Mariner 150hp advise.

[POINTER94]

I have a 1986 Mariner with oil injection and I have actually had a lot of good luck with it. Two things: She blows alot of smoke at low RPM, and I just feel like a 150hp should be able to turn better than 5200rpms safely. <br /><br />I have this mounted on a 17ft Larson and it has been very good overall except for the smoke and a rough idle. My mechanic put it this way "You bought a racehorse, run it as such." Well thats nice but that isn't exactly what I expect. I am thinking of using the synth, oil for the injection system. Will this help. I have seen a lot of people disconnect and direct mix, but I am leary of doing this.<br /><br />Ideas???

 

[KCLOST]

Re: Mariner 150hp advise.

Synthetic will help with the smoke....<br /><br />The rpm issue is a different animal... If it idles rough, it may not be firing properly at higher revs also.<br /><br />Have you checked the fire at the cylinders, also the compression?<br />What prop size/pitch do you have on the motor also? Your motor mount height also affects top rpms...<br />5200 isn't that bad however. Assuming the motor is firing properly and gets fuel, a simple prop change and/or motor height adjustment up can get you a few hundred rpms more easily.(but don't raise it too high, if that's something you may consider).

 

[AndyL]

Re: Mariner 150hp advise.

It is probably no help but my 135 which is essentially the same engine has never idled well. I have had the carbs stripped and checked idle adjustment tweaked and none of it seemed to work. The only thing that made some difference was the fact that the throttle cam was set too close and hence the butterfly valves were slightly opened at idle. The latest thinking was that the stator was weak and that was causing weak sparks hence poor idle. I had the engine for 10 years and have now traded in for a new 150hp. Other than the idle thing my 135 was a superbly reliable engine and I had no hesitation in replacing with the same.<br />Good luck with yours.

 

[POINTER94]

Re: Mariner 150hp advise.

Compression is good and +/- 5% cylinder to cylinder. I had the computers replaced and the plugs look great. Ignition seems fine and I can't remember what the prop is but it is flawless stainless steel rig, three blade, rapture.<br /><br />I know it makes about 52mph with the existing system, and I don't think that I want to go any faster as it will start chine walking at WOT. I am selling/sold the boat and I would very much like to make it as nice as possible for the new owners. They intend to use it for water skiing and the like so raising the outboard isn't exactly what I think they need. Carbs were rebuilt about 2-3 years ago and nothing change there either.<br /><br />I had done a search and this model/year seemed to be prone to this smoking issue. In terms of everything else, I had it dyno'd 3-4 years ago and it made 154hp. Since then nothing has changed. Every once in a while it sounds like it is running on three cyl. but popping some gas (trottle) to it make it go away. Done this for years. Tried to replace the computers to rectify but no luck.<br /><br />It is a v6.<br /><br />Thanks

 

[LubeDude]

Re: Mariner 150hp advise.

If its chine walking at WOT, there is a good chance you need to raise your engine at least a hole. This will get you closer to an acceptable RPM.

 

[KCLOST]

Re: Mariner 150hp advise.

LubeDude knows what he's talking about...<br /><br />My rig will run 60-61mph safely at Wide open, when I try to tilt out to gain more, that's when I chine walk. And my boat is designed to go 70+ mph...<br />The reason I chine walk is because the motor is mounted to low and when tilting out it actualy causes the back of the boat to loose firm pressure on the water (at least that was my understanding). After evaluating the problem, I found I need to raise my motor at least two inches...But if you go that route, raise it an inch at a time and test...<br />I'm running 5100 rpms at WOT with a 4-blade 24p Troph prop, I should gain at least 300-400 by raising it a couple notches....

 

[Truant]

Re: Mariner 150hp advise.

I have 1985 200hp mariner, perfect reco powerhead and just replaced stator ,power packs x 2, rectifier, coils and plugs. Starts well with plenty of smoke, however clean burning at 2000 rpm. However, idles quite rough,I think thats the nature of the beast. Manual suggests yours should top out at5-5500rpm, I get 5,800 ok.<br />Cheers.

 

[gss036]

Re: Mariner 150hp advise.

My 1989 Merc 200 idles rough and my mechanic suggested using high test gas, said that would help it smooth out, but, who can afford to pay over 2 bucks a gallon just to get a smooth idle. I just live with it.<br />90-95% of my running is around 42/4300 RPM.

 

[arboatdr]

Re: Mariner 150hp advise.

Try trimming up you engine slightly when idling for long periods. This will help a lot. Just be sure to trim it back down before planeing out.DH

 

[POINTER94]

Re: Mariner 150hp advise.

Thanks all,<br /><br />Sounds like the nature of the beast. I'll try the synth, and live with what that gives me.

 

[quantumleap]

Re: Mariner 150hp advise.

Also check and see if your secondary exhaust port is submerged at idle, if so trim up til it is unobstructed as arboatdr advised. On My 125 if I'm trimmed all the way down it idles pretty rough but when I bring it up a bit it smooths right out.

 

[KCLOST]

Re: Mariner 150hp advise.

If your upper exhaust ports are partially submerged, your motor is mounted way too low....

 

[quantumleap]

Re: Mariner 150hp advise.

Mine is partially submerged if trim is all the way down. Cav. plate is level with bottom of hull. How is this mounted too low??

 

[arboatdr]

Re: Mariner 150hp advise.

It's common for exaust relief to be below the water line. A lot of bass boats are set up that way. Ideally you want them out of the water but in reality it doesn't always happen.