Shaky low speed on Faststrike 150

[Rustyhook]

Last couple of runs my Faststrike acted a little funny. 1992 Johnson 150 Faststrike J150GLEN

After a good run at WOT or close to it, I bring the rpms down to around a 1000rpms to slow it down (still in gear). The motor idles a little rough and shakes. When I put it in neutral, all is fine and it idles smooth.

I will shut it down for awhile (1hr or more), fire it up (idles fine), drop the hammer and take off (accelerates great and WOT is good), but when I slow it down I get the shaky stuff again.

Temp is good. I've been blaming it on bad gas.

Any ideas?
Thanks,
Rustyhook
Riley KS

[rudetech1]

Check to see if you have brown gaskets behind the intake manifold.If not . You need to get the fuel system reworked. New check valves,new gaskets, and possibly carb kits if they have not been rebiult since 95'. The gaskets react with the fuel and cut off fuel flow, the old check valves disintegrate, the carb nozzle gaskets swell off the bosses on 91' to 94' 6v6. If you are in doubt, take it to a competent technitian. Instead of the check valves, its easier to change the intake manifolds. There are check valves in the block that will also need servicing, they sit behind the manifold.

[sapnfish]

Why a brown gasket behind the carbs?

[Mr.Rude]

Have you checked the switch located on the shifter linkage. I have no idea what it is there for, retarding timing for some reason it seems. But, mine broke on my 92 150 and was getting depress when it should not have been. It runs awful when pressed. I just taped it out of the way and kept on keepin' on

[SEAHORSE]

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by sapnfish &raquo;</TD></TR><TR><TD CLASS="quote">Why a brown gasket behind the carbs? </TD></TR></TABLE>

The old black intake manifold gaskets, I believe they were discontiued in 1993, would swell up with the chemicals in today's gasoline and restricted the fuel flow.

Also check, or have a tech check, the synch and link of the carbs, and to be sure the throttle roller is not broken, missing, or delaminated.

[Rustyhook]

Check valves,
I located these on the BRP website diagram.

I assume these are for the transition fuel flow from off idle with a load (butterflies still shut). This would make sense, because the engine idles great with all the plates shut, but when they are shut with a load (in gear at idle) I have the problem.

Question is, how many check valves are there, six? How many are in the block?

Thanks,
Rustyhook
Riley KS

[rudetech1]

Thes check valves are the fuel reciculation system, they keep the fuel from puddling at the leaf vaves. If they do not work , the fuel runs from rich to lean, and visa versa. It's all about keeping the fuel going in 1 direction. You have a great engine, you just need some work to improve it. This was the peach of the industry when it came out. Unfotunately, the changes to the fuel additives were hard on the synthetic components. They have way better synthetic components now. By synthetic, I mean the additives to the rubber type components and the plastics. Good luck.

[Rustyhook]

Thanks for the replies. I have done a lot of work on this motor already (improvement to fuel componets; hoses, clamps, filters, and such) it makes to sense to fix it all. I do all my own work and I have a good connection to BRP parts and help if needed.

Last year I did some of the same stuff to an older 40hp Johnson (except checkvalves). I noticed the new gaskets were mostly brown.

Thanks again,
Rustyhook
Riley KS