Seahorse 40 won't throttle up

[toadshade]

Just took my Seahorse out for the first time and after doing minor PM's. It tried to come up to full throttle, but then just sat past idle. It sputtered a little, but what I would expect from an old 2 cycle. It ran fine for quite a while though at high idle. My first thought was the vacuum switch, but it seemed too smooth to be running on one cylinder. At the same time, I am not sure what that would really sound like. I would imagine it would sound terrible. I was in a moving river so I could not spend time trying to get to the throttle on the engine. I will have to put some dog ears on it to see if I could manually increase the throttle. Could simply be a mechanical connection, but any other places to look? This engine is completely new to me.

 

[rat boat]

Definitely check all throttle connection and also the timing/ignition, including the plugs.

 

[toadshade]

Just didn't feel like timing. Yes, an occasional miss, but I wish I knew what a single cylinder sounded/felt like, but it was a nice smooth, but high idle. And when it tried to come up, it was smooth. I putted around for 10 minutes like I was using a 5hp. But I have to admit, it could have been because one cylinder was off. I just assume it would have felt awful to have a cylinder not firing.

 

[racerone]

They will run quite smooth on one cylinder.----Did you replace the fuel pump diaphragm.

 

[jimmbo]

Which 40 hp are you referring to the old 43.9 crossflow from 1960 - 76(and later in commercial form) or the later Loop Charged model?

 

[toadshade]

It is a 1967 (RKL-29) so it must be the crossflow.

And no, I did not replace the fuel diaphram.

 

[racerone]

It sure sounds like it is running on 1 cylinder.----No spark on top or bottom.----And ruptured fuel pump diaphragm.------Both are easy to check out.

 

[toadshade]

Great. I will start there. Thanks a lot

 

[toadshade]

Something I just noticed when I went to get started on the engine this morning. The whole lower unit is covered in patches of oil. It is not lower unit oil. Not blue and that was just replaced. It is above that and black, dripping down the entire thing. Could that also be indicative of a rich mixture, which could point to the punctured diaphram? I am assuming it is rich exhaust oil.

 

[jimmbo]

It could indicate a rich condition in one cylinder due to ruptured diaphragm, it could also mean a high float, or lots of condensate blown out through the Crankcase Drain System, no spark on one Cylinder. Maybe combination of things.
Have you inspected the Spark Plugs?
What Ratio are you mixing the Oil at?

 

[toadshade]

I haven't pulled the plugs yet. Going to do that now. Since it starts up and idles so well, I haven't seen the need to mess with the plugs or even the carb until now. I am using a 50:1. I just ordered a new fuel pump. I went ahead and got a new Sierra 18-7351 based on a discussion I saw here. I guess my pump was not used for long so the Sierra was recommended.

 

[toadshade]

Well, it was a good suggestion to check the cylinders. I never would have thought that engine would run so well on one cylinder. I assume I am getting no spark since the top cylinder looks good and clean, and the bottom is black and oily. Looks like I get to learn how points, magnetos and condensers work. Anyone have a 20hp Honda they aren't using?

 

[racerone]

They marketed some very fine / simple / repairable / easy to maintain motor in the 1960's.-----That 40 HP is a far better motor than you say it is now.------Sorry----If you do not understand these motors you will relegate them to being JUNK.-----Some of the newest parts motors I own are 4 stroke marvels that were deemed " too expensive to repair " by shops

 

[jimmbo]

Those 40s from the 60s were, once they fixed the problem with the Crankshaft-Flywheel were almost Bulletproof engines, many are still running 50+ years later.

Now that you have the plugs out and the engine is easier to crank, verify you have spark, spark that can jump at least 5/16". A fouled plug, gives the same symptom as no spark getting to it
Pull the Flywheel, and inspect the Coils(likely cracked), the points, and the wiring
Far easier to understand, inspect and fix, these Magneto Ignition than any of the newer Electronic Systems,

 

[racerone]

They built / installed that magneto for nearly 40 years.-----A wonderful easy / cheap to maintain unit if you know how and understand how it works.----All the parts can be had new for around $100.-----Try that sum of money with a newer 4 stroke 9.9 Evinrude.----You need more than $1000 to buy all the new ignition parts.-----You just need a few wrenches to bolt those modern motor parts on.-----No knowledge of how they work needed , no adjustment needed..

 

[jimmbo]

The Magneto was fine, but in the 60s changing Plugs on a regular basis because of deposit buildup, was a Big Deal,and often Neglected, so the Self Cleaning Surface Gap was born, but it being very cold actually fouled faster, the cure for that was Higher Voltage and faster Rise Time than the Magnetos at the time could deliver and still have any length of Life for the Points, so that's when the Electronic Ignitions of all kinds were brought in. The different designs had various levels of Reliability and were 'Improved' every couple of Years. though I think most 'Improvements' were really just things that lowered Production Costs, not an Increase in Reliability. Made for some stressed Mechanics with the constant changes, not helped by the insistence of Engine manufacturers requiring specialty Tools instead of more common meters for diagnosis

 

[toadshade]

Yes, I took the flywheel off tonight. I will get into it tomorrow and take a look. It is something that I have hesitated doing since I know nothing about them. But so far, after watching a few YouTube videos on replacing the parts, it looks simple enough. I really enjoy putting all this stuff back in working condition. Jimmbo, what was the crankshaft/flywheel issue you are talking about?

 

[jimmbo]

In 1960 when the 40 was first introduced, there was an issue with the Crankshaft Breaking, It was corrected long before your engine was built

 

[racerone]

If I remember we had one of them with the bigger crankshaft come in.----Crankshaft was broken.-----2 year warranty in those days.------This motor was out of warranty , but factory came good for it and they WANTED that broken crank to study.------The late 60's was a different time than today.

 

[toadshade]

You know, I missed the post by Jimmbo before I wrote my last post. Of course, all my life changing plugs has always been "something you do", but I have never ever been in a position, nor have I heard of anyone I know where a bad plug caused an engine problem. I am going to change this plug and see what happens, but I have the flywheel off now so I will just go ahead and learn this older system. I wish I had tried the plug first. It just never crossed my mind that a plug could cause an issue since it never has before. I just assumed it would be something bigger.