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jody
08-11-2006, 08:42 AM
The problem I have is when I go to take off it is real slow to get on plane. When I give it full throttle it wants to bog the motor, if I pull back a little it quits. To help it get on plane I move forward in the boat it helps some. I still take about 30 seconds to plane out. But once it gets on plane it runs fine. The motor is on a old tri hull bass boat. Not sure of the rpms once I get it to plane out, it doesn,t have a tach. But on the gps it runs 35 mph top speed. Any info would be great.

Thanks Jody
Forkin' Crazy
08-11-2006, 09:01 AM
Sounds to me like you have a dead cylinder or a prop that is way too big. Do a compression test make sure you have ignition spark on all cylinders. What does the tach read?
BigDadys94xj
08-11-2006, 09:31 AM
Check compression and spark first! If everything checks out fine my guess would be either a carb problem or maybe your prop hub is on the way out causing it to spin inside the prop on acceleration. Next time you take the boat out try getting it on plane and as you do hit the choke if the boat starts to accelerate better and plane out with the choke pushed in its time to have the carbs rebuilt because there is some junk in there. I just had 2 70's in here last week with the same problem your describing and both were carb related.
jody
08-11-2006, 09:58 AM
Bigdaddy I tryed what u said about pushing the choke in, when I do that it chokes the motor down. Forkincrazy at this time I don,t have a tach in the boat. I will check compression and spark.


Thanks Jody
BigDadys94xj
08-11-2006, 10:26 AM
do that and lets see the results probably a dead or going dead cylinder.
jody
08-11-2006, 11:03 AM
What should be the compression on this motor?

Jody
Forkin' Crazy
08-11-2006, 11:18 AM
What should be the compression on this motor?

Jody

As long as they are close, like 10% with in each other, that is what you look for. The compression can depend on a lot of things, like year model, head design, etc.

Like was said in a previous post, if the compression and spark are ok, go on to the carbs and check the synchronization of the carb/timing linkage.
jody
08-11-2006, 12:29 PM
Thanks for the info. I'll be back!


Jody
jody
08-13-2006, 08:45 PM
FC and Bigdady, did some checking today. The compression on the top cylinder was 135, middle 125, and botttom was 100lbs. All the cylinders are firing.I did notice that arm that advances the timming was not moving freely so we freed it up.


Jody
BigDadys94xj
08-14-2006, 09:57 AM
Did freeing up the arm for the timing advance take care of your problem?
Forkin' Crazy
08-14-2006, 11:04 AM
Well the timing might just do it, but put it on the muffs/water hose and pull off the plug wires one at a time.... use plastic pliers or a insulated set, or you might get a shock out of it. :eek:

Notice the rpm drop... Also check your coils for cracks.... You can run it at night to see if you have any leaks. If might fire ok at idle, but my jump when you put it under pressure.

If all that fails, it may be in the carbs. You ever check to see what pitch prop you have? Or have you run it before?
jody
08-14-2006, 01:23 PM
I did not get a chance to run the boat after freeing up the arm Bigdady, I will be going to the lake wednesday. FC the prop is a 19 pitch. My dad cleaned out the carbs about a month ago. The boat sat up for about 4 years.


Jody
Mark75H
08-14-2006, 04:52 PM
Problem could lie with the boat as well. It could be hiding water that could be drained out or is permenantly stuck in the wood between the 'glass like a sponge
SportJ-US-1
08-14-2006, 05:09 PM
I don't think 35 mph is out of reason for top speed with a tri-hull with only 70 hp on the transom.
jody
08-14-2006, 08:40 PM
Mark75h I don't think there is any water traped in the wwod, my dad just put new wood in the transome. I guess there could be some in floor area. SportJ I thought 35 was pretty good also. It just takes so long to get on plane. I hope the arm I freed up will solve the problem.


Thanks Jody
jody
08-14-2006, 08:51 PM
I have a old tach I would like to put in the boat, but not shure of how to wire it up. Does any have a wireing diagram to show me how? On the back of the tach there is a dial that has a arrow with the letters A and B, and also the numbers 4, 6, and eight. It also has three terminals S, G, and I.


Thanks Jody
jody
08-14-2006, 08:52 PM
Mark75h I don't think there is any water traped in the wwod, my dad just put new wood in the transome. I guess there could be some in floor area. SportJ I thought 35 was pretty good also. It just takes so long to get on plane. I hope the arm I freed up will solve the problem.


Thanks Jody