no paint on rubber diaphrams but don't know when it was done. I need to check regulators and stator I have a DVA. but it is a GM tool from the 80's of of a recall on Vet's ignition system not sure to use it or not they are on Ebay for $50.00 I will order it and manual to check them both I think there is a regulator/stator problem when I changed the tachometer there was a burnt place around the sender post on tach thanks for comments I do need the help also checked charging at fast idle not charging at all showed 11.3 volts

Goggle this "V6 Outboard EFI". Look for this "Outboard V6 EFI - RIVER-SERVICE.RU". Will be a pdf. Its oem for efi but ign. and chargin' will be tha same. It might work for ya till ya get your "OEM" MANUAL. Don't bother with any other type manual.........Not familiar with your dva.

jan. Its really a [censored]-shoot ta diagnose a problem ona computer.......gl

You can just disconnect tha module or remove it completely. Just make sure a "jumper" remains in place between tha biais post on tha switch boxes (white/black tracer).

Setting tha timing. After TDC and pointer is verified (manual)
1. Butterflies closed on all three carbs.
2. Slight gap between throttle cam an linkage roller.
3. Use idle timing screw only. No linkage adjustments for idle speed. On tha hose set at 800 ta 1000. Set real rpm in tha water, in gear (on tha trailer is ok) ta whatever makes you and tha motor happy.

Max.......
Hot battery, cranking speed, timin arm against stop on tha block. Set at 23* advance.

Ok thanks I will be back at lake this weekend and will have time to be in shop because they are calling for 5.5 in of rain so I will play with it Thanks for the help

I had a similar issue on a Yamaha, ended up being the rectifier. $75 for a used one on EBay and she runs good as new. Tach was acting funny as well as the tilt and trim. Lost top end power.