Yanmar Transmission 1993 Hunter 40.5

[rogeronguam]

Hi, I need a new (remanufactured) engine for my 93 Hunter 40.5. I have verified the engine is a Yanmar 4JHBE and the gearbox is a KM4A. I need the reduction gear ratio. Specs I found on the net show ratios of 1.47, 2.14 and 2.63.
Does anyone out know the ratio used in this boat? I am a long way from the engine dealer (Schooner Bay Marine/Imports in Wisconsin). Can't afford to be shipping wrong engine. I sent Hunter a query, but so far no help.
Thanks,
Roger

 

[Bill Roosa]

If all you need is the engine then the gear ratio of the tranny will not matter. The tranny will bolt to the engine no matter what the gear ratio is. Perhaps I'm not understanding what you are doing.

 

[rogeronguam]

Bill,
My trans appears to still be good, but the dealer provides complete remanufactured engines including, the transmission. In this case, I am thinking better to have a new gear box as well (same cost). But, if I can't determine the correct gear ratio, your suggestion might be the way to go. Thanks for the reply.
Roger

 

[Ron20324]

Isn't there an info plate on top of the tranny?

 

[Rich Stidger]

Do you have a friend near your boat that could check for you?
I take pictures of everything, and especially when I do a repair job to document how I accomplished the task. That way I can look and often see the information that I need. Of course there are lots of times when I don't have a picture- no system is perfect. But pictures could help you in the future.

 

[smokey73]

I've got a 1994 40.5 built in 1993. My hull number is HUN40570F394. My engine is a 4JH2E rated at 50HP at 3600 rpm. I'm not sure of the 4JHBE you refer to, is that a typo and its a 2 instead of a B? If its the same engine as mine I'll get some info off the tranny in a few days when I go to the boat to check on some things.

 

[rogeronguam]

There is a plate, but it just list the trans model (KM4A)and has another number (6078), which we think might be a serial number. There are no other plates on the trans.

 

[rogeronguam]

Yup, should have taken pics when the engine was pulled a couple of yeas ago, but sure will this time. Thanks, Roger

 

[rogeronguam]

Smokey,
That sounds great. I did make a mistake on the engine. It is a 4JH2BE. From my research, the 2 is a newer model than the plain "E" model. The "B" indicates a 10 degree down angle trans. Is your boat a 2 or 3 cabin setup? Mine is 3 cabin, hull # HUN40526J293. Not sure if the 2 cabin would have an in-line, vice down angle, trans, but I would think the gear ratio's should be the same. Appreciate your help.
Roger

 

[smokey73]

Mine is a two cabin setup (large aft cabin with the aft bunk athwartships. I can't imagine that the gear ratios would be different since the objective is get the correct revs at the prop based on the engine characteristics. With the 50HP at 3600 rpm, assuming you had the same original prop, it would seem the gear ratio should be based on that combination.

 

[rogeronguam]

I would assume the ratios would be the same. Can't believe the cabin setup would make any difference. I never ran my engine over 3000 rpm, pushed boat at hull speed. I sure wish I had the cabin setup, but got mine via a charter deal. Great boat, but really wish I had the big owner cabin. Wondering if the trans would be different (straight through or down angle)? Would not think so. Appreciate your help. Last choice would be just replace the engine and keep the old trans, but would rather replace everything since cost will be the same. I attached an intersting page from web that explains Yanmar engine nomenclatures.

 

[Rich Stidger]

If you have the transmission model number and the serial number, perhaps the manufacturer can tell you the ratio. Or as a "Plan B" you could order the new engine with the most likely transmission ratio and then compare it to your OEM transmission before installation.

If the query you sent Hunter was an email, why don't you just pick up the phone and call them. Email is fine if you need a written record or are not in a hurry, but a direct phone call can be more expedient- at least if you don't get trapped in phone menu hell.

 

[Ron20324]

Another forum says the plate could be on the front OR the back of the tranny. This would be a different plate from the one on the top.

 

[rogeronguam]

Thanks Rich. I have been off-line the last couple of weeks, just read your reply. Guess I will try to give Hunter a call. It's a little inconvenient given the time zone differences, but that is my next step. Alternatively, as you suggested, I may just order the engine with the mid of the 3 available ratios. If the ratio is not the same, I don't think it would be too difficult to change the gears. I assume the part most subject to wear would be the clutch. Or, just keep the old trans that seems to be OK. The dealer suggested to remove the trans and measure the ratio. Not difficult except for having to remove the engine before ordering. I am sitting in a slip. Removing the engine is not a simple matter, but I am looking at doing it. Thanks again for suggestions. Would be nice if we had a real marina with Hunter/Yanmar support, but we don't. No boat yard facilities at all out here.
Thanks, Roger

 

[rogeronguam]

All I have to do is pull the engine. May comedown to that, but I'm in a slip, no facilities, I was hoping to only have to disassemble the cover and pull the engine once. Might need to, thanks for the reply. Roger

 

[whatfiero]

Your making this way to complicated go to boat with magic marker and big socket set 3/4 7/8 1" . expose shaft in aft cabin under floor boards. Expose front engine. Mark shaft with marker Mark engine harmonic balancer or rotate to tdi. Put tranny in forward and pull engine shut off. Engage compression release valves if you have rotate engine 1 time check shaft Mark has it almost come into view that's the 1.75 tranny. Rotate again. Is is real close to original location that's the 2.15 tranny. If Ya got to go another half turn then you at the 2.6 range

 

[rogeronguam]

The engine is frozen.

 

[Rich Stidger]

The engine is frozen.

Can you have your boat towed to a warmer climate so the engine will thaw? I know, totally unhelpful but I couldn't resist.

Seriously, I would do one of the following, listed in order of preference:
1. Call Hunter with boat serial number, engine S/N, and transmission numbers.
2. Look in the owners directory for who owns another 1993 h40.5. I looked and there are several dozen 1993 models. Find members that are in a warm climate because their boats probably will be in service and not winterized. Contact each one directly and ask them to confirm the same prop size as you and then ask them to measure their ratio. I have to think that there is someone who has the ability and time to do this favor.
3. Is there any way that you can disconnect the transmission, push the prop shaft aft and remove the transmission? It looks like the transmission has an input splined shaft that fits into the crank. You may only need to move the transmission back a couple inches to dis-engage. Or since you have to remove the engine anyway, can you move the engine forward a couple inches to get the same clearance? Then just leave the engine there until you do the swap.
4. One of the transmission manuals that I was looking at specified the recommended ratio based upon the prop pitch and diameter. If you know the size of your prop perhaps that will give the answer.
5. KM4B transmission manuals show the transmission plate with a spot for the ratio to be stamped. Are you absolutely sure that your plate is missing this info? Maybe it is faint and hard to see?

 

[Rich Stidger]

Here is the table of ratio for prop sizes that I found:

This table was in this document:
http://www.hughes38.com/wp-content/uploads/2016/02/KM-Series-Service-Manual-incl-KM35P.pdf

 

[Bill Roosa]

To Rich's comment; can you un freeze it? Do we know why it is frozen? A bad case of cranking in cold weather can freeze and engine due to hydro lock and there be absolutely nothing wrong with the engine. I've saved a couple of rusted engines with a crankshaft pulley socket, breaker bar and baby sledge hammer. A cautionary note: impact modulation is not banging it with a hammer. Impact modulation is the scientific application of a hammer to solve a problem and never results in broken parts. Banging is non scientific and results in broken parts. Experience is what a novice gets when he thinks he is doing impact modulation but he is really just banging ;-)