Help on an 85' 90 HP ob

[DannyJ]

Hello, everyone I am new to this forum and was wondering if anyone out there could help me. I am considering buying a Crestliner with a 90 hp merc on it. I believe that the motor is an 85. Unfortunately I don't have a model/serial number for it, nor will I have access to the motor until spring. All I know for sure is that the motor is a merc 90 hp inline 6, and I hope that is enough for a start anyway. So here's the scoop. The motor will start and idle like a dream, you can rev it up and it sounds perfect, doesn't hesitate, sputter... nothing. But the second you engage the prop and the motor is under load, you get nothing. Wide open this thing will do about 7 mph. If it is held wide open it will stall. After it stalled the first time I went to the motor and noticed that the cowling was hot to the touch. Rather hot actually. So my first assumption is that the water pump in shot. So now I have 2 questions based on that assumption:<br />1. Can a shot water pump cause the above mentioned symptoms, or is it likely to be something else?<br />2. Is it likely that there was more damage to the motor as a result of us running it, and would it have been immediately apparent?<br /><br />Sorry this is so long and also that I don't have all the required info about the motor, but thanks in advance,<br /><br />Dan

 

[Laddies]

Re: Help on an 85' 90 HP ob

Danny, don't buy anything from anyone unless it's in the water running like you think it should, I see way to many yard sale deals, that only need a little repair turn in to a major repair---Bob

 

[Chris1956]

Re: Help on an 85' 90 HP ob

Danny, What part of the cowling did you touch? It shouldn't be hot to the touch even with a bad waterpump. Did you notice the if the telltale water outlet had any stream?<br /><br />Anyway, the lack of power can occur for many reasons. A failed waterpump can cause significant damage to the compression of the motor. You should check the compression on the cylinders. If the compression is more than 100PSI and all cylinders are within 10 psi of each other, then it is likely carbs and ignition system than need repair.

 

[DannyJ]

Re: Help on an 85' 90 HP ob

Chris, I touched the cowling that wraps around the powerhead. I know that sounds extremely vague, but on this motor, the cowling that wraps the motor is extremely close to all the components. The motor is one of the really tall, skinny buggers if that helps with the mental picture at all. I don't remember if there was stream or not. I know that I am not being the most helpful, but I truly do appreciate all the help.<br />I am kind of tied to this motor and am going to try and fix it one way or another. I found it for the current owner on ebay and have already sunk lots of hours into it, trying to fix other problems. (Wouldn't fire at all) The owner just pretty much wants to be rid of it and if I get it running I can pick it up for next to nothing. If I don't get it running then I will not pick it up. I figure that is the cheapest way to approach the problem.<br />Once we noticed it was hot we shut it off and used the electric motor to get back in, so it wouldn't have been hot for too long. I don't know if that matters or how sensitive these motors are.<br /><br />A mechanic looked at it and everything was kosher with the carburetors. I couldn't tell you exactly what he did to figure that out, only that he told us that was not the problem. As for ignition system we replaced the voltage regulator and the stator, before we could even get the thing to fire.<br /><br />Again thanks so far and any further advise is greatly appreciated.<br /><br />Dan

 

[jimmbo]

Re: Help on an 85' 90 HP ob

Do a compression test on this puppy. and pull the lower unit to replace the water pump. As for the cowl getting hot, being black it will get quite hot just from the sun. I've owned two inlines, a 79 90hp and an 84 115. There is at least an inch, usually more, of clearance between the block and the wrapround. Sync of the spark to the carb, mainly the 1st and secondary pickup is critical on these engines. Flooding carbs due to stuck floats cause more than their share of grief on these engines.

 

[Clams Canino]

Re: Help on an 85' 90 HP ob

I don;t think I can add much here. If the comprssion checks out OK, replace the waterpump and clean the carbs for starters. (good advice for ANY unknown inline 6)<br /><br />-W

 

[DannyJ]

Re: Help on an 85' 90 HP ob

One more question for everyone. Thinking about the spark synching with the carbs, is it possible that when we ordered the stator that we ordered or got the wrong one? I could be mistaken but I thought that the stator controls the spark? (please tell me if I am wrong here)<br /><br />Dan

 

[jimmbo]

Re: Help on an 85' 90 HP ob

The stator generates the current to create the spark. The trigger is what controls it. Part# for the stator was in 1985 parts book 398-5454A17 it might have changed since then. <br /><br />Clams is probably one of the best, if not the best, inline men on the continent.

 

[Clams Canino]

Re: Help on an 85' 90 HP ob

Search the forum here for the "link and sync" post I did. More tuning info than you'll need. <br /><br />-W

 

[DannyJ]

Re: Help on an 85' 90 HP ob

Clams I searched high and low and cound not find your post. If you have a link to it that would be great.<br /><br />Dan

 

[erniex]

Re: Help on an 85' 90 HP ob

Danny,<br /><br />Try this link<br /><br /> http://www.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=29;t=014508#000000

 

[Clams Canino]

Re: Help on an 85' 90 HP ob

Ack! It was "timing and sync" Thanks!!<br /><br />-W