Thread: Mariner 150 w/personality

A few months back I bought this boat with a 150 mariner, this is my first big motor. 40hp was tops til now, so I know little. My problem; most of the time the motor starts ok, but when it's time to go fish, push throttle wide open to get on a plane, and I'm missing a cylinder. Runs like that to first hole of the day. After fishing for an hour or so, fire it up and it may still be missing. but very soon into the ride to hole #2, the miss will begin to fire and do so for the rest of the day. Paid to have carbs rebuilt(bought kits) and needles and seats replaced, not free. Had it back to the mechanic twice now and get nothing but a song and dance.he looks it over, warm by this time and says he's had it to the lake, runs great he says. Lately it's missing 2 cylinders, won't get up on a plane. Disappointed would be an understatement. Not so much with the motor, it's a machine and can and will be fixed. The treatment by the tech and shop owner is about to get under my skin. Looked today and I can't see any wrench marks on the carb area bolts and the ty wraps don't look to have been bothered. I have two questions for y'all. First, do I take it to another mechanic and see if the works been done as I've been told. Second, if the work has not been done, how to handle it. I know the obvious answer to the second, so please don't throw gas on the fire. Please give me any serious input you may have, falls comin soon. If you've had a problem like this, tell me where to look. Thanx.....Tim

i would presume they did a compression check on the engine. I had the exact same thing happen to me on a used boat I recently bought. when I started it, ran fine. after the engine warms up, won't idle, won't plane out consistently on take off and misses.

When I got a compression check, no cylinders over 80lbs, and 2 cylinders at 60. should run 120 - 140lbs per cylinder. wound up having to have the powerhead overhauled, and it's not cheap. this may not be your problem, but if you haven't checked compression, a kit to do it is cheap.

the way to check compression is undo all sparkplug wires and test each cylinder by hooking up the kit to the hole for spark plug. turn engine over for 3 seconds and it should tell you.

In my case what happened was the cylinders & pistons were pitted up and scored, gasket burned up, etc. best estimation was the pump that mixes oil & gas went out on the oil side, and engine stopped burning mixed gas. prior owner must have caught it in time, and now mixed gas & oil in the tank. decided to unload boat instead of fixing engine.

I learned a valuable lesson, ALWAYS do a compression check on a used engine before you buy it. can tell you if there are major powerhead issues with any boat.

I hope this is not the problem, but this sounds very familiar to my story. hope this helps.

I posted the last post before going to a well respected and referred mechanic that 2 of my club brothers had used in the past. Compression is right, 120 down the line. Trigger and possibly power packs are the main focus right now. He'll check the other stuff once there is a hot spark. The spark was weak on the working cylinders and not fully burning all the fuel/oil mixture causing the frequent fouling of plugs I was experiencing. This tech is straight up. Shows you the book, the meter showing diminished values of the electronic parts, Compression gauge, spark card, no secrets. It's gonna cost me a few more $ but it will be right or it won't leave his shop is his promise. Thanks for the input. Another lesson learned along the way, pricier than I'd hoped. For a first big motor I'm still not doin too bad.

Well at least now you will have confidence in your new motor. Oh while he has motor U may want to have him check/change water pump impeller as it sounds like previous owner wasn't too up on maintenance, those gotta be changed every several years & good fall fishing to ya.............

an honest mechanic can be hard to come by. I was extremely lucky to find the guy that fixed my boat. It's working great. good luck. hope it works out.

I had the same problem a few years ago with my 50 hp Merc.
Turned out to be the brain. I guess there are two parts to it, one low
speed which was ok and high speed which was not. $200 to replace it and no problems since. Symptoms were the same as you mentioned.

What year is the motor?

'88 and the impeller and oil pump were done along with carbs when the first guy worked on it. Had he checked everything he would have caught this other stuff.

I just wanted to post the finish on here so y'all know how it ended. Trigger was junk, and it can take out the power packs. So not wanting to gamble any more than I had to, I had him order a new trigger. One power pack had to be replaced. Reset the timing and go over the rest of the tuning adjustments and I'm told it's running real strong. He has already had it to the lake, and I'll pick it up tomorrow. Now, when's that next tournament?