1987 mariner 150 no low to midrange power

[Ryan618]

I just got a 1986 cheetah fish & ski with a 1987 mariner 150 on it. I took it out for the first time today, it fired right up and had good throttle response at low RPM's but once I got out of the no wake zone and started to take off the engine started surging/cutting out, not real sure which is more accurate, once the RPM's finally climbed up it ran great on the top end with the engine trimmed up a bit. There seems to be a lot of hesitation when accelerating from a stop or no wake zone speeds. It seems that it would be a fuel delivery issue but I'm not sure where to start, not a lot of experience with 2 stroke engines.

Also, the throttle control will not stay in position on its own, i have to hold it in position which isn't terrible but i had this same throttle control in a celebrity years ago and it always stayed in position.

Thanks for any thoughts or advice, by the way, I do have a manual previous owner gave me but it covers all 1987 mariner engines, not sure if this is a good one or not.

 

[hkeiner]

Re: 1987 mariner 150 no low to midrange power

There are a lot of possibilities and I can only guess at the problem without any troubleshooting info. My first guess is that the idle jets on the carbs need adjusting or the carbs need cleaning.

However, I would suggest that you do some systematic troubleshooting to narrow down the problem. First check the compression and spark on all cylinders. Then adjust the idle jets to see if that helps any. Then clean the carbs to make sure they are not gummed up or the floats missadjusted. Also,, confirm that the link and sync is correct. Another test is to connect a portable tank with fresh gas to the motor to eliminate possible problems (line restrictions, water in fuel, etc.) with the fuel supply from the onboard fuel tank.

If you do all of the above and the problem does not go away, report back on what you did find and you will probably get advice that is better than a guess.

 

[j_martin]

Re: 1987 mariner 150 no low to midrange power

That boat probably has WH carbs on it, which won't have an idle adjustment on it. Doesn't sound like idle anyway.

If it idles well, it probably has good compression. It might be worth checking just to eliminate major engine problems from the possible faults list.

With modern fuel, a boat sitting for any time is at the mercy of several perils. Fuel separation is one of them. Neither the water/alcohol crud at the bottom, or the now low octane fuel that's left will burn well. Also, this same scenario breeds critters in the fuel tank that generate a sludge that wrecks havoc on the fuel system.

If bad gas is suspect, clean it out and just go through the entire fuel system. It really isn't all that much. Primer bulb and hose. (a sawbuck) Fuel pump kit. (another one) Internal fuel lines. ('nother one) Carb kits. (3 more), Carb base gaskets (few bucks), fuel filter, about 130 bucks altogether for parts.

The best way to prove fuel delivery problems is to rig a pressure gauge to the carburetor fuel rail. Use about a 15 psi gauge. Each carb has 2 threaded ports for fuel inlet, on on each side. They are usually daisy-chained together, leaving one left, with a pipe plug in it. If you remove that plug and replace it with a hose barb, you can hook up a pressure gauge.

Don't try to run it much till you get the problem solved. Fuel starvation is one of the quickest ways to burn one of the big bad boys down for good.

All of this is assuming you don't have oil system problems. If pre-mix, oil at 50:1. If injected, hear test beeps when you turn the key on, then no beeping when it's running.

hope it helps
John

 

[Ryan618]

Re: 1987 mariner 150 no low to midrange power

Thanks for all the tips, tried a few and it seems to be running great now, checked the fuel pressure and it was good, put a new set of plugs in, ran some seafoam through a tank of gas and it's running like a champ!