Need some advice on my 60hp 2 stroke

[artilarygoboom]

So I have a 15' 74 starcraft trihull, and it has a 2 stroke 60hp merc on it, i looked up the serial number and it seems to be a 1985 i think. my boat does not weigh that much, not sure of the exact weight, ill look to see if i can find it tommorrow but I am not sure if my prop is to small or the wrong one or if its running right. my boat at WOT only goes 10 mph. which i think is really low considering my uncles's 90hp that he had on a 18ft cuddy did 40 at wot 2 stroke as well. The engine was apparently rebuilt last season, i just bought the boat this week, any advice? the engine runs pretty smooth but i think its more of a prop problem

 

[artilarygoboom]

Re: Need some advice on my 60hp 2 stroke

so i got my propeller off and its stamped 48-73136 a40 13p and theres a 14 stamped in the center were the hub is. would i be able to put a slight bigger propellar on for more top end?

 

[BonairII]

Re: Need some advice on my 60hp 2 stroke

It's definitely NOT a prop problem. 10mph at WOT means that you probably have a cyl(s) not firing.

 

[GA_Boater]

Re: Need some advice on my 60hp 2 stroke

If you have a tach, what RPM are your turning at WOT? Should be in the area of 4800-5200 RPM, give or take.

 

[artilarygoboom]

Re: Need some advice on my 60hp 2 stroke

i dont have a tach but i think im gonna order one of those small ones that you wrap around your spark plug wire to get the rpm, so i pulled off my engine cover and pulled the spark plugs, i noticed one of the spark boot is ripped and was wrapped with electrical take and on the side of the spark plug i see a small black mark like the spark was arcking off the porcelain. the spark plugs looked good except for one, i believe its number 3, looked to have alot of carbon build up on it. the ripped spark plug boot was the very top cylinder. Also another thing is my power/tilt is not working at the moment so its just set all the way down, and i cant tilt it up alittle so can that drasticly effect speed? also were can i get a set of replacement spark plug wires and plugs?

 

[BonairII]

Re: Need some advice on my 60hp 2 stroke

i dont have a tach but i think im gonna order one of those small ones that you wrap around your spark plug wire to get the rpm,

You're probably referring to a "tinytach". They are good from what I hear, but if I were you I'd spend another $20 and get a tach that installs at the helm. That way you can read RPM while your underway instead of having to have someone drive while you're back at the motor trying to read the tach.

 

[artilarygoboom]

Re: Need some advice on my 60hp 2 stroke

what tach is that cheap that you can install in the helm? do you have a link?

 

[oldman570]

Re: Need some advice on my 60hp 2 stroke

Definately sounds like a motor problem to me. That boat motor combination should be able to run near 25 to 30 with a 15 pitch prop. Best to use a timming light and check for spark on all the plug wires, then a compression test, and new spark plugs and wires if compression is good. Test for a spun prop also. Running a motor on muffs will not show a bad or missing cylinder as the backpressure on the exhaust is not there .
Oldman570

 

[BonairII]

Re: Need some advice on my 60hp 2 stroke

what tach is that cheap that you can install in the helm? do you have a link?

I bought this one(in black not arctic white)
http://www.basspro.com/Teleflex-Mar...hopping_googlebase&om_mmc=shopping_googlebase

A genuine "TinyTach" is $50.

A good tach will pay for itself by helping you diagnose motor problems and save you the money of buying the wrong prop(s).

 

[artilarygoboom]

Re: Need some advice on my 60hp 2 stroke

so ive been doing some more searching and im starting to think that i am running on 2 instead of 3 cylinders. Ive also read it can sometimes be hard to hear a misfire on a 2 stroke, my motor sounds like its running fine but when i go full throttle it is sluggish now that i think about it. If I am running on 2 cylinders and 1 is not burning fuel will it cause the piston to burn like in a 4 stroke? or will the oil/fuel that is still going in the cylinder keep it lubricated? Were can i get a set of 3 spark plug wires? I looked online and see they only sell 1 wire at a time and not as a set.

 

[oldman570]

Re: Need some advice on my 60hp 2 stroke

A plug not firing should not hurt the piston as the oil and gas is not being burnt. As for the plug wires you can buy soild wire core wire by the foot at most auto stores and make your wires as needed. Some dielectric grease on the conections will keep crrosion at bay when used. Anytime you turn the motor over with the plug wires disconscted they have to be grounded out or you can damage the switchbox and other items of the electral system. Test the coils and stator by switching wires on the switchbox and checking the spark at the plugs will eleminate the coils and stator. The switchboxes have been known to go bad on motors as yours. A good service manual will have testing methiods in it for testing most all units involved in the ignication system.
Oldman570

 

[artilarygoboom]

Re: Need some advice on my 60hp 2 stroke

so i just did a compression check and 2 cylinders are at 120psi and 1 is at 90 psi...im kinda upset about this. is 90psi still to low? My guess is this guy lied to me and the motor was never rebuilt. the cylinder with 90 psi seemed to have the most carbon on the spark plug to. What do you guys reccomend, im about to call this guy and tell him to give me my money back and take ur boat back. just want some info before i do.

 

[BonairII]

Re: Need some advice on my 60hp 2 stroke

I doubt the seller will take it back. He'll claim that you caused the damage.

You can start by trying a "decarb"(very easy procedure btw) on the motor to clear the cyls/heads/rings of carbon deposits...you might just have a stuck ring.

If that doesn't help, pull the head and check for visible damage. If no damage, it might just have a leaking head gasket. Just replace the gasket(and torque to manufacturer specs).

90psi isn't "too low" per se, but you really want all cyls to within 10% of each other.

 

[artilarygoboom]

Re: Need some advice on my 60hp 2 stroke

well couple things ive done so far, i tested for spark in all 3 cylinders to make sure my coils are working and i got spark in all 3, im changing out my spark plugs while im in there, and i put mystery oil in the 3rd cylinder which was the low one and have it sitting there for a couple hours and then ill re check the compression. Is there a write up on how to decarb the engine? and how hard is it to do the head gasket and were can i get a replacement gasket? im new to this boating thing but I am pretty good with tools and mechanic type of stuff sine i am a toyota mechanic by profession. But carbs and 2 strokes and outboards is all new to me. I appreciate all the help

 

[artilarygoboom]

Re: Need some advice on my 60hp 2 stroke

ok another update, after letting the cylinder sit in mystery oil and moving the flywheel back and forth for 30 min the compression test came back at 100-105 which is better, so i put more in and gonna let it sit over night.

Discovered another problem since i got curious about the carberators, i took off the carb cover to look inside the butterflys to see if there was alot of gunk in there and when i put the throttle all the way foward only 1 of the 2 carbs opened up. So now i have one carb shut which would explain why the motor sounded like it was struggling and problaby flooding since no air was getting in. i was trying to look to see if theres a linkage somewere that is not hooked up but im so unfamiliar with the set up i dont realy see anything, can anyone point me in the rite direction here?

 

[artilarygoboom]

Re: Need some advice on my 60hp 2 stroke

also the engine has been converted to premix and is no longer oil injected :/ idk if that may have something to do with the second butterfly not opening but i dont think it should

 

[GA_Boater]

Re: Need some advice on my 60hp 2 stroke

Two things;

1) Do the butterflies on both carbs fully open and move together.

2) Y'all pay too much for stuff. $18 + shipping tach. It works great. And it will for your 60 hp too. EDIT - As long as it's 12 pole.

 

[artilarygoboom]

Re: Need some advice on my 60hp 2 stroke

no the carbs do not open together, only the top one opens all the way, the bottom carb stays closed.

 

[GA_Boater]

Re: Need some advice on my 60hp 2 stroke

no the carbs do not open together, only the top one opens all the way, the bottom carb stays closed.

There's your problem. Or one of them any way. Do you have a manual? You're gonna need one.

 

[artilarygoboom]

Re: Need some advice on my 60hp 2 stroke

no i dont have a manual..were can i get one? i saw a used set of carbs on ebay but im sure i will still have the same problem is i just put a diffrent set of carbs on. is there a linkage linking both of them together? i dont really see anything thats missing